The Secret of the Baltic

Roy Glashan's Library
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T.C. BRIDGES

THE SECRET OF THE BALTIC

WITH FOUR OOLOUR PLATES BY DUDLEY TENNANT (1867-1952)

First published by William Collins, London, 1919
Collins Clear-Type Press edition (this version), 1920

This e-book edition: Roy Glashan's Library, 2021
Version Date: 2021-03-26
Produced by Keith Emmett and Roy Glashan

All content added by RGL is proprietary and protected by copyright.

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CHAPTER I. THE MAN FROM THE SKY
CHAPTER II. VON FROMACH'S SECOND TRY
CHAPTER III. DICK ANSON'S STORY
CHAPTER IV. AN UGLY SHOCK
CHAPTER V. WAYLAID!
CHAPTER VI. THE 'DUG-OUT'
CHAPTER VII. THE FIRST SHELL
CHAPTER VIII. STAPYLTON'S PROMISE
CHAPTER IX. THE KIDNAPPING OF WALLACE INGRAM
CHAPTER X. THE HUN OFFERS TERMS
CHAPTER XI. FRESH TREACHERY
CHAPTER XII. THE DETECTOR
CHAPTER XIII. ON THE TRAIL
CHAPTER XIV. IN THE STRAITS
CHAPTER XV. DODGING A DEPTH CHARGE
CHAPTER XVI. NOSING HOME
CHAPTER XVII. A MORNING CALL
CHAPTER XVIII. POISON GAS
CHAPTER XIX. X1 SAILS
CHAPTER XX. THE STRICKEN CRUISER
CHAPTER XXI. GUY GOES OVERBOARD
CHAPTER XXII. FACE TO FACE

LIST OF ILLUSTRATIONS

Illustration 1. Frontispiece: "Close call!' gasped Anson.
Illustration 2. There was a shattering crash.
Illustration 3. The giant gas-bag had split like a soap bubble.
Illustration 4. Penruddocke and Guy had fired the electric gun.

CHAPTER I
THE MAN FROM THE SKY

Guy Hallam glanced down at the little gray North Sea waves that creamed and gurgled at the foot of the bare rocks; then his glance wandered across the bleak stretches of Yorkshire moorland running inland to the sky line.

'Couldn't be better, Wally. There's nothing to damage except a few gulls and crows, or perhaps—' He stopped suddenly and frowned slightly.

'Cratch, you mean?' said Wallace Ingram sharply. 'You are thinking of that beggar, Cratch, Guy?'

'I was,' confessed Guy. 'Fact is, I've been thinking a whole lot about the swab.'

'Serve him right if he is here,' said Wallace, with a viciousness quite startling in such a cheery, chubby-faced youngster. 'Serve him right if he is in the very centre of the pressure area. If he is, it's the last time he'll do any spying. That's one thing sure.'

Guy Hallam chuckled rather grimly. 'Yes, there won't be much left of him. And, like you, I couldn't find it in my heart to be sorry. Though we have no proof, it's a sure thing that Cratch is up to no good. He'd never have settled in a place like this if it hadn't been to spy on your father. Well, he'll have to take his chance. I don't see the flag up yet, Wally.'

'There's no hurry. We may just as well wait until he is ready. I don't suppose he thinks we are here yet.'

'He can't get it into his head that you can plug along as fast as you do, Guy,' said Wallace, with a laugh. 'For a chap with a game leg you're a holy wonder. Why, it takes me all I know to keep up with you.'

Guy did not smile. His lameness, caused by an accident in a fire at school when he had risked his life to save another boy, was a terribly sore point with him. Although at eighteen he was taller, stronger, deeper in the chest and broader in the shoulders than most grown men, yet that damaged leg and the slight limp resulting from it had cut him off from the chance of wearing His Majesty's uniform. That was why he had turned all his thoughts and brains to chemistry and was now helping Wallace's father to perfect his inventions—inventions which, if properly used, would, so Mr Ingram hoped, do more to smash Germany than a dozen army corps or a fleet of battleships.

Young Wallace saw that he had put his foot in it, and very sensibly changed the subject.

Guy shook his head. 'It's going to be a tough job,' he answered. 'An unknown man always has the hardest kind of work to get any one big to take interest in a new invention. And neonite is so amazingly new and startling that no one would ever believe what it can do unless they saw it in action.'

'And the gun is just as wonderful,' said Wallace. 'Dad says that, if he had the money, he could make one that would shoot from Paris to Cologne.'

'And so he could,' declared Guy, 'or to Berlin either. It's only a question of sufficient power. Given the power, there is no limit. You could copy Jules Verne and shoot a projectile from the earth to the moon.'

'I suppose you could,' agreed Wallace. He turned and glanced towards the low, gray-walled, slate-roofed house that stood against the hill-side a mile away across the bay.

He pointed upwards as he spoke, and Wallace, looking up into the sky, saw an object floating at an enormous height above them. It was long and thin, and showed a delicate silver-gray against the pale blue summer sky. It was still over the sea, but was moving towards them at a brisk pace. Clearly a strong easterly current of air was setting up above, though below the light breeze was northerly.

'That's what I thought,' Guy answered. 'One of those observation balloons they use on the Front. She must have broken loose. But how on earth she has come right up here so far north is a puzzle to me.'

'It is a bit startling,' replied Wallace, still staring upwards. For the moment both of them had clean forgotten the trial of the neonite. 'I wonder if there's any one in her.'

'Hardly likely,' said Guy. 'Observers have parachutes, you know. Then if anything goes wrong, they can jump overboard and land.'

There was silence for a few moments, while the balloon came steadily nearer. As she approached she grew larger.

'She's coming lower, Guy,' said Wallace. 'That looks as if there was some one in her, letting out the gas.'

'You're right,' replied Guy. 'You're right, Wally. There is some one in the car. I can see him moving.'

'What's he doing?' exclaimed Wallace. 'What on earth is he about? Look! Look!' he continued, in a tone of horror. 'He's throwing himself out.'

'It hasn't opened. He's dropping,' gasped the younger of the two. 'Guy, it's ghastly! He'll be smashed to pulp.'

'It's all right, I tell you, Wally. There, it's opening now. See, like an umbrella. He knows what he's about.'

Wallace drew a long breath of relief. After dropping like a plummet for several hundred feet the parachute had at last opened, and now the man from the balloon was dropping quite slowly, swaying slightly from one side to the other as he came. The balloon, meantime, relieved of his weight, had soared upwards again until it was a mere speck in the sky.

The boys hardly noticed it. Their eyes were glued upon the parachute. It was now beneath the easterly current, and in the lower drift of air.

'I say, Guy,' said Wallace anxiously. 'I don't believe he'll ever reach the land. He'll drop into the sea.'

'Just what I was afraid of,' answered Guy. 'But don't worry, we'll have him out.'

As he spoke he was over the edge of the bluff, and clambering down towards the sea.

'No, stay where you are,' he called. 'And signal to your father to hold up the explosion till we give the word.'

Guy might be lame, but precious few sound men could have beaten him in a race down that bluff. Though not very high, it was steep, and the rocks were sharp and ugly. Fortunately the tide was low, and there was a narrow strip of shingle lying bare at the foot of the cliff. Reaching this, Guy looked up.

There was the parachute not a hundred feet up, fluttering downwards quite slowly and gently. And the man who sat in the loop wore the uniform of a British naval officer.

'Thank goodness, he won't fall very far out,' said Guy, measuring the distance with his eyes. Then, flinging off coat and waistcoat, he plunged into the water.

He timed it so well that, as the dangling sailor touched the water, he was exactly beneath. The sailor had already got clear of the loop and was hanging on to the rope by his hands.

Looking up, Guy caught a glimpse of a face brown almost as old saddle leather, but pinched with cold and perhaps hunger, gray eyes reddened with wind and fatigue, and a chin of the type which is generally described as being 'like the toe of a boot.'

'I say, this is awfully good of you,' said the stranger hoarsely, as he dropped almost into Guy's arms. 'But I can swim all right.'

'Dare say you can,' responded Guy dryly. 'But not in Galleon Gap. Currents here are no joke, I can tell you. Let yourself float. I'll tow you in. Then I'll get the parachute.'

'Blow the parachute,' said the other. 'Let it go. It's only a Hun one anyhow. Jove, I'm not sorry you came out! I don't mind owning I'm pretty near done.'

Guy did not answer. He had his work cut out. The tide, still ebbing, sucked him treacherously away from the shore. He was forced to fight with all his strength and cunning, and as for the stranger, he would not have had a dog's chance alone.

'My only aunt, but you're some swimmer!' gasped the other, as Guy found his feet and dragged him ashore. 'Ugh, isn't the water cold?'

'I've been up topside the last twelve hours and more,' he added apologetically. 'And not even a pea-jacket to keep the chill out.'

'Twelve hours! I should jolly well think you had had enough of it,' answered Guy. 'But you'll be all right now. Do you feel up to climbing the rocks, or shall we go round by the path?'

'The path, I think, if you don't mind,' said the other, trying to smile, but making rather a poor attempt at it. Guy saw he could hardly stand, and made no bones about getting an arm round him and helping him along.

'Chuck that!' said the other quickly. 'Hang it all, man, you can't help me. You've hurt yourself. You are limping.'

'I've been limping these four years,' replied Guy, rather grimly. 'There's nothing to make a song about.'

'I—I'm sorry,' said the other hastily. 'I say, I haven't introduced myself. I'm Anson—Dick Anson.'

'Guy Hallam, I'm called,' replied Guy, more genially. 'And I'm living at that house across the bay. It's just as well you dropped where you did. There isn't another house for miles except—'

'That youngster at the top of the cliff,' said Anson. 'There's something up. What's he pointing at?'

He turned as he spoke and looked upwards, in the direction in which Wallace Ingram was pointing.

'A plane!' he exclaimed, and his voice was suddenly sharp. 'Look out, Hallam! They're after me, I do believe. We'd better take cover.'

'What's the matter?' asked Guy, in surprise. 'She's one of ours. Look at her marks.'

'Then what is she doing here?' demanded Anson. Guy was surprised to see how anxious—almost scared—the young sailor seemed to be. He was still more amazed to see him break away and fling himself down behind a rock.

'Get in here,' cried Anson sharply. 'Lie down beside me. Quick! I tell you she's a Hun.'

Guy stood staring up at the plane. 'She can't be,' he remonstrated. 'Look at her red white and blue circles.'

Anson sprang up again, caught Guy by the arm, and with a strength Guy did not suspect he possessed, dragged him down behind the rock.

'Camouflage, I tell you,' he said roughly. 'She's a Hun, and she's after me. See! She's coming straight down.'

She certainly was. Her pilot had cut out the engine, and in perfect silence she was sweeping downwards in a long steep glide. She was a very large seaplane. Her double planes were quite a hundred feet from tip to tip, and her fuselage appeared to be armoured. She had two tractors, and between their spinning blades Guy caught sight of the black muzzle of a machine gun. She bore a sinister resemblance to a gigantic bird of prey swooping down out of the blue.

'After you!' echoed Guy. Then, before he could say anything more, the silence was split by the sharp rattle of the machine gun, and a storm of bullets lashed the cliff side all around them. Splinters of rock flew in every direction, and the dust was blinding.

The burst was over in a matter of seconds, but it lasted long enough for Guy to be certain that, if Anson had not forced him to take cover, he would have been riddled like a sieve. Next instant the twin engines roared again, and the plane, circling, zoomed upwards, preparatory to a second dive and fire burst. Guy raised himself a little and stared up at her.

'Get down!' shouted Anson in Guy's ear. 'Lie low, I tell you. Hang it all, man, don't you realise by this time that I know what I'm talking about? I tell you they'd sell their souls to get me. I'm the only man in England who knows their big secret.'

'But Wallace!' he cried, in desperate anxiety. 'Heavens, man, the brutes will get Wallace!'

Anson caught Guy by the arm and held him tightly. 'You can't help him,' he answered harshly. They'd have you long before you could get to the top. Keep down, I tell you. The boy will be all right. Ten to one he's taken cover like ourselves.'

Half frantic as he was on Wallace's account, Guy had to own that Anson was right. The big plane was already round again.

Quite clearly, her crew knew exactly where Anson was hiding, and were manoeuvring to get their gun to bear on him.

But this was difficult. The rock behind which he and Guy were sheltering was part of the cliff itself, a sort of spur sticking out close by the path. They two were in a narrowish crack or crevice between it and the steep slope behind.

The worst of it was that the rock itself was small, so that there was barely room for the two to crouch side by side. It was distinctly on the cards that their enemies might get them by a quick burst fired sideways as they came down on the left handed glide.

'Watch out!' he cried sharply. 'The moment you hear their engine stop follow me round the rock. Remember your life depends on your quickness.'

The words were hardly out of his mouth before the roar of the twin engines ceased abruptly. Instantly Anson made a jump for the path side of the rock, and Guy was after him like a rabbit.

Only just in time. Next second a fresh storm of lead scourged the rock and the cliff face all round. A splinter stung Guy's leg through his stocking, another cut Anson's ear, making it bleed. Then the plane was down, nearly touching the little gray waves of the Bay.

The big biplane spun like a live thing, banking so steeply that her wings for an instant were almost at right angles with the sea. Guy got a glimpse of her crew. They were two in number, the pilot and the man at the gun. Fur-coated, hooded, and goggled as they were, they were both unmistakably German.

Only a glimpse. There was no time for more, for back she came, zooming up so close to the cliff face that the roar of her engines nearly deafened Guy.

Anson leaped back to his old position, Guy followed, and for a third time they were pelted with a deadly hail.

'Mucked it again!' cried Guy, as the plane went hurtling up out of sight over the rim of the cliff.

'But it can't last, Hallam,' answered Anson, between set teeth. 'It can't last. They're bound to have us sooner or later. If they can't get us this way, they'll land and come after us. I've stumbled on Germany's biggest secret. I'm the only Englishman who knows it, and they know that as well as I do. Cost what it may, they have to get me, and in a case like this their own lives count for nothing.'

Guy did not know either. What he did know was that, if he and Anson made any mistake and jumped to the wrong side of the rock, their lives would pay the penalty.

Then, before he could speak or even think again, there came a shock which made the very cliff tremble. The solid rock seemed to lift and fall again. On the heels of this followed a short, dull roar of sound—dull, yet with a curiously stunning effect.

Guy found himself flat on his back. He was half deaf and curiously confused. All he was conscious of was a sudden blast of wind that came sweeping off the sea with such force that sand and small pebbles flew inwards in showers, while the water itself was veined and streaked with foam.

'The neonite!' he shouted. 'Good for Wally! He's given the signal and set it off.'

'Plane!' retorted Guy. 'Plane be blowed! Do you think that any plane that ever flew could stick up in this sort of thing? I'll lay anything you like she's flat as a pancake. Come and see.'

CHAPTER II
VON FROMACH'S SECOND TRY

IN spite of his lameness, Guy beat Anson to the top of the cliff path. The first thing he saw was Wallace flat on his back on the turf.

'Wally!' he cried in dismay, as he ran towards him. 'Are you hurt? Did they hit you?'

'Hit me? The Huns, you mean? Not they. I don't believe the beggars ever saw me. But you—you and the other chap. Do you mean to say they never touched you?'

'The rock saved us, Wally. But they'd have got us next time if it hadn't been for the neonite. I suppose you touched it off?'

'You bet, I did. Gosh, didn't it make things hum? It was the wind of it bowled me over.

'Can't see her,' said Anson, coming up. 'Can't see a sign of her, so she's bound to be down. That whirlwind would have crashed any plane that ever flew.'

'Whirlwind!' cried Wally, whose eyes were sparkling with excitement. 'Whirlwind, you call it. That was dad's neonite. His new implosive.'

Anson stared. 'I don't know what the mischief you're talking about, youngster,' he answered. 'I never heard of an 'implosive.' But you can tell me later. What we've got to do now is to find that plane—and find her jolly quick. Because she's crashed, it don't follow that her crew are killed. And kindly remember they're armed and we are not.'

'Come on, then,' said Wallace eagerly. 'The chances are they are in one of those gullies. The gust came off the sea, so it must have carried them inland.'

'Steady! Go slow!' he said sharply. 'Just bear in mind that they may start potting at us any moment. We must scatter, and take all the cover we can find.'

The cliff top was covered with boulders and clumps of gorse. There was plenty of cover, and even Wallace was enough impressed by Anson's earnestness not to expose himself unduly. Keeping about thirty yards apart, the three worked steadily back from the edge of the cliff.

Guy's heart was beating more quickly than usual as he crawled through the gorse and heather. Things had been happening so quickly he had hardly had time to think. Now all of a sudden it struck him that the whole business was like some crazy dream. A quarter of an hour earlier, he and Wallace had been peacefully waiting to give the signal to the house to explode the neonite. Now they and Anson were tracking real Huns through the familiar Yorkshire heather.

All of a sudden he found himself on the edge of a gully. It was a deep wash cut in the black peaty soil, that ran curving down towards the sea. It was about forty feet wide and perhaps ten deep. He pulled up, and keeping his body well under cover peered cautiously over.

His heart gave a great jump. A little way up, the gully was blocked by an amazing tangle of tattered yellow wings mixed with broken spars, wire rigging, and all sorts of wreckage.

Next moment Anson was beside him, while Wallace came hurrying recklessly from behind.

'She's crashed all right,' said Anson rather grimly, as he stared at the mass of wreckage. 'Ten to one both the fellows are dead. Still, it's as well to be on the safe side. Follow me, but don't expose yourselves.'

Anson spoke as one accustomed to be obeyed, but Guy took no offence. He realised that the sailor knew exactly what he was about.

Presently Anson came to a stop behind a tall gorse bush which grew on the bank of the gully just above the wreck of the plane. For quite half a minute he lay perfectly still, watching the wreckage, while the others crouched close behind him, both more excited than they had ever been before in their lives.

At last he turned. 'Right O!' he said. 'They're either dead or stunned. Anyhow, there's no movement.' He turned to Wallace.

'Better stay where you are, youngster,' he continued kindly. 'A crash is always an ugly sight. It'll spoil your dinner and your dreams. You come on, Hallam.'

Anson slipped quietly over the edge of the gully and disappeared under one of the big upper planes, which lay like a roof across the rift in the ground. Guy, keen as mustard, followed close.

The plane had pancaked—that is, gone down flat, and in under the shadow of the wing was the fuselage. The wheels were wrenched off, the boat-shaped body itself was twisted out of shape, and in among the bent rods and torn fragments of the under planes Guy glimpsed two figures. One who lay clear was on his face in the bottom of the dyke. His body was doubled up, one leg twisted beneath him in an unnatural position. The other was still in the wrecked fuselage. He was leaning forward, with his head resting on his outstretched arms.

Guy's answer was to fling out both arms and push Anson violently aside. At the same time he himself dropped. Next instant the vicious crack of an automatic sent echoes rattling along the gully, the bullet ripping through the air exactly where Anson's body had been a second earlier.

Guy saw a large stone exactly under his hands. Without the smallest hesitation he seized it, straightened himself and flung it, all with the same movement.

There was a thud, a yell of pain, and the pistol barked once more, but harmlessly. Guy's stone had caught the treacherous German clean in the centre of the chest, doubling him up and knocking the wind out of him.

Before the fellow could recover or fire again, Guy was on him and, catching him by the throat with both hands, forced him back, till his head was jammed hard against the farther edge of the fuselage.

'Steady! Don't kill him,' came Anson's voice in his ear. 'Yes, I know he deserves it, but he'll be more useful alive. All right, I've got his gun. Hang on to him while I tie his hands.'

With sailor-like smartness, Anson secured the German's wrists with his own handkerchief.

'Now he's harmless,' he said. 'I say, Hallam,' he added with a grin, 'he'd never take a prize in a beauty show, would he?'

Anson was right. The Hun, scowling balefully up at them, was satanically ugly. He was quite short, but had the chest and shoulders of a giant, while his arms were as long as those of the original Black Dwarf. His head was bald as a coot's, and the smooth skull was shaped like a dome. He had a great hooked nose, a gash of a mouth, and small, deep-set, pale blue eyes.

Yet in spite of it all, he was a Prussian. You had only to glance at him to see it. Haughtiness, intolerance, and downright cruelty were written large all over him.

'Dead as mutton,' he pronounced. 'Now then, Hallam,' he went on briskly. 'Let's get this chap to your house and shut him up. We musn't run any chances. He's a jolly sight too valuable to lose.'

'Beggarly Englishman!' he stormed. 'You dare to speak to me in such a way! I am an officer and of noble birth. I demand to be treated with due respect.'

'You may be the Lord High Panjandrum himself,' retorted Anson. 'All I know about you is that you're a treacherous hound. You'd best make up your mind at once that there are not going to be any first-class carriages or motor-cars for you. So just put your best foot forward and come along.'

'I am the Baron von Fromach,' foamed the other, but Anson cut him short by dragging him out of his seat. Guy took him by the other arm, and between them they lugged him up the bank and started him in the direction of the house.

'Keep an eye on him, Hallam,' said Anson in Guy's ear. 'He comes from the Secret City, and it's worth anything you like to me if we can get him to own up. My story is so wild and woolly that I have my doubts as to whether any one is going to believe it unless I can get some backing.'

'The newest Hun dodge for smashing us, my son,' replied Anson gravely. 'I'll tell you all about it as soon as we reach the house. It'll be a big relief to get it off my chest. All the way across, as I was drifting in that infernal sausage, I was wondering what the mischief would happen if I was done in before I could get the news to England.'

Anson nodded. 'I've seen it,' he answered. 'But don't talk about it now. That beggar's ears are as keen as a hare's, and for all the sulky look of him, he's listening for all he's worth.

'Dead certain. I caught a flash of something in the sun. It's my belief some one is watching us through glasses.'

'A fellow who lives in an old farmhouse near here. Pretends to be on a fishing holiday,' Guy answered. 'But Wallace and I are pretty certain he's a spy. We've spotted him watching us more than once. He's after Mr Ingram's neonite.'

'Yes. It's the biggest thing yet. Well, you saw what it did. But I mustn't tell even you. Mr Ingram himself will do that.'

Anson nodded, and they trudged on in silence until they reached the house. Mr Ingram himself came to meet them. He was a man of fifty, with clean cut features and bright, luminous eyes. His hair was almost white, and his long delicate fingers were stained with chemicals.

'What's this? What has happened?' he asked quickly, as he stared first at the German, then at Anson.

'I am Sub-lieutenant Dick Anson, sir, late of H.M. Submarine Q2. This is my prisoner, a German named von Fromach. I will ask you first to find some secure lodging for him. After that I shall be glad to tell you my story.'

'The very place, dad!' exclaimed young Wallace eagerly. 'Here we are,' he continued, pointing to a small square stone building standing behind the slate-roofed laboratory.

Anson looked in. The place was stoutly built. It had no window, only a skylight, and the door was heavy and solid.

'I demand to be housed in proper quarters,' he said haughtily. 'This place is not fit for a dog.'

'I should be sorry to compare a decent dog with you,' said Anson dryly, and catching his man by the shoulders shoved him forcibly inside the magazine and slammed the door on him. Mr Ingram locked it and, putting the key in his pocket, led the way to the house.

'Dinner is just ready, Mr Anson,' he said courteously. 'I dare say you won't be sorry for some food.'

'You are right, sir,' he answered. 'When I tell you that the last meal I ate was aboard Q2 in the Baltic nearly two days ago, you can imagine whether I am hungry or not.'

CHAPTER III
DICK ANSON'S STORY

'CERTAINLY I will tell you all about neonite,' said Mr Ingram. 'But not yet. We must have your story first. It is not mere curiosity on our part. As you have said yourself, you are the only Englishman who knows this great secret of Germany, and it seems to me that the sooner you share your knowledge with some responsible person, the better for our country.'

Young Anson nodded. After a change of clothes, a bath, a shave, and a good meal, he looked very different from the worn, red-eyed, haggard person who had arrived at Claston a little more than an hour earlier. He was once more the spruce, keen-faced naval officer.

'You're right, Mr Ingram,' he answered. 'And I don't mind telling you that I shall be precious glad to get the story off my chest. If that beauty, von Fromach, had managed to pip me just now, I firmly believe we should have lost the war.

'Sounds a bit boastful,' he continued, with a smile, 'but when you have heard my yarn I rather fancy you will be inclined to agree with me.'

'Well, you know my name,' he said, 'and I think I told Hallam here that I'm a submarine man. I am, or was, second in command of one of our new class, Q2, and our job has been in the Baltic. I needn't bother you with the story of how we got in. It's enough to say that we succeeded where better men have failed, and that we had good luck all through.

'We strafed three big ships loaded with stuff from Scandinavia for Hun ports, and then as they were hot after us, we nipped up north a bit, in among those islands which lie between Sweden and Russia. They used to be Russian, but Fritz has bagged the best of them.

'One morning we found the temperature dropping in the most uncanny fashion. It wasn't the air only. It was the water as well. From a fine sunny morning as warm as an English May day, we ran, within a couple of hours, into a temperature that wasn't much above freezing point, and a dense fog.

'"It was August this morning," I told him. "Now we've either dropped three months in as many hours, or else we're running into ice. I've seen this sort of thing in the north Atlantic when there was a big berg floating down from the Arctic."

'"So have I," said Harman. "But there are no icebergs in the Baltic at any time. And the last of the floe ice melts in May."

'"I'll bet you there is ice, all the same," I declared. He got quite cross about it, and we were arguing pretty warmly when all of a sudden there was a crunch, and blessed if we hadn't run into a thin sheet of ice which seemed to cover the whole sea ahead.

'That finished the argument, but it only added to our perplexity. Mind you, it takes a lot of cold to freeze salt water, and even so far north as the Upper Baltic you don't get frost in August.

'Harman vowed he was going to investigate, so we backed out and began to coast around the edge of the ice. Soon we found that we were cruising in a circle, but the fog was still so thick that we had not the faintest idea what there was in the centre of the circle.

'We might never have known, only for a breeze that sprang up quite suddenly out of the east. It lifted the fog, and what should we see in the centre of the ice but a small island! It had low cliffs all around it, and from somewhere inside the rim of rocks smoke was rising.

'"Some of Fritz's devilry," I said, for by this time I had my glasses bearing. "There's a factory chimney up there in the middle of the island."

'He wouldn't have it at first, but when he had taken a good look through my glasses he was forced to confess that I was right.

'The next thing was what to do about it. We simply couldn't leave without making a shot to find out what was up. We decided to hang about until night, then dive under the ice and see if we couldn't make a landing somewhere.

'There wasn't much risk of being spotted. You see the ice out there in the middle of a warmish sea kept a regular steady fog going, and it was only when a strong puff of wind came along that we could even get a glimpse of the island.

'But I say, Mr Anson, what made the ice? I suppose it was some dodge of the Germans.'

'You bet it was,' replied Anson. 'We realised that at once, and I ought to have told you so. Somehow they have got on to the secret of producing intense cold. It's an idea that scientific people have been after for years, and I believe the thing has been done on a small scale by an Italian chemist. You can see for yourself what a tremendous pull it would give them both at sea and on land.'

'That is only too plain,' said Mr Ingram gravely. 'They could close any strait or harbour at will, while on land they could harden muddy ground so as to move artillery over it, or—if they can control the Cold Ray—they could actually freeze our forces in their trenches, and then advance over them at their leisure.'

'They can control the Ray all right,' said Anson, with a grim tightening of his lips. 'Listen and I'll tell you.

'When night came we dived. We had spotted a little patch of open water close under the cliffs, and that is what we made for. As a matter of fact, it didn't matter much about reaching it, for the ice was nowhere more than six inches thick, so that we could have broken it without much trouble.

'Harman, of course, had to stay by the ship, so he sent me off with a man called Harington, who was our coxswain. A big hefty fellow, yet quick on his feet as a cat.

'We went ashore in the dinghy, and landed on a ledge at the foot of the cliffs. There was no one about. I suppose they thought that the fog was protection enough. Anyhow, we found no one to interfere with us.

'The next thing was to climb the cliffs. They were not high, but they were most infernally steep, and in that cold the climb was anything but a joke. If it hadn't been for John Harington I should never have managed it.

'To cut a long story short, we did get to the top all right in the long run, and the two of us crept over the rim of the cliffs like a pair of scouts coming out of a front line trench into No Man's Land.

'The reason we were so jolly careful was that the fog had lifted a bit, and we had spotted a couple of sausage balloons against the night sky overhead. I suppose they always let them up when the fog is not as thick as usual.

'The ground along the cliff top was rough and rocky, which was just as well for us, for I tell you we needed all the cover we could find. If it had been dark climbing up the cliffs, it was light enough once we reached the summit. The whole interior of the island was a blaze of light.'

Anson paused a moment. His three listeners sat absolutely silent, waiting eagerly for him to continue.

'I must explain a bit,' he went on. 'This island—it's called Rosel Island, I believe, is a most curious shape. It's almost circular, and though there are these low cliffs all around, the centre is a great hollow, a sort of shallow basin which looks as if it ought to be full of water, but isn't. This hollow is about a mile across, and in the centre is a town. It's more than a town; it's a regular city, quite hidden from the sea by its rim of rocks, but as complete a place as you can possibly imagine, and wonderfully laid out.

'So far as I could see, the whole of the centre was one great factory. The chimney which we had seen from the sea rose from an immense power plant which was part of this factory. All around were workmen's houses, very neatly built. We could spot a large house, which is probably the Governor's, a school, a church, and other public buildings. From the size of the place there must be four or five thousand people in it—perhaps more.

'Near the chimney is a tower, a huge structure of steel girders, but not quite so high as the chimney, and on top of this is a thing which looks rather like an enormous photographic camera. This, I fancy, is the apparatus they use for producing the Cold Ray.

'I don't know how long we lay there, staring at the scene below. I remember noticing the people moving about in the streets, and all dressed as though they were bound for an Arctic expedition, and I can recall, as plainly as if I heard it now, the steady beat of machinery and the hum of dynamos. I could see, too, that opposite us was a break in the island wall, with a narrow opening into a small but deep harbour. Deep it must have been, for the three or four ships that lay there against the quay were all large ones.

'We were both so absolutely wonder-struck with all we saw that neither of us said a word, and it was not until I found that my teeth were chattering with the cold that I broke the silence.

'"We shall freeze if we stay here," I told him. "We had better shove on and get a closer view."

'Harington agreed. I could tell by his voice that he was as thunderstruck as I was myself. So he and I crawled on, taking all the cover we could find as we went.

'We didn't get far. Fritz don't take any chances. Next thing we knew, we were up against a barbed wire fence—seven strands, and probably electrified. I don't know whether he put it up to keep his own people in or other folk out. Anyhow, since we had no gloves or pliers, it put the hat on any further progress on our part. There was nothing for it but to go back and report. In a way I was not sorry, for it was getting colder all the time. That camera machine seemed to have swung round in our direction, and I tell you the temperature wasn't far off zero.

'So we turned, and were working back again to the edge of the cliff when Harington, who was a bit to the left of me, suddenly pulled up short. He didn't say a word, but pointed.

'A little to his left was a hole in the rock, the mouth of a pit some six feet square, and out of this rose a wire. It was of fine steel no thicker than a piano wire, and it rose straight up till lost in the darkness overhead. I could only see it by the faint gleam of light reflected upon it.

'What sort of infernal device this might be I had not the foggiest notion, but of course I had to see, so I crept up and peeped over.

'I tell you, I pulled back as quickly as a scared rabbit. I was looking right down upon the back of a large Hun who was squatting at the bottom of the pit. He was wrapped in a big sheepskin coat, and was sitting alongside a sort of windlass from the drum of which ran the wire I have spoken of.'

'Exactly. As I suspected then, and made certain of the fact later, the whole island is surrounded by a barrage consisting of small balloons sent up to a great height, and held by steel wire of great tensile strength. This barrage is an improvement on our own 'Apron' scheme, and completely protects the island from aeroplane attacks.'

'It is quite evident that the Germans are taking every precaution to guard this Secret City of theirs,' said John Ingram, frowning.

'That's what struck me,' replied young Anson. 'It means that they think a lot of whatever they have there, whether it's the Cold Ray or something even more diabolical.'

'No,' said Anson. 'I should dearly have liked to, but I had no right to take risks. I signalled to Harington, and we left the fellow and made off.

'If climbing the cliffs was bad, getting down was worse, and we were jolly glad when we reached the beach in safety. By this time the cold was something awful, and my one idea was to get back aboard Q2 and warm up a bit.

'The dinghy lay where we had left it, but the bit of open water was gone. It was all ice—thick ice, too. Rowing was out of the question.

'There was nothing for it but to walk across the ice and try to find the submarine. It was a dark night, we could not see ten yards ahead, and we had no notion whether the ice would bear. That walk was an absolute nightmare.

'But there was worse to come. When we reached the spot where we had left Q2, she was gone. There was not a sign of her.'

'I don't know. Even now, I have not the faintest notion. We had heard nothing, seen nothing. And you can bet your life Harman would never have deserted us. He is not that sort. Whether the Huns had spotted her and used some infernal dodge to destroy her, I can't say. I can't see what they could have done. It's true they had increased the cold, and it's just possible that Harman was forced to submerge to save Q2 from being frozen in.

'At any rate, our ship was gone, and Harington and I were left there alone on the ice, stiff with cold, and in about as tight a fix as I, for one, ever want to be in.

'There was nothing for it but to get back to land. My first idea was to tow the dinghy out over the ice and launch her and get away. But, as Harington reminded me, the outer edge of the ice sheet which was beyond the main power of the Cold Ray would not bear us. The only alternative seemed to be to wait under the cliffs till morning. But that wouldn't work either. They'd only spot us from their observation balloons, and then it would be the nearest wall and a firing party. Fritz was not likely to let any one live who had stumbled on his big secret.

'I said as much to Harington, and it was my mention of the sausage that put an idea into my head. It struck me that they would hardly keep the old thing up all night, and that by this time they had probably hauled her down. Why shouldn't we see if we could surprise her, steal her, and get away in her?'

'Of course, it was a crazy notion, but we were absolutely up against it, and even if we failed we could finish up in style. We both had automatics.

'Harington, stout fellow, jumped at it, so once more we climbed those chilly cliffs, and went groping along the top in that bitter, freezing fog.'

CHAPTER IV
AN UGLY SHOCK

'LUCKILY for me,' said Anson, 'I have a good bump of locality, and I had spotted exactly where the sausage was moored. The thing I was scared of was that she might be inside the barbed wire, but luck was good to us, and presently we spotted the outline of the big bag lying above a sort of rock emplacement, quite close to the edge of the cliff.

'We knew, of course, that there would be at least one sentry with her, but we hoped not more than one. Since it was out of the question to use our pistols, I picked up a useful chunk of rock, and Harington did the same.

'In our excitement we had forgotten for the moment all about the balloon barrage, and we had the narrowest sort of escape from blundering into one of the pits. Luckily for us, there was another shut-eye sentry in this place, and we got away without disturbing him. A few minutes later we were crouching side by side on the edge of the sausage emplacement.

'Fritz had done the job with his usual thoroughness. He had carved out a young quarry for the big balloon to lie in when the weather was stormy. You've seen the balloon itself, so you can judge how big the pit was. In the fog and the darkness we could not tell whether there was one man there or a dozen, and we had to make a circle of the whole place on hands and knees to find out.

'Suddenly Harington touched me on the arm and pointed. There was a little lean-to hut against the edge of the pit, and right beneath us. He didn't speak, but we both knew that this was where the guard must be sheltering.

'The worst of it was that we could not see inside, or tell how many men there were. There was nothing for it but to go down into the pit and chance it.

'I don't mind telling you that my heart was in my mouth as I slid over. Harington followed, and, big as he was, a mouse could not have made less noise.

'There were two men there—big, hulking chaps. One was dozing, but the other wide awake as you please. He looked a giant in his great sheepskin coat.

'It was no use waiting. I laid my stone down, pulled my pistol, and in two steps had the muzzle jammed against the side of his head.

'His mouth opened like a fish when it is pulled out of water, and his eyes goggled. Before he could recover himself or shout, or even move, Harington was behind him and had him by the throat. I saw he was safe, and so dropped instantly on the fellow who was asleep.

'Before he was awake I had my handkerchief in his mouth, and when he started to kick I simply choked him into submission.

'After that it was plain sailing. We tied the pair up like mummies, gagged and left them, then turned our attention to the sausage.

'Alone, I could not have managed it, but luckily Harington had had some experience of balloons, and he understood how to release her. Even so, it took some time, and we were in a deadly fright that some one might hear us.

'The moment we got the fastenings loose up she went like a rocket. Before we could get our breath we were clear of the fog cloud that shrouded the Secret City, and, high as we had risen, in air that was much warmer than it had been down within the radius of that fearful Cold Ray.

'I simply lay back and gasped with relief. We had been three hours on that abominable island, and it was like heaven to get away. Yet when I came to think of it, our position was pretty desperate.

'There we swung, a mile above the Baltic, without food or drink or even an overcoat between us. What was worse, we were absolutely at the mercy of the wind. As I have told you, the breeze was easterly, but who could tell when it would change? At this time of year the wind is generally westerly, and if it did turn and come from that quarter it would carry us either into Russia or Germany.

'Even if it remained easterly, it seemed to me that we had either to descend in Sweden or Norway, or else be carried out and dropped in the North Sea. Into the bargain, it seemed certain that before long the balloon would be missed and chased.

'However, it was not a bit of use worrying, so we simply sat tight. The breeze was very light, and it was a long time before we lost sight of the big white patch of fog and ice that we had left behind us.

'It faded away at last, and we drifted over a number of other islands. We could spot them by their lights set in queer patterns on the face of the dark sea.

'Dawn came at last, and found us both stiff with cold. Looking down, I saw mountains below, and told Harington that we must be over Norway.

'He suggested that we had better try to land, but the whole country below was a tangle of woods and rocks and lakes. I told him that it was hopeless. We should only smash up the balloon and ourselves, too.

'He agreed that this was pretty likely, but pointed out that there were two parachutes in the car, and that we might descend in those.

'I thought it over, and finally told him that he could try it if he liked, but that I fancied it would be best for one of us to stick to the balloon. My notion was that, once over the North Sea, I should be certain to spot some of our fleet, and could easily drop and be picked up. You understand, of course, that the one thing I was after was to get the news of my find to headquarters.

'"Very well, sir," he said, "I think I'll try my luck. If I get down safe I'll manage to get word through somehow. And, any way, it'll lighten the balloon a good bit, and give you a better chance of making it."

'The moment he was clear, the balloon shot up between three and four thousand feet. The sudden change of pressure made me so dizzy I could hardly see. Still, I did manage to watch Harington. The parachute had opened all right, but it looked to me as though the poor fellow was dropping straight into a large lake. I never saw him reach the ground. There was a gale blowing at the upper height, and it swept me and the balloon off at a tremendous pace.

'In less than an hour I was clear of the Norse coast and well out over the North Sea. There luck failed me. There was a haze below, a haze just thick enough to cut off my view of any vessels. But the wind, which at that height was north of east, carried me on briskly, and I had hopes. You see, I knew that, if it did not change again, I was bound to hit either the English or Scottish coasts.

'So I did. I was actually within sight of land when I saw that Hun plane after me. They had camouflaged her as British for obvious reasons.

'The rest of my story you know, but I should like to say this, Mr Ingram. I should never have had the chance to tell it if it hadn't been for Hallam here, who pulled me out of the sea, and your son who was smart enough to signal you to set off this extraordinary explosive of yours, just in the nick of time.'

He stopped and lay back in his chair. There was silence for some moments, then Mr Ingram spoke.

'All that I can say, Lieutenant Anson, is that it is a very fortunate thing for England that you have escaped to tell this story, and that the sooner the Admiralty have your news the better. And I will tell you another thing. In my opinion, the matter is so important that I think it should be put into writing at once.'

'It would be rather a good egg,' he answered. 'As a matter of fact, I did make a few notes in pencil on my way across. Here they are, and a rough sketch map. If you could get them copied out I'd sign them, and that would be some sort of safeguard.'

'I shall leave the notes in your charge, sir,' he said to Mr Ingram. 'And as for me, I must shove off to town as quickly as possible. What's the best way of getting there?'

'Just after four,' he said. 'There's a good train from Brocklesby Junction at eight thirty which goes right through.'

'Fourteen miles from here. Guy shall drive you over in the car. We have a two-seater, and they allow us just enough petrol for station work. There is no need to hurry. If you start at half-past seven you should have plenty of time.'

'In that case,' replied Anson, with a smile, 'I'm going to claim your promise, Mr Ingram. You said you would tell me about that neonite, you know.'

'I should jolly well think I did. That's just what makes me so keen. But I'll tell you this, if I hadn't seen it I'd never have believed that any explosive could do what that did. I mean, unless you used about ten tons of it.'

'You'll have to tell me now. If you don't, I shall have to say that I can't believe it.'

'Guy and Wallace will back me up,' said Mr Ingram. 'They were with me when I weighed it.'

'You needn't be so beastly formal,' he said quickly. 'Anson is good enough, if you don't mind. One doesn't stand on ceremony with a chap who has saved one's life.'

'Guy might be a lieutenant himself by this time, if the doctors would have passed him,' he said, in his quiet way. 'It's rough on him, for he's as keen as any man can be on the Navy. And as I dare say you have heard, he got that limp in getting another boy out of a burning building.'

'I hadn't heard,' replied Anson. 'And I agree that it's jolly rough on him. But never mind, Hallam, I'm sure you are doing just as good work for your country as if you were in a battleship.

'And now, Mr Ingram,' he continued, turning to the elder man, 'what about the neonite?'

'There is not really much to tell you,' answered the other. 'Years ago I had the idea that, by combining nitrates with one of the rarer elements I could produce an entirely new form of explosive. For the rest, it was merely a matter of experiment. That I have had some success seems to be proved by to-day's achievement.'

'I should rather think you had,' declared Anson with enthusiasm. 'I've had a good bit to do with explosives myself, but the effect of that was absolutely new to me.

What struck me was the amazing displacement of air. Why, a regular gale came in from the sea.'

'That's the secret. The actual result of the firing of neonite is to cause a complete vacuum over the whole area of the explosion. For the moment the ordinary pressure of the atmosphere, which, as you know, amounts to fifteen pounds to the square inch, is absolutely removed. You realise what must happen.'

'I should rather think I did. Why every cell in every living thing within that area must burst open. Good Heavens, what a ghastly business!'

'Ghastly is the word for it, my boy,' replied Mr Ingram gravely. 'It means that all animal and vegetable life within the pressure area is instantly and utterly destroyed. I reckon that if a fifteen pound shell full of neonite were exploded in the middle of Trafalgar Square, all life would cease within that space. What is more, every house of which the doors and windows were closed would be burst open and destroyed.'

'It's the most terrible invention I ever heard of,' he said slowly. 'A few score shells would destroy the largest city in the world.' He paused and considered for a few moments. Then his face brightened and his blue eyes gleamed.

'But I tell you this, Mr Ingram. Any nation possessing such a secret could win the war single-handed.'

'That I believe to be true,' replied the inventor. 'And I will confess to you that it is only with the hope of destroying the brutal force of Germany that I am going on with neonite. Without that hope, nothing would induce me to make my secret public.'

'Perfectly! It can only be fired by a special fuse also of my own invention. You can pound it with a hammer or burn it in a fire with perfect safety.'

'You can. But, as a matter of fact, I have devised a new gun by means of which I can throw large shells to practically any desired distance, and that without any sound that could be heard two hundred yards away.'

'It is really very simple,' went on Mr Ingram, smiling. 'The gun I speak of is on the electric principle. Have you ever heard of the Bachellier electric railway?'

'Yes. Bachellier used the repulsion and attraction of certain metals, didn't he? When his car started it rose clear of the rails and ran between guides.'

'That was it. Well, my gun is on similar lines. It is a tube of any desired length made of spools of soft iron and aluminium, and wound with copper wire. No rifling is necessary, for the projectile itself is winged. I have already built a small gun, and I reckon that if I constructed one 300 feet in length and used about 300 horse power, I could get a muzzle velocity of nearly five miles a second.'

'And I'll go and get the car ready,' said Guy. 'Oh, and what about von Fromach? I suppose the fellow ought to have something to eat.'

'Yes, we must keep him alive until we can hand him over to the military authorities,' said Mr Ingram. 'He and the remains of his plane are the chief proofs we have of the truth of Anson's story. But don't go alone, Guy. The man is dangerous, and it won't do for any of us to enter his prison without a second person.'

'Very well, sir,' agreed Guy. 'Then I'll get the car ready and wait until you come back.'

Guy took extra pains with the car. So far as he was concerned, he meant to make certain that all would go well with Anson's journey up to London. Young as he was, he realised as clearly as Mr Ingram himself the enormous importance of Anson's discovery. He filled the petrol tank, greased wheels and bearings, and ran the engine to make sure it would start easily.

When he came out of the garage he found that the weather was changing. Gray fog clouds capped the high moors inland, and a thin drizzle had begun to fall.

'Going to be bad for our drive to Brocklesby,' he said, frowning a little. 'We must start early. It won't do to risk fast travelling on those hills in fog.'

As he reached the house Mr Ingram and Wallace came out. Wallace was carrying a tray with some food on it.

'Grub for the Hun,' he explained to Guy. 'If I had my way he'd get bread and water, but dad won't have reprisals, and he's going to get cold meat and cheese.'

'It's more than I should have got if they'd caught me on Rosel Island,' said Anson dryly, as he came out behind the others. 'Just about time for us to start, isn't it, Hallam?'

'It would not be a bad idea. To tell truth, I was thinking of it myself. Your testimony would be useful at the Admiralty, Guy. Can you pack in ten minutes?'

He rushed to his room, seized a bag, and was flinging things into it when he heard a shout outside.

It was Wallace's voice, and the dismay in it startled Guy. Dropping everything, he ran out.

Wallace met him. Wallace, white-faced and more excited than Guy had ever seen him.

'How can he possibly have escaped?' demanded Guy. 'The door was locked. There was no way out.'

'The skylight's open. Some one must have helped him.' Guy stared a moment at the other. Then his lips set, and his whole face hardened.

CHAPTER V
WAYLAID!

'AREN'T you going a bit fast, Hallam?' asked Anson, as he stared through the screen at the low banks looming mistily through the fog, on either side of the road.

'I've got to,' Guy answered. 'I've got to crack on if we are to catch that train. We were a good quarter of an hour late in starting.'

'Through that swine of a German,' said Anson angrily. 'D'ye know, Hallam, I'm half inclined to think that we should have done better to put off our trip until the morning. I don't like the idea of Mr Ingram and his son being left alone to hunt for that ugly brute.'

'I told Mr Ingram so,' replied Guy. 'But he wouldn't hear of it. He vowed that he and Wallace could manage all right, and told me that the great thing was to get you up to town as quickly as possible.'

'A few hours would not have made much difference one way or another,' he said. 'As it is, I'll bet we shall be kept hanging about for hours on the Admiralty doorstep. And then some red-tape-tied big wig will hum and haw, and want a certificate from an inspector in lunacy before he'll believe a word I say.'

Guy did not answer. All his attention was taken up with handling the car. If there is one form of driving more dangerous and difficult than another, it is to keep a car going in a fog on an open road. Where there are hedges or trees the driver has some sort of guide. Here on the open moor there were only the low banks on either side, and sometimes not even these.

The lamps did not help a bit. In fact, they only made things worse by flinging a white glare on the fog in front.

For some minutes they had been coasting at a moderate pace down a long hill. Now Guy took off both brakes, and pressed down the accelerator.

'It's all right,' he said to Anson. 'We're at the bottom now. I may just as well gain all I can by rushing this next hill.'

The words were hardly out of his mouth before there was a crack like a rifle shot, and the light car swerved violently.

Guy cut off gas, and flung on both brakes. Before he could pull up there was a second report as loud as the first. The car stopped abruptly.

'Both front tyres!' groaned Guy. 'What wicked luck! Must be some monkey business, for both covers were nearly new.'

'Don't stop her,' said Anson sharply. 'Shove her along, even if you have to run on the rims.'

As he did so something swished through the air and came down with a thud across the back of the seat, on the very spot where Anson had been sitting the instant before.

'Look out, Hallam!' came a quick cry from the young lieutenant, and Guy leaped to his feet just in time to see a figure, dim in the mist and twilight, leaping on to the back of the car.

In spite of his lame leg, Guy was active as a cat. And he had his wits about him. He did not hesitate for even a fraction of a second. Whirling round, he jumped on the seat, and flung himself straight at the attacker.

The latter had put all his force into the blow with which he had meant to out Anson. He had not time to straighten himself before Guy was on him. Guy caught him round the neck with both arms, and threw his whole weight forward.

Caught off his balance, the man staggered backwards and, with Guy on top of him, went clean over into the road.

Falling on top of him, Guy was not hurt, but the force of the fall knocked the wind out of the other, and it was a moment or two before he could recover.

From close by came the sound of heavy breathing and the dull thud of blows. Guy realised that Anson was being attacked, and scrambled up as quickly as he could.

As he did so the man beneath him caught at his foot and nearly pulled him down. Guy turned on him desperately, and drove at his head with his clenched fist.

There was a shriek of pain, and the fellow writhed a moment, then flattened out and lay still.

Guy jumped clear. The fog was thicker than ever, and the dusk was closing in fast. All that Guy could see was dim forms rolling over and over on the grass at the side of the road.

As he came up, Guy saw that there were two men on top of Anson. A third stood by, with something in his hand that looked like a short, thick stick. It came to Guy in a flash that it was a sand-bag such as the first man had used. The fellow was waiting for a chance to bring it down on Anson's head.

But Anson, judging by the way in which the struggling figures on the ground were heaving to and fro, and the savage but low-voiced curses that came hissing from his assailants lips, was putting up a pretty stiff fight.

As quickly as he had tackled number one, Guy went for the man with the sand-bag. But this chap saw him coming, and hit out for all he was worth.

Guy flung up his left arm to protect his head, and the sand-bag struck him over the shoulder, numbing the muscles so that the arm dropped useless by his side.

But the blow did not check him, and his right fist met his opponent's jaw with a force that knocked the fellow clean off his legs, and stretched him gasping and clucking on the wet turf.

Guy wasted no more time on him, but jumped into the fray, and, stooping, got hold of one of Anson's assailants by the collar with his sound arm.

Putting forth all his strength—and Guy had more than many a grown man—he jerked him backwards with all his might, and tore him clear off Anson.

With a snarl of rage the burly brute was scrambling to his feet, but Guy, realising that with his damaged arm he would not stand a dog's chance against him, threw scruples to the winds, and kicked him on the shin with all his force.

The man gave a howl of agony, and staggering back fell over his companion, whom Guy had floored already, and went crashing into the ditch beyond.

Once more Guy turned to Anson's help, but this time it was not needed. Left with only one man to tackle, Anson was quite equal to the occasion. Guy saw him kneeling on the spy's chest and throttling the fellow in a most satisfactory manner.

The man was kicking and struggling like a newly-landed fish, and his struggles were so tremendous that Anson was flung up and down like a pea on a drum. But he hung on like a bull dog, and in a very few seconds Guy heard a nasty choking rattle, and saw Anson's opponent go limp as a wet bootlace.

'Good for you, Hallam!' he said. 'Jove, you were only just in time. The two were more than I could manage. Where are the others?'

'All outed more or less. I'm not so sure about the last one. He's in the ditch there.'

'We must make sure of him,' said Anson curtly. 'If he gets away he may bring help. Got anything to tackle him with.

'Nothing much,' said Guy. 'One of them got me a wipe with a sand-bag. I can't use my left arm yet, but I expect it will be all right in a few minutes.'

'Wait, we must see about that fourth man before we do anything else,' returned Guy. 'Where's your pistol?'

'One of those swine got a knife into me somewhere,' Anson answered. 'Right shoulder, I think. But it's nothing to make a song about. I—'

His voice had gone oddly hoarse. He staggered. Guy had just time to fling his sound arm around him and save him from falling.

'I—I'm all right,' muttered Anson, making a violent attempt to pull himself round. Then he collapsed completely, and lay a dead weight in Guy's grasp.

Guy laid him down, and with his sound hand opened Anson's jacket. Waistcoat and shirt both were wet and warm. It was a deep cut, and was bleeding fast.

Taking out a handkerchief, Guy set to tear it into strips to bandage the wound. He found that this was impossible. His left arm was still completely useless, and he could do nothing with one hand.

He groaned with despair. Guy was not a person to be easily discouraged, but never in his life had he felt so completely helpless. The car was useless, and even if it had not been disabled, he could not drive it with one hand. He was alone in the dark and the fog, with Anson apparently bleeding to death before his eyes, and there was nothing he could do to help him.

To make matters worse, one, if not two, of their late opponents were not yet completely outed, and if any fresh attack were made he could do nothing to hold it up.

Stay, though! There was Anson's pistol. Guy managed to lift the young sailor slightly and get out his automatic.

As he did so he distinctly heard a rustle in the long grass close by. He raised the pistol and pointed it in the direction from which the sound had come.

Again the rustle. Guy stood absolutely motionless. The suspense was horrible. He did not know whether to fire or not.

It seemed to him that some one was crawling slowly up the ditch, but strain his eyes as he might, he could get no glimpse of him. He could hardly breathe. If Guy had been alone, he would have made a rush and chanced it. But he had Anson to think of, and Anson's life, he knew, was far more valuable than his own. Anson was the only man in England who knew of the existence of the Secret City, and it was up to him to see that Anson lived to tell his story.

It was very nearly dark now. But not too dark to see the tall marsh grass that rose like a screen above the ditch. And it was moving. It was surely moving. Guy strained his eyes until they ached. He felt just then that he would have given anything to know whether it really was that fourth man crawling nearer, and whether he had a pistol or not. It struck him as strange that the gang had not used fire-arms, but it was quite likely that they had purposely refrained from doing so. The spot where the car had been held up was on the edge of the moor, and Guy knew there were farm-houses not far away. Unfortunately, he had no idea in which direction.

He glanced down again at Anson. The young sailor lay terribly still. For all Guy knew, he might be dead already, and the idea drove him nearly frantic.

The strain was almost beyond endurance, and Guy was beginning to feel perfectly sick with suspense when suddenly a new sound came dully through the rolling billows of fog.

Guy stiffened, and stood listening breathlessly. Surely it was the distant hum of a motor engine. A moment later, and he was certain that a car was coming from the opposite direction.

His finger tightened on the trigger. Then he paused again. It struck him that this might be the gang's own car bringing them help.

Once more the grass rustled. Guy saw, or thought he saw, something dark behind the waving screen. He waited no longer, but fired straight at it.

With the wicked crack of the automatic came a yell of agony. There was a heavy fall, then silence.

Next moment Guy heard the deep hum slacken. The car was stopping. But it was so near now that he could see the glow of the lamps through the fog. Throwing prudence to the winds, he dashed out into the road and shouted at the top of his voice.

There was a low-voiced exclamation of surprise, then steps rang clear and sharp on the hard road, and a man came quickly forward.

There was a click, and a flood of white light from a powerful electric torch cut the fog and fell full upon Guy and Anson, and upon the two of the gang who lay insensible on the trampled turf.

'Gad, it's true!' said the man with the torch. 'What luck! What wonderful luck!'

'My friend—Lieutenant Anson!' he said. 'Quick! Help him. He is bleeding to death.'

His voice went suddenly hoarse and weak. He staggered. But before he could fall a strong arm saved him, and laid him gently on the grass.

'All right, my lad,' said the stranger. 'Lie still a minute. I'll see to your friend.'

CHAPTER VI
THE 'DUG-OUT'

GUY did not actually faint, but for a moment or two he must have been pretty nearly unconscious, for the next thing he was aware of was the sharp taste of spirit in his mouth.

'Swallow it down,' said the voice, and there was a tone in it which comforted Guy mightily. 'It'll do you good. You look as if you had had a pretty rough passage. Is that arm of yours broken?'

'Nothing serious. He has lost a lot of blood, but I have stopped it, and he will be all right. Now sit up and let me look at your arm.'

Guy sat up readily. He was still a little dizzy, but the faintness was passing away. While the stranger examined his arm, Guy examined him. He seemed to be about forty, a square-shouldered, deep-chested, well-built man who looked as if he might have been a retired cavalry officer. He had as keen a pair of eyes as Guy had ever seen in a human face, but apart from these eyes, which were of a curiously steely-blue colour, there was nothing remarkable about him.

'Bones are all right. That's a good job. But you are badly bruised, my boy, and those bruises will lame you for a month if they are not attended to pretty soon. Where do you belong?'

'No, his assistant, sir. My name is Hallam. But we can't go back. We are on our way to London.'

'That leaves in five minutes, Hallam. So I am afraid it is out of the question. Besides, you are neither of you fit to travel! Anson, especially, should be in bed for some days. The best course will be for me to drive you back to Claston. But, first, I must see about these cattle.' He pointed contemptuously to the men on the ground.

'There's a third in the ditch, sir,' said Guy. 'I shot him just as you came up. I had to. I thought he might kill Anson. And Anson—'

Guy cut himself short abruptly. He felt he had been on the verge of saying more than was wise.

'Quite right. I see there is more in this than meets the eye. I shan't ask for any confidences until you feel inclined to give them. Meantime, sit tight until I make these animals fast. I can leave my chauffeur to guard them and your car, and come back for them after I have taken you home.

He gave a call, and a second man appeared—a man in chauffeur's uniform; yet to Guy he looked much more like a sailor than anything else.

'Garland, I want you to take charge of these prisoners while I drive these gentlemen back to Claston. Take the flask, my torch, and the first-aid case. Keep the swine alive if you can. If I am not mistaken, they are the very gang we were after. I should like to be sure that they are properly hung later on.'

Vassall's voice rang suddenly grim, and Guy wondered greatly who he was, yet felt certain that he was to be trusted.

Between them, Mr Vassall and Garland lifted Anson into the tonneau, and made him comfortable. Guy got in beside Vassall, and the car, which was a big and powerful one, swept away. Guy noticed with interest that she had some sort of fog-piercing lenses on her headlights. Even in the thickest of the smother her driver did not drop to less than twenty miles an hour.

Vassall kept his word, and did not ask a single question on the way back. Guy, who instinctively felt that he could thoroughly trust this new acquaintance, longed to tell him all about the extraordinary happenings of the day, yet felt that he must not do so without knowing definitely who he was.

As for Anson, he was in no condition to talk at all. Although he had come back to his senses, he was almost too weak to move, and lay quite still in the tonneau where he had been placed.

Within less than fifteen minutes the lights of the lonely house at Claston glowed dimly through the fog, and Vassall drew up at the door.

To Guy's surprise, Mr Ingram himself came out. There was dismay on his face when he saw Guy and Anson.

'We were attacked on the road, Mr Ingram. This gentleman, Mr Vassall, came to our rescue and brought us back. There's not much the matter with either of us, only Anson is not fit to travel for a bit.'

'Who is Cratch?' cut in Vassall sharply. 'No—wait! I have no business to ask questions until I have given you some proof of my identity. Let us get these two youngsters to bed, and then I should like a few words with you, Mr Ingram.'

'No. I can assure you that the wound is nothing,' replied Vassall. 'I know something of surgery, and you can rely upon what I say. The weakness is simply loss of blood. And, if it's any comfort to you, I can tell you that these boys have outed three of this pernicious gang of spies and traitors.'

'I am delighted to hear it,' said Mr Ingram warmly. 'Now help me upstairs, if you will, with Anson. Afterwards I shall be glad to have a talk.'

They put Anson to bed, and Vassall dressed the ugly cut on his chest with as much skill as any doctor could have shown. Then he made Guy strip, and bathed his damaged shoulder with very hot water. By this time the whole upper part of Guy's arm was badly discoloured and swollen. Vassall put on a dressing and ordered Guy to bed.

Later on Hannah, the housekeeper, brought Guy some supper, and Guy begged her to ask Mr Ingram to come and see him before he went to bed.

'I'll tell him, sir,' replied Hannah, 'but he won't be coming yet a while. He and that gentleman are still talking down below.'

It was late before Mr Ingram did come up, but Guy was still awake, waiting eagerly to hear the news.

The moment he set eyes upon Mr Ingram's face he saw that the news was good. The inventor looked much less anxious than he had a couple of hours earlier.

'We are in luck, Guy,' he said. 'Mr Vassall is a Secret Service man, and is, it seems, on the track of this very gang that held you up to-night. He is extremely pleased with you for securing three prisoners for him.'

'That is a bad business,' said Mr Ingram, frowning. 'We had to give up the search because of the fog. But Mr Vassall is taking the whole affair in hand, and he is a great deal more likely than we to run down this ruffian.'

'He has to get proof first, Guy,' replied the other. 'But once he has that, I don't think that Cratch will trouble us much more.'

'Good! I do hope he gets him. And now the only thing I still want to ask you about is our trip to town.'

'As for that, you will have to wait until Anson can travel. But since Mr Vassall feels sure that he will be fit to go in three days, the delay will not be a long one. Now, good-night, Guy. You must get some sleep.'

'You have done very well to-day, Guy,' he said. 'I am very pleased with you. So, too, is Mr Vassall.'

Before Guy could even thank him, he was gone, and Guy, feeling that, even if he was lame, it was still very well worth while to be alive, turned over and went sound asleep.

Next day, as Vassall had prophesied, Guy was very stiff and sore. But being hard as nails, and always in tip-top condition, he very soon mended. On the second day he was about as usual, and found Anson, too, almost himself again.

Anson was dead keen to hear what had happened about Cratch and von Fromach, but Guy could give him no news, except that Cratch had vanished. He was no longer at the farm-house, and no one had heard anything of him. Nor was there any news of von Fromach.

Next morning came a letter from Vassall. It had no address, but was just a slip to say that he had no tidings of von Fromach, and warning them all at Claston not to breathe a word of what had happened.

It was on Friday that Anson had landed. On the following Wednesday he was well enough to travel. At least he vowed he was, and declared that he simply must take his story to the Admiralty.

This time he and Guy took no chances, but drove to Brocklesby in broad daylight, and caught an early train.

'What's the matter, Dick?' asked Gay. In the past few days the two had become great friends.

'I've told you, Guy. These old fogeys at the Admiralty are not going to believe me. They'll smile and talk about the weather, and presently they'll ask if I've had shell-shock, and hand me over to a medical board. Bless your innocent soul, I know 'em.

'There's only one chance,' he went on very earnestly. 'That is, if Admiral Dayle is in town. He was my old skipper in the "Invulnerable." He'd believe me.'

'Let's pray he is there then,' said Guy. To him it was hard to believe what Anson said, and he fancied that it was largely a case of nerves.

He was to learn better before he was much older. Next morning, when they arrived at the Admiralty, Anson asked at once for Admiral Sir Rupert Dayle. After some delay, he was told that Admiral Dayle was not in London. No, they could not say where he was, except that he had left town some days earlier, and would not be back for a week. Would Lieutenant Anson like to see Captain Karslake?

'Haven't a notion who he is,' whispered Anson to Guy. 'Still, I suppose he's better than no one.'

The messenger led on. They were taken up many stairs, and through a maze of passages, and left to cool their heels for a long twenty minutes in an ante-room.

At last another messenger appeared—a girl, this time—and told them that Captain Karslake was at liberty.

They were ushered into a large, airy room, but the moment Guy's eyes fell upon the Captain his heart sank. Captain Karslake was obviously a dug-out, a relic of the old Navy, which, even up to the beginning of the twentieth century, carried pikes to repel boarders.

A fine-looking old man in his way, but he looked at least seventy years old, and he had a long, stubborn upper lip and small gray eyes, under a thick thatch of snow-white brows.

'And you come with a confidential report?' continued the Captain, in a dry, harsh voice. 'What is this civilian doing in your company?'

'For two reasons, sir. First, that I do not know whether Commander Harman is dead or alive; and, secondly, because the matter is of such enormous importance.'

Captain Karslake grunted. The sound seemed to imply that he did not in the least agree with Anson.

There is nothing more difficult than to tell a story to a thoroughly unsympathetic audience. Even Guy felt that Dick was not making a success of it. It struck him most forcibly that the whole thing sounded like a fairy tale.

'Yes, sir. It is one of the outer islands of the Aland Archipelago. It is charted as Rosel. I have a note here of its exact position.'

'And this is where H.M. Submarine Q2 ran into the artificial ice sheet you speak of?'

'And you went ashore, I understand, and when you returned could not find your ship?'

'That is the case, sir. I have not the least idea what happened to her. But I am very sure that Commander Harman would not have left Harington and myself in the lurch unless he had been compelled to do so.'

'No. Quite so,' said Captain Karslake, rising. 'Mr Anson, will you return into the ante-room while I put a few questions to your friend here.'

'You assert, Mr Hallam, that on the 21st last you saw Lieutenant Anson descend at Claston from a captive balloon.'

'He did, sir, but quite close to land. I pulled him out, and we were then attacked by a large German sea-plane, which was afterwards brought down.'

'Yes, yes. Now tell me, did Lieutenant Anson seem to you to be in a normal condition when you rescued him?'

'He was half frozen and starved, sir, but otherwise all right,' replied Guy, in some surprise.

'Certainly I did, sir,' answered Guy, with a touch of indignation. 'The fact that the German sea-plane had followed and attacked him was pretty good proof, if any were needed.'

'I do not cast any doubt upon what you allege, Mr Hallam,' he said quietly. 'I am content to accept your statement that Lieutenant Anson did descend from a captive balloon in a parachute, and was attacked by a sea-plane.'

'Yet you do not believe the rest of his story?' said Guy, with a boldness that surprised himself.

'I do not,' answered the Captain curtly. 'I do not, and I will tell you why. It is perfectly true that Q2 is a total loss. Yet she was not wrecked in the Baltic. Life-belts and other portions of her were picked up yesterday in the North Sea.'

CHAPTER VII
THE FIRST SHELL

'I TOLD you, Guy,' said Dick Anson, and his young face was set and stern. 'I told you how it would be.'

The two were sitting in a quiet corner of the smoking room in their hotel on the evening after their interview with Captain Karslake.

'It's lucky for me that they have not shoved me into a hospital or a lunatic asylum,' went on Dick grimly.

'Appointed me to another ship. I'm to join her at Portsmouth to-morrow. She's a submarine of the Q class, and her skipper is Jack Mainwaring. I never met him, but I believe he is a good chap.'

'Go home, old chap. Go straight back and tell Mr Ingram all about it. Then see if you can get hold of Vassall. It seems to me that he is our only hope. You see, he believed me, and some of these Secret Service men can do a lot. Anyhow, I am certain that he realised what an awful danger this Secret City may prove to us all, and perhaps he can get the ear of some one who will move in the matter. At any rate, that is our only chance.'

'Right you are, Dick,' he said very earnestly. 'I'll do all I can. Luckily, we have your notes. I typed them all out, and they have your signature.'

'What bothers me,' he continued presently, 'is what old Karslake told me about the wreckage of Q2. How could it possibly have been found in the North Sea?'

'I've been thinking about that,' said Dick. 'There are two explanations. Harman may have been attacked and forced to clear out. In that case it would have been his duty to get back as quickly as possible, and carry the news to the Grand Fleet or the Admiralty. The Kattegat is full of mines. He may have hit one, and been destroyed.'

'The other solution is this, and it's the one I am inclined to believe in. The Huns may have collared Q2 at Rosel. For all we know, they had some device by which they took her, crew and all. Since their one idea is to keep the secret, what would they be likely to do, Guy?'

'I see. They would have taken anything they could out of her, and set it afloat in the North Sea. They'd have realised that, if it was picked up, it would queer your story at once.'

'Now you've got to remember this,' went on Anson earnestly. 'Fritz is very thorough in his methods. Von Fromach knows everything, and by this time the chances are that Berlin knows it too. They are aware that I am still alive, and that so long as I live there is danger. So, naturally, they will do all they know to wipe me out.'

'Just so. And it was just luck they didn't succeed. If I had had that sand-bag across my skull I should never have opened my lips again.'

'Then perhaps it is just as well that you will be at sea,' said Guy quickly. 'You'll be safer in a submarine than anywhere else.'

'There's something in that, but what I was going to say is this. You are in just as much danger as I am, Guy, and so, I think, are the Ingrams.'

Guy flushed a little. His eyes brightened. It did him good to feel that he was of some importance.

'That's all very well. Guy. But kindly remember that it's up to you to look after yourself and the Ingrams as well. It's your duty. D'ye see?'

'Right you are,' said Guy briskly. 'I'll keep my eyes peeled. And don't you worry your old head, Dick. Somehow or other we'll get this thing through. Like you, I believe that Vassall is our trump card. I'll try to see him as soon as I get back. Now, let's turn in. I've got to start at an unholy hour in the morning.'

Next morning the two parted, and Guy caught an early train for King's Cross. After a long journey in a very crowded carriage, he reached the junction and found Wallace waiting for him with the car.

'Not a thing, Guy,' Wallace answered. 'Cratch and von Fromach have simply vanished. Dad had a line from Mr Vassall, but he seems to think that both of 'em have managed to get out of the country. Pretty sickening, isn't it?'

'He didn't say so, so I suppose they're mum. Anyhow, it isn't likely that they know anything about their chiefs. Now tell me what you and Anson did in town.'

'Not a blamed thing that was of any use,' Guy answered, and went on to tell Wallace what had happened.

The evening was very clear and fine, and they got back to Claston quite comfortably, and found supper ready and waiting. Over the meal Guy told his story all over again, and Mr Ingram listened in silence.

'I am not surprised,' he said, when Guy had finished. 'It is the old story all over again. Even now, after more than four years of war, people here do not begin to realise the remorseless driving power of our enemies. We have paid for our foolishness already, and we shall pay again.

'Well, Guy,' he went on. 'You had better keep in mind what Anson said. You and I, as well as he, are in constant danger, and while there is no need to worry about that, it will be just as well to take every precaution.'

Guy, reaching his room, went to the window, opened it wide, and put his head out. It was a glorious night, with the moon shining brightly on leagues of heather-clad moorland. The air was fresh and clear, wonderfully different from the stuffy atmosphere of London. He stood, taking deep breaths of it, and feeling glad that he was alive.

Suddenly the silence was broken by a deep and heavy boom. The windows rattled, and Guy stood breathless, wondering what on earth had happened.

Next instant the boom was followed by a crash, a crash so loud and so close at hand that the whole house shook.

Guy waited no longer, but dashed out of the room. As he reached the landing Mr Ingram met him.

'Yes, a U-boat—out in the bay. I saw the flash from my window, which faces the sea. Call Wallace and get out of the house as quickly as possible. Take shelter under the sunk fence and wait for me.'

Guy did not hesitate. He ran to Wallace's room, but Wallace, like the rest, was already out. The two, together with stout Hannah, the housekeeper, hurried to the garden.

Before they reached it the gun crashed out again, and a shell came whistling over.

There was a shattering crash, and the air was filled with flying fragments of masonry. As the smoke cleared they saw that the old magazine, the very place where von Fromach had been imprisoned, was lying in a mass of ruins.

They got her into safety just as the third shell landed in the centre of their potato patch, sending black loam and Early Rose potatoes in every direction.

'Naturally. I'm not likely ever to get a better chance,' replied Mr Ingram dryly. 'Let's only hope they don't hit the shed or workshop before I can get at them.'

'That's a bit of luck,' said Mr Ingram, with a grim smile. 'Saved us a big glazier's bill.'

Close by the cliff edge was a long, low building with a roof of galvanised iron, painted a dull green colour. Into this Mr Ingram darted, with Guy close behind him. Inside was a pit, and lying on mountings within the pit, an object somewhat resembling a large telescope, only that it was the same diameter for the whole of its length.

The muzzle of this strange-looking affair protruded from an opening at the seaward end of the building.

'Get down into the pit and be ready to elevate,' ordered Mr Ingram, as he ran to a switch. 'Thanks be, the accumulators are all charged. Even so, I doubt if there is power for more than two shots.'

'One will do the trick if we can get anywhere near her,' said Guy. 'Ah, there's the flash again.'

Through the still night air the gun boomed again, and the shell came screaming on its deadly errand. This time it struck the face of the cliff almost exactly beneath the end of the shed, and the shock of the explosion nearly flung Guy off his feet.

'Quick!' breathed Mr Ingram. 'They know their target now. If they hit the shed before we can fire, gun and all are done for. And I can never afford to build another.'

Guy was already in the pit. He had his hand on a screw lever, and was waiting while Mr Ingram inserted a shell into the breech of the gun. The breech was as open as the muzzle. There was nothing to do but to place the shell in position, a small catch holding it so that it could not slip back while the gun was being trained.

'Up with her!' ordered the inventor, and as Guy spun the screw the muzzle of the long tube began to lift.

'There, that will do. Swing her a trifle—to the left. Ah, there's the flash again.'

The U-boat was loading and firing at top speed. She knew how short her shrift would be if any British destroyer or cruiser heard the racket and got after her. Her one idea was to strafe the Claston works before she was caught.

This shell, like the last, struck the face of the cliff, beneath the shed, but so close that the mass of rock which it dislodged was spattered all over the shed itself, stones ringing on the roof like shrapnel.

'She'll get us with the next,' said Mr Ingram between set teeth. 'All right, Guy. I think she'll do. Stand clear.'

Guy leaped up out of the pit, and as he did so Mr Ingram pulled over a switch. There was a click followed by a slight hissing sound, which rose at once to a shrieking whistle, as the shell, doubling its speed with every segment through which it travelled, raced towards the muzzle, then out into the night beyond.

Guy held his breath as he waited. It was only a matter of a very few seconds, yet it seemed an age before the explosion.

It came with a sharp burst of white flame, then a thud of sound, as different as possible from the sharp smack of the high explosive in the Hun shells.

'Got him!' roared Ingram. For once, the great inventor's calmness was flung to the winds. In the faint glow of the single lamp which he had switched on, Guy saw his face alight with excitement.

But he gave him one glance only. All his attention was concentrated on the spot over which that white flash had leaped.

He saw the surface of the calm sea violently ruffled as though a sudden gust of wind had struck it, and in the centre of this patch where, a moment before, the dark hull of the U-boat had been lying awash, he saw a sudden whirlpool open. Round and round swirled the short steep waves. Then suddenly their white spray vanished, and they turned to quiet swells.

Guy could not even answer. He could only stare at the great smooth patch where the oil-clad sea gleamed iridescent under the silver moon.

'The first neonite shell fired in war,' said Mr Ingram, and his eyes were aglow with triumph.

Guy looked in the direction in which the other was pointing, and saw a long dark shape tearing across the sea at almost the speed of an express train. From her three funnels flames glowed against the night sky; at her bow a white cushion of foam piled itself, while behind trailed a broad milky wake.

'A bit of a disappointment for her people,' said Mr Ingram, with a grim little smile.

The two fell silent while they watched the long swift ship come racing into the bay. Then suddenly her speed relaxed, and she was heading quietly towards the shining patch.

Guy ran back to the magazine, which was in a rock chamber cut in the edge of the cliff. A moment or two later a rocket went hissing skywards, flinging a trail of brilliant sparks behind it.

Almost at once it was answered from the destroyer, and then came the rattle of sheave blocks through the quiet air, and a boat plumped into the water, and was rapidly in to the landing.

CHAPTER VIII
STAPYLTON'S PROMISE

MR INGRAM and Guy reached the landing just as the boat came alongside the little stone-built jetty.

A smart young lieutenant at once leaped ashore. He stared keenly for an instant at the white-haired man and the powerfully-built youngster he found waiting for him there.

'We heard the firing, sir,' he said, addressing Mr Ingram. 'Commander Stapylton sent me ashore to ascertain what has happened. My name is Hope.'

'A U-boat has been shelling us, Lieutenant Hope,' Mr Ingram answered. 'But before she succeeded in doing any damage we sank her.'

Guy, watching Hope, nearly laughed. Never had he seen such an expression of amazement on any human face.

'You'll have to explain, sir,' he said. 'I never dreamed there was even a rifle at Galleon Gap.'

'Oh, we look after ourselves,' replied Mr Ingram, with a curious smile. 'But if you will forgive me, Lieutenant, I won't explain here and now. I should wish to see Commander Stapylton. I may tell you that there is more in this than meets the eye.'

'Will you come off at once, sir? I shall be delighted to take you out. And I'm sure the skipper will be only too glad to see you.'

'Very good. May my assistant come too? Let me introduce him. Mr Hallam—Lieutenant Hope.'

Hope made no objection, and the pace at which the boat travelled back to the destroyer was plain proof of the keenness of her crew to learn the explanation of what was to them an absolute mystery.

Arrived on board, it was clear that the whole ship's company were as puzzled as the crew of the gig, and at once Hope led the way to the Commander's cabin.

Commander Derek Stapylton was certainly not a day over thirty, but the moment Guy set eyes upon him he felt that here was the man for his money. Stapylton was not only remarkably good-looking, but his whole appearance gave an impression of strength and competence. Guy caught himself wishing devoutly that there had been a man like this at the Admiralty instead of that hopeless old fossil, Karslake.

'This is Mr Ingram, sir,' said Hope. 'And his assistant, Mr Hallam. They tell me that a U-boat was shelling them, and that they have sunk her.'

For a moment Stapylton looked almost as startled as his subordinate had been a few moments before. But he recovered himself quickly.

'I can't imagine how you did it,' he said. 'Still, there does not seem any doubt about it, for the Bay is one mass of oil. Perhaps you will explain, Mr Ingram.'

'That is what I am here for, Commander Stapylton,' answered Mr Ingram. 'I may tell you that I have works here, and that I have lately perfected an entirely new explosive. I call it neonite, and its result is to cause a complete vacuum over the area of explosion. The shell which I fired at the submarine contained only seven pounds of neonite, and to the best of my belief it did not actually hit her. Yet you yourself have seen what the result was. I have no doubt but that, if you could see the remains of the U-boat, you would find that she was opened out and burst from end to end.'

'I hope it means the end of war,' said Ingram earnestly. 'As a matter of fact, so terrible are the effects of neonite, that unless my country had been at grips with such a foe as Germany, nothing would have induced me to use it.'

'I am extremely glad that you have done so, sir,' replied Stapylton warmly. 'Even if you could do no more than destroy one of these pests of the sea, it would have been well worth while.'

'That is only the beginning, Commander. At least, I hope so. Neonite and the new gun from which I am firing it, will, I trust, not only end the submarine menace, but also smash Germany's military power for ever.'

'Indeed, it might well do so,' said Stapylton gravely. 'But why, may I ask, does our own Government know nothing of this invention, while the German is evidently quite cognizant of it? At least, I judge that he must be, for otherwise this U-boat would hardly have taken the risk of coming so close in here to shell you.'

'To the best of my belief, Commander Stapylton, the German's attempt to-night had nothing to do with neonite or my new gun. Their idea was to kill me and Hallam here. That was their object.'

'This is too much for me,' he said. 'And as I can see, Mr Ingram, that you have a story to tell, will you and Mr Hallam sit down and make yourselves comfortable. Then, perhaps, you will spin me the yarn.'

'I think,' he said, 'that you are the very man to whom I have been longing to tell the story.'

'I am glad to hear it,' said Stapylton, smiling in his turn. 'Please fire ahead.'

Mr Ingram had that great gift of putting things in few words, yet at the same time very clearly and convincingly. Beginning with the day on which Anson landed from the balloon, and the German plane was brought down by the first explosion of neonite, he told exactly what had happened up to the present. He dwelt particularly on the way in which Anson and Guy had been treated at the Admiralty, and he gave Dick Anson's story of the Secret City and its amazing ice-belt in full.

Stapylton and Hope listened in a silence that was the best tribute to their interest in what they heard. Neither of them moved or spoke until Mr Ingram had finished his last word. Then Stapylton drew a long breath.

'Well, of all the amazing yarns!' he said slowly. 'D'ye know, Mr Ingram, if any one had brought me a story like that three or four years ago, I should have recommended him to the editor of the woolliest fiction magazine I could think of. But the war has opened all our eyes. I believe every word that you have told me, and I promise you that I am going to interest myself quite a lot in this Secret City business. After all, it is exactly the sort of thing that the Huns might be expected to do, and as for the Cold Ray, there is really nothing more wonderful about it than wireless, and many other modern inventions. It doesn't beat your neonite.

'Still,' he went on, 'I can quite appreciate the fact that an old fossil like Karslake wouldn't swallow it, and the more so because it is quite true that wreckage from Q2 was picked up in the North Sea. I heard that myself two or three days ago. Now the question is, what are we going to do about it?'

'The first thing,' said Mr Ingram quietly, 'is for you to come ashore and see my gun and neonite with your own eyes. After that I think you should be able to interest some one who is big enough to induce the Admiralty to give both these inventions a real test.'

'Not a bad notion,' replied the other, 'though, for that matter, the test you have already made ought to be good enough for any one. The U-boat, I mean,' he added, with a laugh. 'Yes, I'll come ashore and see neonite with great pleasure. But it's late now, or rather early. I think I will resume my patrol for the present, and call upon you at a more reasonable hour in the morning.'

'Will you come to breakfast?' suggested Mr Ingram. 'We don't live luxuriously, but there will at any rate be new milk and fresh butter, hot scones, and coffee.'

'Topping!' declared the Commander, with a boyish twinkle in his eyes. 'Hope, there, is actually licking his lips. May I bring him, too?'

'We shall be delighted. And any other of your officers or crew as well,' replied Mr Ingram.

'I think Hope and I will be enough,' laughed the other. 'We don't want to eat you out of house and home. Meantime, can I offer you any refreshment?'

But Mr Ingram declined, and presently he and Guy were rowed back to shore, and about two in the morning got to bed and to sleep.

True to his promise, Commander Stapylton arrived at eight-thirty, and young Hope with him. Hannah had surpassed herself, and the breakfast was a real Yorkshire one, with scones hot from the oven, delicious eggs and home-cured bacon, rowan jam, and other delicacies, such as stewed whortleberries with fresh cream.

All did justice to the good things, and afterwards Mr Ingram showed the two officers his gun and the neonite. He exploded a cartridge of neonite, and Stapylton was absolutely thunderstruck at its extraordinary effects. When he left he had given his promise to do all he could to secure an Admiralty trial.

'I think,' he said, 'that you may consider the trial as certain. It will be my duty to report the destruction of the U-boat, and that in itself is a testimonial which the authorities cannot possibly overlook.'

'No, Hallam.' Stapylton's voice was suddenly grim. 'You may be very sure that I shall not forget that. And if the chance comes, I hope that you may have the opportunity of being with the expedition which must be sent to destroy it. To my mind, this gun and this neonite offer the best chances of tackling the infernal place.'

'I don't promise it,' said Stapylton quietly. 'But I will do my best for you. If any one deserves such a chance, you certainly do, Hallam.'

And leaving Guy fairly quivering with suppressed excitement, he went back to his ship.

CHAPTER IX
THE KIDNAPPING OF WALLACE INGRAM

TWO days later the weather changed completely. The sunshine gave place to clouds, it turned much cooler, and a strong breeze began to blow from the north-east. Guy, busy with Mr Ingram in the laboratory, did not pay much attention to the weather, but after their early dinner set off with Wallace for their usual tramp. Mr Ingram very wisely insisted that both the boys should get out for a good walk each day. He said that it was the only way to prevent getting stale.

This time the two made off along the top of the cliffs. They meant to visit the place where von Fromach's aeroplane had fallen, and see if any relics were left. The police and military had already removed the broken machine and buried the body of the dead German, but the place was so remote that there had been but few visitors to the scene of the smash.

There was nothing left on the spot, but a little way off Wallace found a twisted wire stay, while Guy discovered a button which apparently had come from a German uniform.

'Von Fromach's, I expect,' said Wallace, as he examined it. 'This is where we had to shove him along.'

'By the bye, Guy,' he went on, 'I wonder if he was in that U-boat we sank the other night.'

'Not likely,' replied Guy. 'I should say the chances are that the beggar is back in Germany by this time.'

'There's more than one U-boat around this coast,' said Guy. 'Maybe half a dozen, for all we know.'

'They won't be in a hurry to come messing round Galleon Gap again—that's one good thing,' chuckled Wallace.

'Rain coming, Wally. I felt a drop then. We'd best be sliding homewards if we don't want a ducking.'

Wallace nodded, and the two walked back to the coastguard path, which ran along the top of the cliffs. Guy was right about the weather. Out seawards a thin misty drizzle was already falling and driving steadily towards the land. The breeze had stiffened, and there was a constant crash of waves against the base of the cliff. The base of the rocks was rimmed with a line of white foam.

They were nearing the house, and the rain was really beginning to fall in earnest, when Wallace stopped and pointed seawards.

Guy looked. Away over under the Snout, the rocky point at the north horn of the Bay, two people were standing on the narrow strip of shingle which was still uncovered by the rising tide. One had a short, stiff sea-rod, the other a net which looked like a prawn-net. Behind them the cliffs rose steeply to a height of nearly a hundred feet.

'Doing!' echoed Guy grimly. Trying to commit suicide, I should think. Whoever heard of trying to fish from the Snout in weather like this?'

'I don't believe they can get out of it,' said Wallace. 'The beach is covered on both sides of them.'

'You're right, Wally,' replied Guy gravely. 'They can't. They're in a regular trap, and inside another half-hour the shingle they are standing on will be covered, too.'

'We can't let them drown, that's one thing certain,' replied Guy. 'Do you think we can get a rope to them?'

'I don't,' replied Wallace. 'Look at the way the cliff is broken. You can't get within yards of the edge.'

'That's the only chance so far as I can see. We might have taken the dinghy, but she'd never live in the surf that's breaking below the Snout.'

'That's out of the question,' agreed Guy. 'The sea there would swamp anything as small as she is. Well, come on. Let's get the rope and see what we can do.'

They found rope in the store-house, and tramped doggedly out towards the Snout, in the teeth of the rising gale. The cold rain cut their faces.

'And all for a brace of silly fool trippers!' growled Wallace, as he turned the collar of his coat higher around his ears.

'They'll be getting the scare of their lives,' said Guy. 'The wind's hardening every minute.'

Neither spoke again until they reached the seaward end of the Snout. Guy went as near to the edge as he could get, and looked over.

'Hurry, Wallace! There's no time to waste. The beach is almost covered. Here, tie the rope round my waist, and I'll go down.'

'You!' exclaimed Wallace. 'What's the sense of that? In the first place, you don't know the cliff, and I do. And in the second, you weigh half as much again as I do. No, I'm going down this time, Guy.'

Guy saw that there was good sense in what Wallace said, and as the climb was not dangerous or even particularly difficult, he agreed.

He fastened the rope carefully around Wallace's body, and Wallace at once went over the edge.

The face of the Snout was not sheer cliff. It was a mass of broken limestone, with fissures and crevices in every direction. An active man could have climbed all over it without a rope, so long as he started from the top. He could not, however, have climbed from the bottom, for the last ten or twelve feet were not only sheer, they actually overhung, the rock, having been cut away at the base by the sea.

Wallace, who was as active as a cat, went swinging down from one crag to another. Sometimes Guy could see him; then again he would be lost to sight. But the rope ran out steadily, and Guy was not in the least nervous about his sturdy chum.

At last Wallace reached the last ledge. Here Guy could see him plainly, and Wallace, turning, signalled to Guy to let out a good bit of rope. As has been explained, the last part of the cliff was a sheer drop.

Once under the ledge, he was again lost to sight. The strain on Guy was now heavy, but he had his feet wedged against a rock, and managed easily enough. It struck him, however, that it might not be quite so easy to pull him up again, while the two strangers would be heavier still.

Presently the strain relaxed, and by this he knew that Wallace had reached the beach. There wasn't much of the beach left now. The tide was coming up across it at a very rapid pace. The waves, however, were not large, for the Snout itself and the reef of rocks which ran out seawards from its eastern end gave some shelter.

There was a pause of some moments. Guy wondered what was happening. He gave the rope a turn round the rock on which he was bracing himself, and crawled forwards to the extreme edge.

Now really worried, Guy quickly made the rope fast around the rock, and, slipping off his coat, took firm hold of the rope and began rapidly scrambling downwards. Within a few moments he had reached a point from which he commanded a view of the narrow strip of shingle. He turned and looked down.

Close under the cliff Wallace lay helpless. His hands and feet were tied, and a gag was in his mouth. A few yards away were the two men. They were powerfully built, ugly-looking fellows, and having discarded their overcoats and flung aside their rod and net, now appeared in their true colours—as German sailors.

They were in the act of launching a large collapsible boat, which had previously been hidden among the great boulders which lay in heaps along the beach.

For the moment Guy was left breathless and horror-stricken. But only for a moment. Next instant he was himself again, cool and clear-headed as ever. He realised the whole plot in a flash. These were men from a German U-boat who had been sent to kidnap himself or Wallace, or both.

He glanced seawards. Sure enough, out there in the gray tumble he caught the slender top of a periscope emerging from the waves.

He realised that there were two courses before him. One was to hurry back at full speed to the house, get the gun to work, and destroy the sneaking, treacherous enemy. The other was to boldly descend to the beach, and, single-handed, tackle the two ruffians.

Naturally, it was the latter which appealed to Guy's fighting spirit. Yet his better judgment warned him that it was madness. These men, of course, were armed, and he himself had nothing—not even a knife or a stick. If he did go down, he had to swing the last part, and while doing so would be absolutely at the mercy of the enemy. He would be dangling helpless at the end of the rope.

For a few seconds he paused in miserable hesitation. It was a dreadful dilemma, for every instinct fought against leaving Wallace in the hands of these scoundrels, while he knew—no one better—how small the chance was of being able to get back in time to use the gun.

The men had the boat in the water. One held it firmly, while the other dashed back and, picking up Wallace bodily, swung him roughly over his shoulder.

With a groan, Guy realised that one chance was gone. He could not reach the beach in time to stop them. Even now he hesitated. He stooped and picked up a large stone. It was in his mind to try to fling it into the boat. But on second thoughts he dropped it. The boat was so far away that he could not possibly hit it. And the fall of the stone would only betray him to the Huns, who would certainly shoot him down before he could get away.

Guy turned, and in a state of mind that was quite beyond description, he began climbing swiftly back up the rope.

Arrived at the top, he glanced back. The boat was already safely launched, and the two men were at the oars pulling hard towards the stick-like periscope which still protruded from the short, foam-capped waves.

That run home was a nightmare. Guy's lameness did not prevent his walking as well as any man, but it did hang him up in running. He arrived dripping with sweat, panting, hardly able to breathe.

He rushed into the laboratory. Mr Ingram, busy at his work-bench, turned, and the first glance warned him that something very serious had happened.

'Wallace!' gasped Guy brokenly. 'The Huns have kidnapped him. The gun—our only chance.'

Ingram understood at once. His face went white as death, but he did not hesitate. Turning, he ran towards the gun-shed, and Guy, though almost done for, staggered heavily after him.

He found the inventor standing at the mouth of the shed staring out at the sea. Hearing Guy he looked round, and the expression of despair upon his fine old face wrung Guy's heart.

CHAPTER X
THE HUN OFFERS TERMS

TOO late! Too late it was. Guy saw that at a glance. The U-boat was now on the surface, and the collapsible already within less than a hundred yards of her. A charge of neonite would undoubtedly sink the Hun, but at the same time must infallibly destroy the boat and its occupants.

'I—I tried,' said Guy thickly. But Wallace's father did not seem to hear. He stood in stony silence, gazing out at the tragedy which was taking place before his eyes. His boy, his only son, was in the hands of the ruthless enemies of himself and of his country.

The U-boat's conning-tower hatch was open. She lay awash. In this thick weather there was little to fear from British patrols. In misery too deep for words, Guy saw the boat draw close alongside, under lee of the Hun vessel. He saw Wallace lifted and roughly slung aboard. He was carried up the ladder into the conning tower, and vanished down the hatch.

Then the men in the boat dragged it on to the narrow deck of the submarine, and with incredible quickness it was folded up and passed below.

They followed, the hatch clanged down, and almost instantly the U-boat began to submerge. Another half minute and the gray waves were breaking over the spot where she had vanished.

'It was my fault,' he ended bitterly. 'I ought to have gone down on to the beach and tackled them.'

Mr Ingram looked at Guy, who stood, with head hanging, the picture of misery and shame. Even in his own sorrow he found it in his heart to pity the boy.

'No' he said quietly. 'I do not think so. If you had done so they would have had you both, and as for me, I should never have known what had happened.'

'Not in the least. You have done your best, as you always do. Now, come back to the house, and we will think what is best to be done.'

Guy lifted his head, and the look of relief in his face was wonderful to see. To feel that Mr Ingram did not blame him lifted a great load from his heart.

'It is you and I against Germany now, Guy,' he said. 'Remember, we still have neonite.'

'But can we use it, sir?' returned Guy bitterly. 'They will hold Wallace hostage against us now.'

'That is true. One U-boat, at least, is sacred from us. Guy, we are neither of us able to think clearly. We must have help. We must get hold of Vassall or of Commander Stapylton. They will advise us what is best to do. I have Vassall's address in London. You must take a wire to the office at once.'

Guy, only too glad to be able to do anything useful, went off at once with the wire. He sent it reply-paid, and arranged to have the answer sent out to Claston as soon as ever it arrived.

Then he came home again. Tea was ready, but neither he nor Mr Ingram could eat. Both were haunted with the idea of poor Wallace prisoned in the sickly atmosphere of the U-boat cruising out somewhere beneath the surface of the stormy sea. The weather was growing steadily worse, and a great gale was raging across the moors. The cliffs seemed to shake under the pounding of the giant rollers.

They sat up late, waiting for the answer from Vassall, but it did not come. Hannah, herself in tears, did her best to tempt them with a dainty supper, but Wallace's empty place made it impossible for them to sit long at table. At last they went sorrowfully to bed.

Tired as he was, Guy lay for hours, unable to sleep, going over and over the whole scene in his mind, trying to convince himself that what he had done was the best, yet feeling all the time that he ought to have been alongside Wallace in his peril.

At times he wondered what the Germans would do with Wallace, now that they had him. They would not murder him, that was one thing certain, for he felt sure that they were holding him as hostage.

Next morning broke dull and wet. The gale had fallen, but the skies were gray and dismal as his own thoughts. Guy looked to sea, but the tumble of short waves was unbroken by any craft. Not even the smoke of a destroyer trailed across the horizon.

The morning dragged on. Post came, but no word of Vassall. Mr Ingram looked ten years older than he had on the previous day.

By dinner-time the sea had quite gone down, but a fog had closed in. They could see nothing beyond a radius of about a hundred yards.

'Guy,' he said, 'I cannot stand this suspense. I think you had better go up to London and see if you can find Vassall.'

There was a ring at the bell. Without waiting for Hannah, Guy ran out. A disappointment was in store. The man who stood at the front door, with Fan, the terrier, sniffing suspiciously at his ankles, was a complete stranger.

Guy gave him a quick glance, but could not size him up. He was a man of middle height, sturdily built, dressed in an ordinary blue serge suit, and carrying a dark mackintosh over his arm. His face was as undistinguished as the rest of his appearance. He might have been a commercial traveller or any ordinary business man.

'Stebbins,' replied the other. 'If you will allow me, I will explain my business to Mr Ingram.'

Guy thought the stranger's manner was a little too polite. He hesitated an instant. Then came Mr Ingram's voice from the door of the laboratory.

Stebbins eyed him oddly, and now Guy noticed for the first time that the man's eyes were peculiarly keen and penetrating.

'It is rather, I think, a question of what I can do for you, Mr Ingram,' he answered. 'By the bye, I presume we are safe from interruption?'

'Perfectly,' said the inventor. 'There is no one else in the place but my housekeeper.'

'I have my suspicions,' replied Ingram. Guy understood that he was not going to give anything away until he had learnt how much Stebbins knew.

'Who are you?' he demanded. 'Who are you who make excuses for our brutal enemy?'

'Does that really matter?' he asked. 'It should be sufficient for you that I am able to restore your son to you.'

Ingram quivered all over. For a moment Guy thought he was going to hurl himself on the man. He himself tingled in every vein. Stebbins was a Hun. There was no doubt about that.

'I am at your mercy,' he said. 'If you wish to do so, you can either kill me or take me prisoner, in which case, of course, I should be hung as a spy. But kindly remember that such a proceeding will not help your son, who will then be definitely lost to you.'

The inventor put his hand to his throat. He seemed to Guy to be almost choking. Stebbins remained unmoved.

'You say you are able to restore my son to me. I suppose I must degrade myself to listen to your terms.'

'You will, I think, find it advisable to do so,' returned Stebbins, in a level voice. 'They are not severe. Briefly, all that we require is the secret of your new explosive and a sample of it. You hand us this, and your boy will be returned perfectly safe and unharmed.'

'You blackguard!' he said. 'You have the insolence to demand that I should betray my country. No! A thousand times, no! Rather would I lose a dozen sons, if I had them, than hand over to you the means of destroying England.'

'Not quite that,' replied Stebbins calmly. 'I cannot prevent you from using it also. I only wish to even matters, so far as possible.'

'It is not a matter for argument,' returned the inventor sternly. 'Go back and tell your chiefs that I utterly refuse to entertain your terms. Murder my son, if you will, but remember that for every drop of his blood I will claim a score of lives from Germany.'

'Fine talk!' said Stebbins, but although his voice was cold as ever, there was an ugly gleam in his eyes. 'But it is my duty to inform you that from to-day onwards your son will be deprived of food unless I return with a favourable answer.'

'You foul brute!' he cried, and springing at the fellow, caught him by the throat.

Stebbins's face went dusky red, yet he never moved or made the slightest attempt at resistance. You cannot throttle a man who will not fight. Guy's hands fell away. He dropped back and stood looking at the fellow as one might look at a horned viper or some equally abominable reptile.

'In war there is no humanity,' said Stebbins. 'As a man, I regret the necessity of the steps we are obliged to take; as a German I have no such regrets. Once more, may I suggest to you, Mr Ingram, that you should be wise and agree to the terms that I have been deputed to lay before you?'

'Once more, let me assure you that nothing that any German can do will induce me to agree to your terms, or to become a traitor to my country,' returned Mr Ingram, in a tone of ice. 'And were my son to know of the shameful terms which you have proposed, he would be the last to urge me to accept them.'

'He may change his mind in a day or two,' replied the so-called Stebbins, in his level voice. 'You, too, may do the same after due reflection. In such a case you have only to fly a flag—a white one, if I may suggest it—above this house. But do not first warn your own naval forces. The boy will not be given up on any other terms than those which I have had the honour to put before you. And if the vessel in which he is at present imprisoned should be attacked, he will be the first to perish.'

Then followed a dead silence. Guy was too angry to speak. As for Mr Ingram, though outwardly calm, Guy, who knew him so well, realised that he was at the very end of his endurance.

Mr Ingram glared at the man for a moment, and Guy, watching him breathlessly, wondered what would happen. But the old inventor still retained his wonderful self control.

'You can go,' he said. 'It is not for me to deal with such as you. God will do that.'

He spoke with a cold passion which for once seemed to pierce the hide of the Prussian. His eyes fell, then suddenly he turned and hurried out of the room.

'No. It would only mean that I should lose you as well as Wallace,' answered the other. 'Let him go. I meant what I said. A higher Power will deal with such as he.'

If Claston had been a sad place during the past twenty-four hours, now the gloom was almost unendurable. Once the German was gone, Mr Ingram went straight to his own room and locked himself there. Guy, sick at heart, could picture to himself the horror of that awful hour, when duty to his country struggled in the old man's heart with love for his only son.

Guy himself was but a degree less affected. Indeed, he was nearly desperate. He could not rid himself of the idea that he was in some measure responsible for the awful plight of Wallace. It had been bad enough to know him to be prisoner in the hands of the Huns. To think of him as slowly starving to death inside the narrow hull of the U-boat was enough to reduce Guy himself to madness.

Suddenly Guy remembered what Mr Ingram had been saying just before the arrival of the German envoy—that he had wished Guy to go to town and try to find Vassall. It was now too late to catch the 4.30, but there was still the night train. Any action was better than sitting still and brooding. He went out and got the car ready for the drive to the junction.

He came in again and asked Hannah to get him some tea. Little as he felt like eating, he knew that he must keep going. Then he went to his room and packed a bag.

He found that he had not enough money for the journey, and realised that he must ask Mr Ingram for what he required. Yet he hated the idea of going to his room and disturbing him.

While he hesitated, Fan, the terrier, began to bark again, and suddenly he heard Hannah's voice calling him from below.

Guy's heart leaped, and he hurried into the sitting-room. There stood the Secret Service man, calm and cool as ever.

'Wallace,' answered Guy. 'Wallace has gone. The brutes have got him aboard a U-boat. Oh, Mr Vassall, they are going to starve him to death.'

Guy's voice broke. There was a lump in his throat, which he strove in vain to swallow.

'Steady, Hallam; steady!' came the other's quiet voice. 'Sit here and tell me all about it.'

CHAPTER XI
FRESH TREACHERY

GUY was ashamed of giving way even for a moment. With a big effort he pulled himself together, and managed to tell Mr Vassall exactly what had happened during the past twenty-four hours.

Vassall listened in silence, yet Guy had a comforting feeling that he was not missing a word. There was a certain quite strength about the Secret Service man which was strangely helpful.

'Yes,' said Vassall thoughtfully, when Guy had finished his story, 'I quite agree with you, Hallam, that it is an ugly business. And for the boy's father it is simply abominable.'

'They are quite capable of it,' replied the other. 'Yet on the other hand, I don't suppose for one minute that they really will do so. They will put the boy on very short commons, no doubt, but they will hardly be fools enough to risk his life. You see, they hold him as a trump card, and so long as he is alive they can always work on his father's feelings. No, I think you can take it from me that they will certainly not starve him to death.'

'What is that you say?' came a hoarse voice, and looking round they saw that Mr Ingram himself had just entered the room. 'What were you saying, Mr Vassall?'

'I was telling Hallam that I do not believe in the threat of this Hun, Mr Ingram. It is fairly certain that your son will be kept very short; but I feel sure they will not risk actually starving him.'

'You put fresh hope into my heart,' declared the elder man. 'I thank Heaven you have come. But you never answered my telegram.'

'Ah, but I was not in London. I have been in Yorkshire these three days. I have been on the track of this man Cratch.'

'Do you know,' he added, 'I am strongly inclined to believe that the man who called on you this afternoon was Cratch himself.'

'Impossible! I have seen Cratch several times. He was quite an elderly man. He looked about sixty, and had a little gray moustache and side whiskers. Stebbins was years younger, and clean shaven.'

'Even so, I have not much doubt that they are the same,' said Vassall. 'In reality this man is neither Cratch nor Stebbins, but a Prussian whose name is Steubel. He is one of the very cleverest of their spies, speaks English and French as well as his own language, and has as many disguises as a chameleon. He was on the stage at one time, and well-known as a character impersonator. It was his cleverness at this sort of thing which attracted the attention of the German Secret Service, and they got hold of him at once.'

'It's very hard to believe,' said Guy slowly. 'I never saw two men more unlike. Tell us, how does a fellow like that hide himself?'

Vassall smiled. 'I only wish I could. He is as cunning as a dog-fox, and the mere fact that he is able to alter at will not only his clothes but his face, figure, even his voice, makes it desperately difficult to get hold of him.

'Still,' he went on, 'it does not matter for the moment whether the man is Cratch or Stebbins or Steubel. The fact remains that he has brought you this message, and that the message is undoubtedly genuine. It is now up to us to devise some means of foiling these people.'

'I do not see why we should not. Guile must be met by guile, and I have already a sort of idea in my head. But in a matter like this, where the issues involved are so great, I dare not act on my own responsibility. I must first get into communication with my chief. Is your car in order, Mr Ingram?'

'I had just got her ready when you arrived, Mr Vassall,' said Guy. 'I can take you anywhere in her.'

'The nearest post office, that is all,' smiled Vassall. 'If we start at once we ought to get there before it closes for telegraphic work.'

'Don't trouble to bring her round,' said Vassall, picking up his hat. 'I'll come with you.'

'Don't worry, sir. We will settle this thing somehow or other. For your comfort, I may say that the news of how you sank the first U-boat has already created a considerable sensation at the Admiralty. I think that I can promise you that you shall have the whole weight of the British Government behind you. Good-bye for the moment. I shall probably be back with Hallam, and if so will ask you to put me up for the night.'

Then he was gone, and a few minutes later he and Guy were whirling across the moor. There was still plenty of daylight, and although the clouds were low and heavy, fortunately no fog.

Guy noticed that the Secret Service man had an ugly-looking automatic ready at his side, and that he was keeping a very sharp watch in every direction. But they saw no one at all in all the length of the lonely road, and pulled up safely at the Post Office in plenty of time to send their message.

Vassall wrote a long telegram in code, and despatched it to a code address in London.

'Now we must wait for an answer,' he said. 'The postmaster is going to keep the office open for me. Meantime, I suggest that we shall go and get some supper. You look as if you were hungry, and I know I am.'

Guy was hungry. He had eaten very little during the past twenty-four hours. He had been too miserable. Now that hope had returned, so had his appetite, and he and Vassall made a really good meal at the little hotel.

They had not much more than an hour to wait before the reply came. Vassall rapidly decoded it, and frowned a little as he read the message.

'They want to see me,' he said. 'I shall have to go up to London. What trains are there?'

'Capital! Then I will take that. As for you, you had better go straight home while there is still light. Tell Mr Ingram he will hear from me in the morning. I shall telegraph early. The message will be in code, but here is a book from which you will be able to decipher it. Good-bye, Hallam, and keep your spirits up.'

Without having any particular reason to feel more cheerful, Guy's spirits certainly were raised a lot, and when he reached Claston he found that Mr Ingram, too, was less miserably anxious than he had been.

Next morning it was hard to say which was most eager to hear from Vassall. It was about eleven when the messenger whom Guy had specially arranged for on the previous night arrived on horseback with the telegram.

Mr Ingram's fingers shook a little as he tore open the buff envelope and compared the message with the code book. Guy saw his face change.

'Good Heavens!' he exclaimed, in utter amazement. 'He says we are to accept the German terms.'

'Yes, here it is in black and white. "Accept German terms. Fly the flag. When the meeting-place is arranged wire to address given or leave word with Hallam. Go fearlessly to the arranged spot. Vassall."'

Guy wasted no time in obeying orders, and though it went much against the grain, flew the white flag of truce on the staff above the house.

Nothing showed, and time went on without anything happening. Mr Ingram's face grew more and more strained. At last, just before dusk, from nowhere in particular, an elderly working man came up to the house and asked to see Mr Ingram.

Guy stared at him. He wondered if it could possibly be Steubel, but decided that this was out of the question. This man's face was quite different in shape. He was shorter and squarer than the German.

'Ah coom about that theer flag,' he said, in broad Yorkshire, and Guy, badly puzzled, took him in to see Mr Ingram.

The man did not speak, but simply handed a note to the Inventor. Mr Ingram read it and handed it to Guy. It was written in English, and ran as follows:—

'To Mr John Ingram. Be good enough to accompany the messenger, bringing with you the sample and formula, as arranged. You will come alone, please. (Signed) Ezra Stebbins.'

'Of course I shall go,' replied Mr Ingram curtly, but there was something in his eyes which reminded Guy of what he had to do.

Rapidly Mr Ingram put on hat and coat, and picking up a parcel which he had already prepared, followed the artisan out of the house.

The messenger led the way northwards along the edge of the bay, and Guy watched them both keenly for a few moments. Then he dashed into the sitting-room and wrote the telegram for Vassall.

There was a messenger waiting, concealed in the garage. Guy had seen to that already. He was Tyrrell, one of their own men, and Guy knew that he could trust him. Another moment and the car was buzzing off for the post office at full speed.

Guy looked out again. Mr Ingram and his companion were just disappearing in the direction of the Snout. Guy took an electric torch and a pistol, slipped on an old heather mixture coat which would tone with the surroundings, clapped a cap of the same colour on his head, and set out on their trail.

He did not follow directly, but struck a trifle inland. He knew every fold of the moor, and was sure that he could keep the others in sight while remaining himself unseen.

Guy's slight lameness prevented his running fast, but did not interfere with his walking. He gained rapidly on the others, and was soon parallel with them, but some quarter of a mile inland.

The sun was down now, and dusk was beginning to close in. But it was a fine evening, and the air very clear after the recent rain. He had no difficulty in keeping his eyes on the pair who were travelling steadily along the cliff path.

Suddenly he became aware of a third person. A man lay behind a gorse bush between Guy and the sea. He was watching the coast path. Instantly Guy realised that he must be another of the Hun spies, and he congratulated himself on his foresight in having come so far inland.

He saw that the Germans meant to make sure against any one following to their secret rendezvous, and as he thought of their cruelty and treachery his heart hardened, and he made up his mind that this fellow should not prevent him from going where he pleased.

Without the slightest hesitation he set himself to stalk the man. His heart beat a little faster than usual as he moved silently from bush to bush. Just beyond was a small hollow, a sort of trough which sloped gently seawards. It gave Guy just the shelter he wanted, and the beauty of it was that it led quite close alongside the gorse clump where the Hun was lurking.

Intent on the coast path, the man never dreamed of looking round behind him, and Guy was right upon him before at last some sixth sense warned him, and he turned.

The moment Guy saw his face he realised that this was a real Boche. There was no mistaking the beefy face, bristly fair hair, and pale blue eyes.

Guy gave him no time to shout or signal. He was on him like a tiger. The German had a heavy leaded stick, and tried to swing this up to hit his adversary over the head, but Guy was too quick for him. He caught his right arm before he could raise it, and pushed him violently back, at the same time crooking his left heel behind the other's right leg.

Over went the Hun flat on his back, and as luck had it, caught his head on a rock which stuck out just above the thin turf. There was a sound like a mallet meeting stone, and Master Hun crumpled and lay quite still.

Guy held him a moment to make sure he was not fooling, then taking a length of cord out of his pocket, rapidly tied him hand and foot, and finished by gagging him neatly.

He looked up. Mr Ingrain and his guide were just disappearing in the distance. Guy jumped to his feet and hurried after them.

Things had gone well so far, and Guy's heart was thumping again, but now with pleasurable excitement. This was his first real tussle with a Hun, and he felt he had done well. He could not help being pleased with himself.

He noticed that the pair he was following were making for a break in the cliffs about two miles beyond the Snout. Galleon Gap itself was a fairly remote sort of place, but this little inlet, known as Cleft Bay, was even farther from civilization. There was not a house of any sort in sight, and the Bay itself was never used as an anchorage because the mouth of it was one tangle of rocks. A more dangerous place for any one who did not know it could hardly be imagined.

These rocks were called the Singing Reef, and it was not a bad name, for even in calm weather the sea was always talking and the swift tides humming among them.

'Great Caesar!' muttered Guy. 'They can never have got a U-boat into that place.'

Yet, as he came nearer, there was no doubt whatever but that the man had taken Mr Ingram down the cliff path leading to the Bay. The tide was on the ebb, and there was a strip of shingle bare beneath the low cliffs.

As he came nearer, Guy moved very cautiously, and kept his eyes lifting for a sight of any stranger. But be did not see a soul, and presently he was safely ensconced behind a sturdy gorse bush close to the edge of the cliff.

By this time it was getting late, and the daylight almost gone. But there was not a cloud in the sky, and the evening was so wonderfully clear that he could still see to a considerable distance.

Peering over the edge, he spotted Mr Ingram and his guide on the beach below. The guide disappeared behind some rocks, to emerge again in a moment, pulling a collapsible boat down to the water.

He launched it. Mr Ingram got in, the other followed, and began to pull out into the bay.

Guy stared out across the calm, gray water. Next minute he distinctly saw a slender pole with a small knob at the upper end rising above the sea out in the centre of the bay.

He could hardly believe his eyes. How a U-boat had sneaked in through the narrow and perilous passages in the Singing Reef seemed a perfect miracle. But there she was, for a moment later her conning tower lifted silently out of the water, and the long, low, sinister shape of her was plain to see.

Now Guy's heart began to pound again. Wallace was somewhere hidden in the hull of the enemy ship. Would the Hun keep his word and restore him in exchange for the formula? Then Guy began to think of Vassall. What was he doing? It was not to be supposed for a moment that the powers whom he represented had the least intention of allowing the insolent U-boat to go scot free. He glanced seawards, but there was no sign of any vessel out in the offing.

He turned his eyes back to the boat. She was rapidly nearing the enemy craft, and he watched her till she came alongside. As she touched the steel coaming of the U-boat, two men emerged from the hatch in the conning-tower, and came quickly down on to the narrow deck. There was not light enough left to see their faces, yet Guy, leaning eagerly forward, was almost certain that one was von Fromach. That squat, toad-like body, the enormously deep chest, and the arms of baboon-like length—there could hardly be two people of such extraordinary build.

Mr Ingram did not move from the boat. Guy saw that he was speaking to the Germans, but at this distance he could not hear a word that he said. Then he saw that von Fromach—if it was von Fromach—was evidently inviting him to come aboard.

Apparently Mr Ingram did not wish to do so, for he remained where he was. He seemed to be expostulating.

All of a sudden the two Germans sprang forward. At the same time the guide seized Mr Ingram from behind and shoved him violently forward. Von Fromach and the other caught hold of him, and dragged him aboard.

The old inventor tore himself free, and hit out pluckily. It was no use. All three closed upon him, and before Guy's horrified eyes he was dragged up the turret ladder and down the hatch. Guy heard the hatch clang to behind him, and saw the U-boat at once prepare to submerge.

CHAPTER XII
THE DETECTOR

DOWN she went, sliding under water like a great seal. For a moment or two her periscope showed above the water, then that, too, was gone, and only little swirling waves showed where she had vanished into the depths of the bay.

'What else could one have expected?' he said bitterly. 'Any one might have known they would never let Mr Ingram go once they had him in their hands.'

He dropped again on to the short turf and lay there, staring out through the gathering darkness. There was nothing to be done now. Vassall was too late. It was all over. The U-boat had nothing to do but crawl out by the way she had come, and, remaining submerged, carry her prisoners back to Germany. She would creep through the mine-fields and land Mr Ingram and his son at Kiel, or some other Hun port.

It did not need much thinking to realise what would happen then. Neonite would at once be manufactured on a large scale, and within a few weeks it and the Cold Ray would come into effect on the Western Front.

Then—then what earthly chance would our poor fellows have? Frozen to death, blasted out of existence, the whole Western Front would be not merely broken through, but actually destroyed, and the brutal enemy would march through, unharmed, seize Paris, and dictate terms which would lay the world in slavery under his iron-shod feet.

If Guy had been wretched when Wallace was seized, his feelings then were nothing to what they were now. It seemed to him that his world was crumbling around him. Vassall had failed him. How could it be otherwise, for even by now the telegram would hardly have reached him? Long before he could arrive, the U-boat would be far beyond reach of pursuit.

Quite suddenly Guy sprang to his feet. A new idea had come to him. The original formula of neonite—surely that was still in the safe! Although Mr Ingram had not said so, it must have been only a copy that he had taken with him. If the original was still there, the situation might still be saved. Vassall had said that the British Government were awake to the situation, and if neonite could be manufactured by them in large quantities and hurried to France, the Allies might still get ahead of the Hun and smash him before he could smash them.

Full of this idea, he turned and started back for Claston as quickly as his lame leg allowed him to travel.

'Y—yes. But you're too late. They've got him. The brutes have broken their word and kidnapped Mr Ingram just as they did his son.'

'Did you expect anything else?' asked the Secret Service man, in a tone of mild surprise.

'Of course. You and I know by this time that the Hun never keeps his word unless it suits him to do so. I assure you, Hallam, that we were all quite certain that this was what would happen.'

'But it has happened,' urged Guy. 'And now it is too late. The U-boat has gone under. By this time she is probably a mile outside.'

'No need to get so worried, Hallam. She isn't a quarter of a mile from us this minute.'

'Look at the tide. It is still falling. And I happen to know that there is not water enough for any U-boat to creep out until half flood.'

'Don't. There is no need. But you may take it from me that I am right. Fritz is smart, but when I tell you that I have known this coast since I could walk, there is nothing wonderful in my being well up to him in my depths and charts. I believe I could give you the soundings for ten miles on either side of Galleon Gap.

'You see, Hallam,' he went on, 'the minute you told me of Steubel's suggestion, I made up my mind that this would be the rendezvous, and I made all my arrangements accordingly. It was just because this is about the last place that any one would look for a U-boat that I felt sure the beggars would pick upon it. As a matter of fact, I never went to town. I met my man at Sheffield and came straight back. But everything is fixed up, and now we can get to work.'

'But how?' asked Guy anxiously. 'Of course I know that if the U-boat is still in the bay we could use a depth charge and smash her up, but if we did it would be the end of Wallace and his father, too.'

Outside the reef, faintly outlined against the darkening sea, lay a long, black, silent shape.

Guy's eyes were shining. It seemed to him that his highest ambition was about to be realised.

'A very risky one,' Vassall continued, and his quiet voice had a sudden tone of gravity. 'It is quite on the cards that none of us will come back.'

'We've got to come back—and bring Mr Ingram with us,' said Guy. 'The country needs him.'

'I forgot. There's a Hun about half a mile back. I caught him and tied him up. He'll probably die if we leave him there.'

'I saw the whole business,' replied Vassall, with a smile. 'I was only a few hundred yards away. It was a neat job, Hallam, and I congratulate you upon it. As for the German, I had a man with me, and told him to bring the prisoner on. He may be useful to us.

'Ah, here they are,' he said, glancing round, and Guy saw a man in blue jacket dress coming towards them, escorting the Hun, who had his hands tied and looked very sorry for himself.

'Come, Hallam,' continued Vassall, and turning to the left led the way to the cliff path.

By this time a boat had left the British submarine and was coming quickly to the beach. Guy noticed that she landed at the outer angle of the little bay.

'We don't want to scare the Hun,' explained Vassall. 'You know all modern submarines are fitted with a microphone, or mechanical ear, and they would hear even so slight a sound as the beat of oars if the boat came anywhere close to them.'

'But I don't understand yet,' protested Guy. 'What good is the British submarine going to do? She can't see the U-boat, and when the tide is high enough the Huns will be able to sneak out under water.

'Of course,' he added, 'it would be all right if we could blow her up, but we can't.'

'Bombs and depth charges are not the only weapons we possess with which to fight U-boats,' he said. 'Sit tight, and you will soon see what I mean.'

Guy said no more. He was badly puzzled, yet trusted Vassall, so he followed quietly to the beach.

The coxswain in charge of the submarine's boat seemed to know Vassall. He touched his cap, and said a few words in a low voice. Guy could not catch Vassall's answer, but Vassall stepped aboard, Guy followed, and they started.

Guy was conscious of a feeling of strong excitement as they approached the British submarine. In all his life he had never been aboard a boat of this class, and now he was not only going aboard her, but, from what Vassall had said, apparently going to share in some strange and dangerous expedition.

His breath came quickly as he stared at her. She was larger than the U-boat, longer and broader. She looked like a great steel shark ready to swoop upon her prey.

As they came alongside a figure showed suddenly in the conning-tower. A young man whose keen face was silhouetted against the darkening sky.

'Hallo, old son,' came Dick Anson's familiar voice. 'Jolly glad to see you. Come aboard.'

Guy jumped lightly on to the steel deck, and a moment later his and Dick's hands met.

'You needn't explain,' said Dick quietly. 'I've heard about Wallace, and as for the other game, I spotted that with my own eyes. I was lying just behind that tall rock at the end of the reef there. They landed me there a couple of hours ago to see what was up. We've had Fritz under our eyes the last two days, only he didn't know it.'

'Steady, Guy!' said Anson quietly. 'Of course we could have slammed a "mouldy" into her, but if we had there'd have been an end of Wallace. Besides, these things are not in your hands or mine. There is a bigger game afoot. You'll hear all about that in due time.'

He turned to speak to Vassall, then, as the boat went back for Vassall's man and prisoner, took Guy and Vassall below.

Guy hardly heard Anson. He was looking all around at the extraordinary mass of machinery which seemed to fill almost the long, tunnel-like interior of the submarine. Wheels, pistons, dynamos, gauges of all descriptions, and everything gleaming under the strong glow of the electric light.

Guy was so taken up with it all that he did not even see the broad-shouldered, deep-chested man who came out of the little stern cabin to greet his visitors.

'So you are the lad who helped to strafe the U-boat,' said Mostyn, as he gave Guy's hand a hearty grip.

'Well, we have another job of the same sort on hand, but a bit bigger. I must have a yarn with you about this electric gun. 'Fraid we can't mount it in Q17, but I rather fancy the idea myself.'

Guy flushed at the pleasant words, and felt that he was going to like Mostyn at once. Meantime, Mostyn was speaking to Vassall, and Guy got a chance of another look at his strange surroundings.

Next thing he knew, Mostyn was suggesting supper. Guy had been under a sort of impression that in submarines people lived on sardines and cocoa. He was pleasantly disappointed to find a capital little meal consisting of fresh whiting grilled on an electric stove with fried potatoes, a fruit salad, cheese and biscuits, and a cup of capital coffee to top off with.

He ate with appetite, but at the same time he was burning to know what was going to happen. Mostyn, however, and Anson never referred to the matter until the coffee appeared.

Mostyn nodded. 'After all, it don't make much odds. Night's so clear we shan't have any difficulty in seeing her.' He turned to Vassall.

'It was only fog I was scared of,' he added. 'Even then, unless it had been pretty thick, we could hardly have missed her.'

'You have the detector fixed?' asked Vassall, with a shade of anxiety in his voice.

'You bet we have,' replied Mostyn, with a smile. 'Three of 'em in all. Of course there's only one real channel out through the Singing Reef, but we thought we'd be on the safe side. She can no more escape running into one of them than a fly can get off a sticky fly-paper.'

'Don't tell him, skipper,' he said to Mostyn. 'Let him see for himself. He's a blooming inventor. He ought to be able to tell us all about it.'

Guy looked from one to the other, but saw that he was not going to get anything out of them.

'No need to wait if you don't want to. You can turn in if you like,' replied Dick lightly.

'Turn in!' retorted Guy. 'What—with Mr Ingram and Wallace prisoners in that beast of a U-boat!'

'Don't apologise, Hallam,' he replied quite gravely. 'As a matter of fact, your feelings do you credit. But Anson, there, would always try to pull your leg, even if we were lying at the bottom, with the whole German navy strafing us.'

'I won't tell you what the gadget is,' he added. 'But it's a top-hole notion, and you may take it from me that Fritz will never get out of Cleft Bay without our knowing all about it. And here's for your comfort. We can collar the U-boat and rescue your friends almost any time we like, only we don't propose to do it quite yet.'

'Anson, if you've quite finished with the coffee-pot you might pass over what's left, and then take Hallam on a tour of inspection. I'm sure he's dying to see how the wheels go round.'

'Right!' grinned Dick. 'It'll be a new experience for the simple sailor to give lessons to the young inventor.'

For the next hour or so Guy was in a sort of fairyland. Always mad on machinery, he had read all there was to read on the subject of under-water craft. Now, for the first time, he had the chance of seeing the very latest of her kind, and so interested was he that he almost forgot for the time the peril of his friends. Dick himself was very keen on his job, and knew his ship inside out. He had never had a more appreciative listener, and even he was surprised to find how much Guy knew of all the intricate machinery which filled Q17.

Time slipped away, and Guy was surprised when Dick, glancing at his watch, suddenly said, 'Eleven o'clock. We'd best go on deck, Guy.'

The night air struck fresh and cool as they emerged from the hatch into the open. A three-quarter moon was just lifting above the hills inland, and shed a pale silvery light over the calm sea.

Mostyn and Vassall were already on deck, and both staring in the direction of the mouth of the little bay. The tide was running in fast. Guy could see that rocks which had been almost bare when he came aboard were now nearly covered.

'Not yet. But there's plenty of time. From what Mr Vassall says, there is barely water enough yet for her to creep out. He says she'll come from there,' pointing to a gap between two ugly-looking crags.

'That's just what we thought, wasn't it, sir? Well, she'll go slap into it if she does.'

Silence fell among the four. Guy could hardly breathe for sheer excitement. The minutes dragged by, and the moon rose slowly higher until the clear air was flooded with her pale light.

Guy's eyes were glued upon the gap between the rocks. He saw, or thought he saw, a thin stream of bubbles rise and break upon the surface. But he himself could not feel sure that it was not the strong tidal stream swirling against the rocks of the reef.

Vassall did not answer. He seemed hardly to hear. As for Guy, he was screwed up to such a pitch of excitement as he had never known.

Guy, looking in the direction indicated, was conscious of a curious disturbance in the water. About a hundred and fifty yards aft of Q17 a small spout of foam was rising from the sea. It looked as though a baby whale were blowing, only that the spout was not stationary. It was moving quite rapidly across the surface.

'Plenty of time, Mr Vassall. Plenty of time. She's a shy bird, and we don't want to scare her. Still, I think I'll give orders to proceed. No, there is no need to come below. We shall travel on the surface for the present, at any rate.'

CHAPTER XIII
ON THE TRAIL

'SMART! You bet it's smart,' said Dick Anson, with enthusiasm. 'The cleverest trick I ever heard of. Each U-boat its own trailer.

'All right, Guy,' he went on, with a laugh. 'Don't get impatient. I'll explain. The dodge is this. The net we talked of is a mere gossamer arrangement made of the thinnest sort of steel piano wire. It's so light that the Hun never knows he has run into it. It doesn't offer any more resistance than a trail of seaweed.

'Fastened to it is this detector. It's a wooden arrangement, a sort of hollow spout crooked in the middle, and bigger at the end nearest the U-boat's stern. Being made of wood, it floats up to the surface. The pace at which it is towed through the water does the trick, and forces up that spout of water you see through the narrow top end.

Guy, who was staring fixedly at the little spout of white foam which Q17 was following across the calm surface of the North Sea, nodded gravely.

'Yes, I see,' he answered. 'I understand it quite clearly, Dick. And I'm free to admit it's an uncommonly smart idea. A simple one, too, and the only wonder is that no one ever thought of it before.'

'But this is what sticks me,' he went on. 'If you could set this net, why on earth couldn't you have put down a heavy one? One of the large mesh steel affairs, I mean, such as they have been using all along the coasts. Then you could have bagged the U-boat straight off, with everything in it, and Mr Ingram and Wallace would have been safe ashore this minute. Couldn't you have done that?'

'We could,' confessed Dick. 'Yes, we could have got a heavy net in time. But these are orders from the Admiralty. I'm going to let you into the secret, Guy. There can't be any harm in doing so now you're aboard here.

'The trouble is this. You know we have mined in the whole of the Heligoland Bight. We did it so thoroughly that we rather fancied we had hung up the pirates for good. But just lately the beggars have been coming out as freely as ever, and the Powers are more than a bit worried. When they got this detector arrangement, orders were sent out that the very first U-boat we could be certain of—like this one—we were to slip it on to her and follow her home. The idea is to find out what route she takes through the mine fields.'

'Follow her home!' exclaimed Guy, in dismay. 'How is that going to help us? Then the brutes will get Mr Ingram and Wallace and keep them.'

'No, they won't. Not much, Guy. Do you think we are going to be fools enough to waste a perfectly good U-boat? That's all arranged for, let me tell you. Your friend Vassall has seen to it.'

'Don't interrupt,' said Dick quickly. 'I'm going to tell you all about it. Of course, if there had been no prisoners in the U-boat we should simply have clapped a "mouldy" into her or strafed her with a depth charge. As it is, we have fixed up a rendezvous with a couple of our destroyers, and they will have a little trick for collaring her whole and unharmed.'

'What—right the other side of the minefields!' exclaimed Guy. 'What do you think the German fleet will be doing in the meantime?'

'Oh, we shan't be close enough to land to rouse them out,' Dick assured him. 'Besides, it will be night, Guy. It's going to take all of twenty-four hours to reach the spot. Don't you worry your head. It will be quite all right.'

'Glad to hear you say so,' replied Guy dryly. 'All the same, if you ask me, I wish to goodness you had chosen any other U-boat for this precious experiment.'

'Of course I'm funking it,' retorted Guy. 'Not for myself, but for the Ingrams. All the time I'm picturing them down below there, probably tied neck and crop, and wondering what on earth is going to happen to them. Besides, though you seem so sure this is all going to pan out according to plan, I'm not so certain about it. Suppose this U-boat doesn't go straight home, what then?'

'But she's bound to,' urged Dick. 'She won't go pottering about when she's got that neonite stuff aboard her.'

'I'm sure I hope she won't,' said Guy, rather bitterly. 'But if I had had anything to do with it, she would never have left Cleft Bay.'

'I suppose not,' replied Guy. 'All I can say is that I only hope things pan out right. I tell you straight that Mr Ingram is worth more to England than a fleet of U-boats.'

'If he's the only man who can handle neonite, he certainly is,' said Dick. 'I shan't forget the way it brought down that Hun plane and von Fromach. D'ye know, Guy, it seems to me that neonite would be just the stuff to slam into that Secret City place, if we could only get it there.'

'That's what I've thought all along,' agreed Guy. 'By the bye, Dick, what's happening about it?'

'Not a thing. That old footler, Karslake, has even gone so far as to warn my skipper here not to take any notice of what I say about it. He quite believes I dreamt the whole thing. They put me through the deuce of a medical before they appointed me to this ship. To say truth, I don't believe there's a soul in the country, barring you and the Ingrams, who has any belief in my story.'

'Oh, yes, there is,' Guy told him promptly. 'Vassall believes it. So does Stapylton.'

'That's the man,' said Guy, and told how he had given Stapylton a full account of the whole business.

'Stapylton's a good man,' said Dick thoughtfully. 'He's going up the tree at a great rate. He was a very junior sub when the war broke out, and now he owns the finest destroyer in the Service. I'm jolly glad he knows about it.'

'Vassall counts for as much or more,' said Guy. 'He don't say much about himself, but I fancy he's a pretty big bug in the Secret Service. He's going to tell Sir Rupert Dayle all about it.'

'Yes, but suppose we get mopped up in this show?' suggested Dick. 'It's on the cards, you know.'

'I fancy Vassall has taken precautions,' replied Guy. 'He's not the sort to leave it to chance.'

'Hadn't you better think of turning in, Hallam?' came a voice behind them, and, turning, Guy saw Vassall. 'It's quite likely you won't get a lot of sleep to-morrow night,' went on Vassall. 'Just as well to take a good nap now, while you can.'

'He's scared to go below because he thinks no one but himself can keep an eye on the U-boat,' jeered Dick. 'Mr Vassall is right, Guy. You'd better get a calk while you have the chance.'

'Perhaps you're right,' said Guy. 'But look here, you'll promise to call me if anything happens.'

'You bet!' replied Dick briefly, and Guy rather reluctantly left the cool, fresh, moonlit deck, and went down to the bunk allotted to him.

The submarine was running on her oil engines, and the row was abominable. But Guy was really tired after all his excitements, and very soon was as sound asleep as ever he had been in his life.

He had a most unpleasant dream to the effect that there had been a collision, and that he was sinking into the depths of the sea. Waking with a start, he found his head lower than his heels, and for the moment could not imagine what had happened.

Then he noticed that the roar of the oil engines had ceased, and had been replaced by a deep humming note, and he knew that the submarine must be diving.

'It's all right, sir,' said one of the men near by. 'Fritz is coming up to get a breath of air, so we're going down so as not to worry him. You turn in again, sir. We'll be on a level keel all right in a minute.'

He was right. In a very few moments Q17 had straightened out, and lulled by the humming of the great dynamos, Guy slept again.

'A fine morning, Hallam. We're on the surface again. Do you feel like going on deck for a sluice?'

'Jogging along just ahead of us,' replied Vassall, with a smile. 'She has submerged again. It's broad daylight, you know.'

Guy could see that for himself, for the sun was shining through the thick glass scuttle overhead. He followed Vassall on deck, and found the morning as clear and beautiful as the night had been.

Half a mile ahead, a small white spout of foam rising steadily above the calm surface indicated the position of the enemy. Far away to the north was a long trail of smoke smudging the horizon, and showing where a British destroyer was policing the sea which once was called the German Ocean.

'She has been behaving beautifully,' said Vassall, pointing to the spout ahead. 'She is making straight tracks for Hunland. Mostyn says she is a bit north of the usual course, but that no doubt is to dodge our mines. Now then, shall I use the bucket first, or will you?'

'Just as you like,' replied Guy, as he shed his borrowed pyjamas. Vassall filled the bucket.

The cool sea water was delicious, and as Vassall flung bucket after bucket over him, Guy felt the salt tingle of it in every vein. Then he did the same for Vassall, and after a good rub down with rough towels, the pair went below, more than ready for the fried bacon, toast, marmalade, and coffee which were ready for them.

Dick Anson was still in his bunk, but Mostyn breakfasted with them. Guy took the opportunity to say something about the Secret City. He wanted to see how Mostyn would take it.'

'Every word of it, sir. And if you had been there at the time he told it to Mr Ingram and myself, I think you would, too.'

'It's a queer business,' said Mostyn thoughtfully. 'But how do you account for the wreckage of Harman's ship being picked up in the Baltic?'

'Camouflage, sir. The Huns took it there and set it adrift,' replied Guy promptly.

'Just what they would do,' put in Vassall, in his quiet way. 'That is, if there really is a Secret City?'

'An Italian produced some odd results of the kind some years ago, and you know how clever the German is in developing an idea of that description.'

'Well, I won't commit myself one way or the other,' said Mostyn, as he finished his coffee. 'But, personally, I find the whole thing a hit beyond my powers of belief. Now I must go up. I'm a little puzzled at the way in which the U-boat is edging away northwards, and I want to get my bearings as clearly as I can.'

Guy might have enjoyed himself on board the submarine if he had not been so desperately anxious. There were a hundred things to see and learn aboard her, and it flattered him to find that all the crew accepted him as one of themselves. Every last one of them knew how he and Mr Ingram had got back on the U-boat that had shelled Claston. They were ready to show or explain anything Guy wanted to see.

Most of the time he spent on deck watching that curious little spout of white water travelling steadily on ahead. It seemed strange that the Germans were so absolutely unconscious of the trail they were leaving, but Dick explained that, when the U-boat rose to the surface, the detector tube trailed unnoticed in the wake. It was only while she was submerged that the spout showed.

As time went on, the course of the U-boat became more and more northerly. Mostyn was frankly puzzled, and so was Dick Anson.

'It doesn't look to me as if she could possibly be heading for Cuxhaven or Wilhelmshaven,' said the latter to Guy. 'She's running straight for Denmark.'

'But I thought she had to dodge to avoid our mine fields,' replied Guy. 'Isn't it possible that she will be striking in somewhere just south of the 56th parallel, and then working down through Danish territorial waters?'

'The course she's taking now will bring her up a long way north of 56,' said Dick. 'She's upsetting all our calculations.'

'No—oh, no! I don't think that for a minute, Guy. We have wireless, you know, and can call up help when we need it.'

Guy said no more for the moment, but he was not easy in his mind. The thought of the Ingrams was always upper-most. Apart from his fondness for them both, he realised more plainly than any one aboard the awful consequences that would ensue if the Germans once got hold of neonite.

As the day drew on, a slight haze began to cover the sky. It was still as fine as ever, and there was no wind, but the sun was hidden by a veil of soft cloud, and there was a sultry feel in the still air. Guy noticed that the wireless mast had been erected and that messages were flying.

The U-boat plugged along steadily, but her course was even more northerly than ever.

'So she is,' was Vassall's quiet answer. 'If you ask me, she's making for the Skagerrak. I believe she's going into the Baltic, and I shouldn't wonder if her destination is not the Secret City itself.'

CHAPTER XIV
IN THE STRAITS

'I do. I have thought it all along—ever since I heard that the U-boat was making north.'

'You're right,' he said forcibly. 'I'll bet anything you are right. It stands to reason that the Huns would take neonite and its inventor to the safest place they know of. What do you say, Guy?'

'I think as you do,' replied Guy. 'It's the most natural thing in the world. There's only one point which puzzles me. Why doesn't the U-boat go through the Kiel Canal? It would be a lot nearer.'

'U-boats are not using the canal,' said Dick quickly. 'We know that. It is packed with German shipping. And, in any case, the northern route would be the safer. It is not so heavily mined.

'Not much of a puzzle,' replied Vassall, with a smile. 'It was pretty plain from the beginning.'

'Will this make a difference?' asked Guy. 'I mean about meeting the destroyers and catching the U-boat.'

'Our range of wireless is not wide. And I don't quite like the look of the weather. It seems to me that thunder is brewing.'

'I've been thinking that this hour past,' Guy answered uneasily, 'But whatever happens, we musn't lose the Hun. If she gets away with Mr Ingram and the neonite, it would be a most awful business.'

'No, I have never seen the formula. But if I had the formula and was at Claston, I think I could do it.'

'Because I have the idea that Mr Ingram would have made a pretty good attempt to destroy the formula when he found how he had been tricked.'

'I'm certain he would. He has any amount of pluck. If he had had the chance I am certain he would have done it.'

'He is going to call up our destroyers at once. He says he won't risk Fritz getting into the Skagerrak or taking refuge in territorial waters.'

There were good grounds for Vassall's misgivings. The haze had thickened, and in the north-west the towering shapes of great cumulus clouds were piled high in the sky. Regular thunder heads, with white edges like packs of cotton wool. And although the sea below was still as calm as ever, there was wind above, for the great clouds were moving steadily up towards the zenith.

Meantime the U-boat kept steadily on her course. She was travelling at a good ten knots, and had so far showed no sign of wishing to come to the surface again. During the previous night she had thoroughly recharged her batteries, and was good for something like 150 miles of under-water travel. She would not be likely to put even her periscope up until nightfall.

It was now nearly four in the afternoon, and they had been travelling for about nineteen hours. During a large part of the night, when both vessels had been upon the surface, the speed had been fifteen knots, so now they were only about fifty miles off the mouth of the Skagerakk, and nearing the Little Fisher Bank.

'You bet,' replied Dick, and almost as he spoke there was a low growl of thunder, which came rumbling heavily across the calm sea.

'Can't say. The glass hasn't fallen much. It may be only a bit of a burst, and then over.'

'Yes. I don't think there's much risk of losing her. Anyhow, we know her course now, so we've only got to keep plugging along.'

'We are not going to let her get into the Straits. We shall collar her before then.'

Guy said no more, but all the same he was very uneasy. He stood straining his eyes for sight of the destroyers, but could see no sign of any craft whatever, barring the U-boat's steady spout.

A livid flash zig-zagged through the heart of the huge storm cloud, and less than a minute later thunder came booming through the quiet air. There was a sullen, heavy feel in the atmosphere.

Presently a puff of wind stirred the glassy sea. It was but a catspaw, and passed as it had come. But after it the crooked lightning gleamed again more venomously, and the thunder that followed sent a quiver through the stagnant sky.

A few huge drops of rain spattered the sea, and the darkness rapidly increased. It was lit by a sudden, tremendous blaze of electric fire, and now the thunder was like the crack of doom.

'Wind coming,' he said. 'Come below, and I'll lend you some oilies. We shan't be able to stand on the deck anyway. The sea breaks clean over it when there's any breeze.'

He led the way below, and provided Guy with a suit of stiff yellow oilies. When they came up again the scene had changed. It was blowing hard from the north-west, and rain was coming down in torrents. A short sea was rising and breaking in white foam over the body of Q17. Even in the conning-tower sheets of spray drove across them.

'I can,' Dick assured him. 'No need to worry, Guy. We can keep track of her. The only thing that troubles me is that we don't seem to get in touch with those destroyers.'

'They do, on special occasions,' replied Dick. 'But they have sweepers with them then.'

Before Guy could speak again there came a flash so white and blinding that both staggered. The very sky seemed to crack with the peal that followed.

'Hot stuff!' said Dick, recovering himself. 'This is more than I bargained for, Guy. Hope it isn't going to last, or we shall both be wishing that we could do a dive and stay snugly below until it was over. A submarine isn't what you might call a sea boat.'

A fresh blast of wind came shrieking across the sea. Guy clung to the rail, almost blinded with salt spray. Q17 was performing most curious antics, and though Guy had always rather fancied himself as a sailor, he was beginning to feel horrid qualms in the region of his third waistcoat button.

Dick wanted him to go below, but he flatly refused, and stuck to his post. The storm grew worse instead of better, and though only half-past five, it was almost as dark as night. The sea got up steadily, and the long, narrow steel hull pitched and rolled in an alarming fashion.

Seas began to sweep clean over the turret, and presently an order came from the skipper, 'Mr Hallam to go below.' So, much against his will, Guy had to go down.

It was worse inside than above, and what with the close air and the smell of oil, Guy had to fling himself flat on his back on his bunk, and lie there quite still. He felt miserably ill, but was somewhat comforted to see that more than one of the crew were affected in the same way. As for Vassall, he was deadly pale and dreadfully sick.

For more than two hours the infernal racket went on, and when at last the storm passed and the wind dropped, it was still raining heavily, while the horizon had shut down to less than a mile.

Mostyn let Guy go up again, and Guy had never breathed fresh air with greater relief. His first question was as to the whereabouts of the U-boat, and he was greatly relieved to hear that she was still in sight. When his eyes became accustomed to the gloom, he was able to see the spout of the detector, a wan patch against the leaden waves.

But there was no sign whatever of the destroyers, and Dick told him that they themselves were rapidly approaching the mouth of the Skagerakk.

'What are we going to do then?' questioned Guy, in great anxiety. 'Can we stop her single-handed?'

'I hope it won't come to that,' replied Dick gravely. 'It is all in Mostyn's hands, remember.'

Guy's spirits sank to zero. He felt inclined to curse the detector and its inventor, and the Admiralty who had ordered its trial. It would have been so easy to have captured the U-boat, whole and unharmed, in Cleft Bay. But it was no use grousing. All that was left to do was to keep a tight upper lip and carry on.

Carry on they did. By sunset they were in the mouth of the broad strait, still on the trail of the U-boat. The weather had improved considerably, and there was no sea to speak of. But clouds still covered the sky, and it was growing very dark.

Dick Anson, who had been below for a cup of tea and for a look at poor Vassall, who was really ill, came up again.

'Mostyn is going to carry on,' he said in a low voice. 'He means to follow her right into the Baltic.'

'Seems so, from what he said. He thinks that it's worth it. We may get some valuable information, and by charting our route in we ought to be able to get out all right. The worst place is the Sound, you know—just opposite Copenhagen. It's Danish territorial water, but the Huns have mined it just the same.'

Guy hardly heard the last words. He was thrilled with the idea that he might possibly set eyes upon this wonderful Secret City on Rosel, the very heart and centre of the hideous web spun by the Hun spider.

That the journey would be full of perils he knew full well, but even to these he hardly gave a thought. It seemed to him that at last his chance had come to see active service, and perhaps strike a blow for his country.

Navigation became ticklish. They knew they were among mine-fields, and had to follow dangerously near to their U-boat guide. Dangerously, as Dick explained to Guy, because she, with her mechanical ear, might hear her pursuer and endeavour to trick her. By this time they were far into the Strait, and knew that they had to depend upon themselves alone.

As night came on, the clouds blew away. But the moon was not up yet, and it was still extremely dark. It took two look-out men all their time to keep an eye on the guiding jet from the detector.

'Blessed if I know. I suppose we shall have to submerge. But it will be blind hookey with a vengeance among all these mine-fields.'

Another hour and still no sign of the U-boat. The sky was now clear as crystal and lit by a multitude of stars. The moon, however, was not yet up.

'She must have heard us,' said Dick at last. 'Otherwise she would have been up long ago. She can't stick it much longer, I'll vow. Her batteries must be pretty nearly run down.'

Guy strained his eyes through the night. But though his sight was good enough, he could see nothing. He had not been trained like these bluejackets.

CHAPTER XV
DODGING A DEPTH CHARGE

He glanced at the gun, which was already trained on the point where the periscope was showing.

'Fire the moment she comes up,' he ordered briefly. 'Try to get her on the water-line.'

Guy heard the words, and breathed a sigh of relief. At any rate, Mostyn did not mean to use a torpedo.

Now Guy suddenly saw the water boil almost dead ahead. Out of the swirl appeared a thick, dark object. It was the conning-tower of the U-boat. He found himself quivering with excitement. For the first time in his life he was to watch, indeed to take part in, a naval action.

There was not light enough to see Dick Anson's face. But he seemed as cool as possible, as he stood close by the gun. The shell was already in the breech, the block had snicked home, and the muzzle of the vicious-looking little weapon was trained straight on the U-boat.

The Hun seemed to Guy to rise very slowly. He saw the starlight gleam on her wet steel deck as it hove up out of the dark water.

The word had hardly passed his lips before a flash of fire spouted from the muzzle of the four-inch, and the crack of the discharge split the quiet night.

At the same instant another and brighter flash shot out against the steel side of the U-boat, and with it came the crash of the exploding shell.

'Good!' cried Dick. 'That's got him where he lives. Quick, men! Another before he gets his hatch off.'

The men needed no urging. The breech was flung open and another shell shot home. Before the U-boat was much more than awash, this second shell exploded almost on the same spot as the first.

'Holed her, by thunder!' said Dick. 'That'll do, sir, won't it?' he asked of Mostyn. 'We don't want to sink her.'

'Yes. That'll do,' called Mostyn from the turret. 'Stand by with rifles to let them have it if they try to show fight.'

He called an order down below, and Q17 shot off a sharp angle, ahead of the wounded U-boat.

As she did so Guy was conscious of something like a great fish flashing through the dark sea towards them.

'We've been looking out, my son,' replied Dick, with a grin. 'Lucky we did, too. I'm afraid your warning wouldn't have been much use if we hadn't changed course already. Watch her! Watch a Hun "mouldy" going to waste.'

There was not much to watch. The flash was gone almost before it had come, and all that Guy could realise was that the tin fish had gone some way astern of Q17, missing her by a matter of fifty feet or more.

'She may try one more,' said Dick, 'but I doubt it. If I'm not mistaken, she's got quite a lot of water in her already. I'd hate to be inside her. She must be getting horrid whiffy. Watch now, Guy. The next act is the white flag and "Kamerad" business.'

Mostyn may have been of the same opinion, but he was taking no chances. Q17 continued her quick circling movement. She would have been a difficult target to hit, even if the gentlemen aboard the U-boat had not been otherwise engaged.

'There! What did I tell you?' cried Dick, in triumph, as a something which gleamed pallid in the faint light of the rising moon showed above the U-boat's conning tower. 'The white flag, old lad! They've had enough. Salt water on their batteries, and a reek of chlorine fit to poison an ox. I only hope your pals will have sense enough to use wet handkerchiefs.'

'But it's all too easy,' gasped Guy. 'Two shells and one torpedo. Is that a naval battle?'

'Thrice armed is he who gets his blow in first,' he quoted. 'My good Guy, I've seen a perfectly good fifteen thousand ton battleship wiped out with one single "mouldy." And we got two shots into the Hun before she had a chance of a slap at us. It's all right, I assure you, and now all we have to do is to get alongside the pirate and help ourselves. Jove! I wish we could put a prize crew aboard and bring her home. But that's out of the question, I'm afraid. We're a bit too far from Blighty to try a game of that sort.'

'What's it matter?' Guy answered. 'We shall get the Ingrams back. Yes, and Cratch and von Fromach, too.'

By this time Q17 was within less than her own length of the U-boat. But Mostyn was still as careful as ever. Half a dozen of his men were ready with rifles, and his gun was still trained full on the enemy. If the Hun meditated treachery, Mostyn was ready for him.

'Come up on deck!' he shouted in German. 'One by one. And hands over your heads. Kindly remember that any of you who play the fool will be shot out of hand. Your commander first,' he finished.

A youngish German naval officer appeared. He looked decidedly crest-fallen, but had his hands well up according to orders.

'You have two British prisoners aboard,' said Mostyn. 'Be good enough to send them up at once.'

'All my men will have to come up at once,' replied von Metzger. 'We are in a sinking condition, and the gas fumes are very bad.'

'Then do as I request without delay,' snapped back Mostyn. 'The prisoners first, and the quicker they come the better for the rest of you.'

During the moment's pause that followed Guy's attention was suddenly attracted by a star that looked much bigger than the rest, and which seemed to be approaching them at great speed from a southerly direction.

'Infernal luck! It's the firing has brought her up. Five minutes more and it would have been all right. Get below, Anson. Fill the ballast tanks. We've got to do a quick dive this time.'

The destroyer was coming up behind the U-boat, and so far the crew of the latter had not noticed her. Guy felt the quiver of Q17 under his feet, and heard the water hissing into her tanks. But at the same time he saw the white head of Mr Ingram himself appear above the conning tower hatch of the U-boat.

Mr Ingram heard and clearly understood. Guy saw him turn and give a quick word to some one behind him. Then, with a quickness amazing for a man of his years, he was over the rail of the conning tower and into the sea. A second figure followed him. Both came swimming hard for the submarine.

Guy sprang forward to help. Q17 was sinking under his feet, but nothing would have induced him to take refuge below before he got the Ingrams aboard.

One after another, the men who had been on the deck of Q17 were darting down through the still open hatch.

And now the crew of the U-boat had realised what was happening. There were wild shouts for rifles. One man—Guy believed it was von Metzger—pulled a pistol and began blazing away. Guy heard a bullet smack heavily against the steel deck close beside him.

He heard some one shouting at him, but could not hear what was said. He was leaning right over, stretching out his arms towards Mr Ingram.

The old man swam vigorously. Next moment Guy had him, and by main force hauled him aboard.

The sea was actually ankle deep across the submarine's deck as Guy grasped the hand of the second swimmer. To his horror and amazement, it was the hand of a grown man, and it was a man's face, dark and sallow, and a head covered with intensely black hair that rose out of the water.

'I am Slavinski—a Czech—a friend,' panted the other in English. 'Let me come aboard. I have news for your captain.'

There was no time to talk. The bow of Q17 was already tilting downwards. Guy dragged the man up. 'Come on!' he cried, and made a dash for the conning-tower. He scrambled wildly up the short ladder, and simply flung himself through the hatch, tumbling right into the arms of the bluejacket who was in the act of closing the steel door.

'Can't wait,' snapped back the other, and his hand was on the lever when Slavinski took a flying leap in after Guy, and, missing his footing on the rungs of the ladder, fell heavily to the floor below.

Next instant the steel door clanged down. Only just in time, for the conning tower was so nearly under that the tip of a wave actually splashed through, soaking Guy and the bluejacket to the skin, and falling in a shower of spray into the interior of the ship.

At the same moment the bows dipped so steeply that the angle became that of a toboggan coasting down a steep hill, and Guy, unable to move either way, could only cling with both hands to the steel ladder and wait until she righted a little.

Down she rushed—down to a depth of seventy or eighty feet. Then she came back to an even keel, and, with her dynamos purring at full power, darted off like a frightened fish.

Guy swung quickly down to the floor below where the man who called himself Slavinski was lying all in a heap. As he stooped over him the bluejacket, whose name was Cray, followed him down.

'I don't know, sir,' Guy answered, in distress. 'I thought he was following you, and I waited. But when I got hold of what I thought was Wallace, I found it was this man.'

'Not that, at any rate, sir. So far as I could see, there was no one else in the water. He must have been left behind on the U-boat.'

Mr Ingram's face showed white and drawn under the glare of the powerful electrics. 'Then I have saved myself and left him in the hands of those fiends,' he groaned. 'But Heaven knows, I believed he was at my heels all the time.'

Before Guy could answer, the whole hull of Q17 quivered to the shock of a tremendous explosion. Guy staggered and almost fell, the lights went out, leaving everything in pitch darkness.

'A depth charge,' he said grimly. 'Now you knows what the U-boats feels when we gets after them.'

'Has it damaged us, I wonder.' Guy was surprised to find how calmly he was speaking.

'We'll have to wait to know that, sir. It's shook up our batteries some, anyway. But the engines is still running, so we ain't incapacitated, in a manner of speaking.'

Just then up flashed the lights again. Guy looked quickly round. If damage had been done, there was at any rate no sign of it. Q17 was still proceeding at her full submerged speed.

'I reckon she's all right, sir,' said Cray. 'I only hopes as the next won't be quite so near.'

'Ay, there's more to come. That there Hun destroyer, she's bound to do all she knows to get us. I reckon she'll have half the German fleet up afore morning. Nice job for them to find as we've got in here through all their mine fields.'

It sounded cheerful, but Guy had been so strung up already by the night's events, that he was neither alarmed nor even particularly excited. He was really far more disturbed about Wallace Ingram's fate than anything else.

Slavinski, who was still lying where he had fallen, stirred. He opened his eyes. They were large and dark, about as unlike those of the typical Hun as could well be imagined. His face, too, was refined and clever. Guy liked the look of him.

The man muttered something in a language of which Guy could make nothing, except that it was certainly not German. Then he put his hand to his head in a dazed way.

'My name is Slavinsky—Anton Slavinsky. I am a Czech,' answered the other, now speaking in good and correct English.

'I am grateful, indeed, to be in English hands,' he said, and there was no doubt in Guy's mind that he meant it.

'The boy who was with you, sir?' questioned Slavinski, fixing his bright eyes on the other. 'I have not seen him since I ran up on to the deck of the U-boat. I am sorry. I would have helped him if I could.'

'Then you left him down below in those stifling fumes?' said Mr Ingram accusingly.

'No, sir. I had nothing to do with it. One of the German sailors was bringing him up.

'I am sorry,' he added. 'Indeed, I am sorry, but for the moment I thought of nothing but the possibility of escape.'

'Because—' began Slavinski, and stopped short as the submarine quivered again in every plate and bolt, and the lights jumped violently.

'Farther off this time,' said Cray, with a satisfied air. 'The Cap'n has fooled 'em all right. They don't know what's come of us.'

'Because I am a friend of your country. Because I have been no better than a slave in Germany,' replied Slavinski, with sudden passion. 'Because the Prussian pigs have murdered my son. They forced him into their navy, and he was killed aboard the "Blucher" in the battle of the Dogger.'

'Then how do you come to be aboard one of their abominable pirate craft?' asked Mr Ingram.

'I am an electrician. I was pressed like the rest. I had to serve or be shot. I tell you I do not care for my life, but I wished to live in order that I might exact vengeance for the death of my boy.'

Slavinski choked and was silent. Guy felt desperately sorry for him. Even Mr Ingram seemed a little less suspicious. But the inventor was very bitter about losing his boy for the second time.

'He may be drowning this minute,' he said, biting his lip to fight down his emotion.

'I don't think so, sir,' Guy answered quickly. 'Indeed, I don't. I'm almost sure there was no one else in the water, and the U-boat would float until the destroyer took off her crew. Anyhow, if there is one person they would take care of it would be Wallace.'

'That brute, von Fromach, will wreak his disappointment upon him. The man is furious at failing to secure the secret of neonite.'

'What—hasn't he got it?' cried Guy. 'I thought you took the formula with you.'

'You think that I have let those treacherous dogs have the formula! Guy, you must be mad to dream of such a thing.'

'I took no risks. As soon as I realised that they meant treachery, I flung the envelope overboard. It was weighted and sank.'

'Much good that will do them!' replied the other, with contempt. 'Analysis won't help them.'

Guy drew a breath of relief. Anxious as he was about Wallace, it was a great thing to know that the composition of the terrible explosive was still a secret from the Hun.

'Hallo! Who is this?' Dick Anson had come up suddenly, and was staring at Slavinski.

'You may be right, Guy,' he said, 'but you can't get away from the fact that this man has been one of the crew of an enemy ship. He must be kept in safe custody until Commander Mostyn has seen him.'

'Perfectly,' replied Slavinski quietly. 'I am very willing that you should do as you see fit. All I will ask is that, when your captain is free, he will grant me an interview. I have information of value for him.'

'He certainly won't be able to see you for the present,' returned Dick, and, calling up a coxswain, put Slavinski in his charge.

'Might be worse,' he remarked dryly. 'At any rate the Hun seems to have lost track of us for the present.'

'It's moonlight, my son, and by this time the Strait will be fairly humming with Hun craft. Planes, too. No, we daren't show even the tip of our periscope for the present.'

There was a curious scraping sound as he spoke, a kind of metallic clink which came from outside the steel hull.

'That, Guy, is either a cable which they are using to drag for us, or else we've run foul of a mine. Sit tight. I must be off and see.'

CHAPTER XVI
NOSING HOME

THE moment the ominous sound was heard the engines had stopped. Through the whole, long, brilliantly-lit interior of the under-water ship an absolute silence reigned. Every soul aboard knew that they were in the most ghastly peril.

With a slight jar, Q17 settled on the bottom, and remained absolutely motionless.

'So far, so good,' said Dick. 'Since she hasn't been touched off already, there's always a chance.'

'Cut her loose,' replied Dick calmly, and as he spoke Mostyn's voice was heard calling to one of the "tiffies."

'Diving dress,' replied Dick briefly. 'No, we can't take you out. Probably Mostyn will go himself.

'Oh, it's simple enough!' he explained. 'At least, so far as getting out goes. These boats are of the Lake type. We have a diving chamber aft. Yes, there's Mostyn, and Perkins with him.'

Perkins, one of the artificers, carrying various tools, followed his captain through a small watertight steel door into the diving chamber. There was a pause while they got on their dresses, then a hissing sound was heard, as water began to fill the diving chamber.

'Got to go slow,' said Dick to Guy. 'Equalise the pressure, you know. Don't get worried. We're all right so far.'

'I'm not worried,' retorted Guy. All the same, he was feeling the strain. He, like every one else aboard Q17, knew perfectly well that the least sway of current or tide might bump the mine against the side of their vessel, and having studied the mechanism of contact mines, he was aware how slight a jar was sufficient to set one off.

The hissing sound ceased. There was a pause, then a heavy clumping sound on the turtle-back deck overhead.

'There they are,' said Dick. 'I wonder where she's hung up. In the rudder, most likely.'

'Fleuss dress,' explained Dick. 'Carry their own compressed air with them in a sort of knapsack. Oh, they're all right so far as that goes. But I must say I'd like to be outside with them and see what's going on.'

The heavy lead-soled boots of Mostyn and his assistant jarred overhead. That was all that those inside could hear. Otherwise, they were utterly ignorant of what was happening, or of how their companions were faring in their struggle with the hideous, silent enemy which they had encountered down in the black deeps.

To Guy the wait seemed endless. In his mind's eye he could see the two out there in the dark water, working with desperate caution to free their craft from the terrible danger into which she had run.

Even Dick Anson was feeling the strain. He was silent, listening eagerly to every sound that came from above.

Half an hour passed. Suddenly a slight quiver passed through the fabric of the submarine. Dick gave a sudden exclamation.

'That was the mine. They've cut the sinker away, and she's gone up to the top like a bottle. Jove, I only hope one of those beggarly Huns fouls her.'

There was a sudden hum of talk among the crew. Like Dick, they all knew what had happened, and felt an immense relief. A few moments later there were sounds in the diving chamber.

'All right!' he said presently. He gave a brief order to start the pump which cleared the diving chamber, and at the same time put over the lever closing the outer door.

Again a short pause; then the inner door was opened, and Mostyn and his man came out. Eager hands helped to unscrew their helmets.

'Yes. Her cable was jammed between the port horizontal rudder and the hull. The mine itself wasn't four feet above us.'

'About as close a call as the old hooker is ever likely to have,' he remarked. 'What did you do, sir?'

'Perkins cut the cable with a hack saw, while I fended off the beastly thing. But that's enough for one time, Anson. Get me some cocoa, like a good chap, and let's forget the episode as quickly as possible.'

'Right you are, sir,' replied Dick cheerily, and was off to procure the necessary refreshment.

Mostyn drank it as if he needed it. Indeed, the water had been cold enough in all conscience, and the strain a very heavy one. While he drank, Dick told him about Slavinski.

'Bring him here into my cabin,' he said. 'Vassall and I will examine the gentleman, and see what he has to say for himself. Meantime, you can start up again. Keep her going steadily on the chart course. After a bit I shall venture up and have a look round.'

Dick gave the necessary orders, then went forward to where Slavinski was confined, and himself brought him to the tiny cabin aft, where Mostyn was waiting. Vassall, still looking very seedy, joined them.

'I'm inclined to believe he is,' said Dick. 'Anyhow, Mostyn will find out. He's a nailer at that sort of thing.'

'Anson,' said Mostyn. 'I believe I have to apologize to you. This man has been telling me exactly the same story that you brought home.'

'Well, sir,' said Dick quickly, 'all that I can say is that I hope you will let him tell his story to Captain Karslake.'

'I think I can promise you that. Always supposing that we ever see that gentleman again.'

'I mean we are in a tight place, Anson. The Huns will scour sea and sky for us. They know we have Ingram aboard. Besides that, we have dodged through their mine-fields. It's going to be awkward for them if we get clear.'

'Go up and have a look round. We are getting near Anholt Island. That's Danish, you know. What we have got to do is to get back round the Skaw before daylight.'

'Why go up, sir? We can carry on under water, and it isn't as if we were pinched for room.'

'You forget the mine-fields. And in all this dodging we have been doing I am clean out of my reckoning.'

The tanks were partly emptied, the hydroplanes cocked, and Q17 quested slowly upwards. Mostyn, seated at the periscope table, watched anxiously.

Mostyn studied the little picture shown on the screen below him. It showed only a circle of small waves, the tips of which gleamed silver in the pale moonlight.

'Wish I could spot that blessed island!' murmured Mostyn. Then all of a sudden he stiffened.

Again there was an anxious wait. At any moment might come the thud of a depth charge. But nothing happened, and Mostyn resolved to rise again.

Very cautiously the periscope was poked up. At first the sea in the camera's circle seemed perfectly empty. Then, as Mostyn watched, a sudden gleam shone in his eyes.

'There she is, questing round, but clean off the track. She's alone, too, Anson. 'Pon my soul, I've a mind to have a slam at her.'

'Stand by the tubes,' rang out his order. But the men, scenting a chance, were already at their stations.

There was a moment of tense silence. Guy, watching Mostyn's upraised hand, could hardly breathe for excitement.

The seconds ticked by. Mostyn's eyes were fixed upon the moving picture before him.

There came a low hissing sound as the torpedo left the tube, then the gurgle of water into the compensation tank. The bow of Q17 lifted slightly.

'Again!' ordered Mostyn, and a second of the long steel fish was slipped on her deadly errand.

'Got her! The first has got her!' yelled Dick Anson, and as he spoke the submarine shuddered like a live thing.

'Look!' cried Dick, and Guy, peering over his shoulder at the picture on the screen, saw a huge crimson flame shoot up against the night sky. Beneath it was a vast column of water, and half hidden in the fountain of spray, a long dark ship was tossed upwards, seemingly in two pieces.

The column fell, the glare died, and in a welter of smoke and foam the two halves of the Hun destroyer rolled over and sank out of sight.

Q17 rose like a porpoise, and ran awash towards the whirlpool in which the enemy had disappeared.

She had not covered half the distance before Guy, who was still gazing eagerly at the periscope picture, caught a faint glow of light to starboard.

'Land. Anholt lighthouse,' Mostyn answered. 'That's a bit of luck. We know where we are now. And, by James, we're in territorial waters, too. Well, that's not our fault, and Fritz deserves what he's got for chasing us within the limit.'

'Hallo!' he broke off, as a fresh beam, and a much more brilliant one, suddenly lit the site of the wreck, turning the tumbled waters to silver. 'Down you go! Sharp, for any sake! Here's another of the beggars almost on top of us.'

Q17 slithered forward and shot steeply into the depths. As she went there the thud of a gun came faintly through her steel hide, to be followed almost instantly by the shock of a shell exploding just aft.

'Close enough!' growled Mostyn. 'However, a miss is as good as a mile, and she's not so close but we can puzzle her.

'Hard over with the rudder,' he ordered. 'And, Hallam, tell that man Slavinski I want him.'

Slavinski did so unhesitatingly, and Mostyn at once gave orders which would take Q17 into it.

'We are making south again,' he explained. 'I am going right round the island on the western side. That will puzzle them if anything does.'

As he spoke, there came the now familiar thud of a depth charge, but the explosion was so distant it barely shook them.

Mostyn laughed softly. 'I knew we could fool them,' he said. 'We've done it, too. Now I think we can make tracks for the Skaw.'

'As for you,' he said to Guy, 'the best thing you can do is to get a cup of cocoa and turn in. You're new to these games, and they take it out of a man.'

Guy had to confess to himself that he was feeling the strain, and that the skipper's advice was good. He brewed himself a cup of cocoa over the electric stove, slipped off to the corner where he bunked, and in spite of all the excitements of the night, was soon sound asleep.

There was no daylight to wake him, yet when he glanced at his wrist watch he saw that it was nearly eight, so that the sun must be a long way above the horizon.

Dick Anson stood beside him. 'Get up, you lazy beggar!' he laughed. 'You can have just enough water to sponge your face with, then you'd best hurry for breakfast. By the savoury smell the cook must be opening a tin of sausages.'

'Ab-so-lute-ly nothing. Just been plugging along all night. Thanks to your friend Slavinski, who seems to know these waters like the palm of his hand, we haven't sniffed another mine. Now we're well out in the Skagerakk, and the skipper talks of going topside pretty soon.'

'That's good,' said Guy. 'Can't say I fancy this potted air. I've got a head on me like a sofa cushion.'

The tinned sausages were as good as they smelt, and the coffee, hot and strong, cleared Guy's head. All the same, he looked forward eagerly to a sniff of real fresh air.

This was not long in coming. About nine Mostyn gave the order to rise, and Q17 thrust her periscope above a multitude of little white crested waves which flashed under a bright and almost cloudless sky.

To every one's great relief, no enemy was in sight, and Mostyn gave orders to run awash and open up.

The sweet, cool air of the North Sea was delicious after the long hours pent in the closed interior of the submarine, and Guy drew deep breaths as he got his head above the hatch.

'You can get out on deck if you like,' said Dick Anson, 'but keep an eye lifting for aircraft. Just remember we're a long way still from our happy home.'

Guy nodded, and dropped down on to the turtle back. Here Mr Ingram joined him. The inventor was looking very white and worn, and Guy, knowing how deep was his anxiety on his boy's behalf, was very sorry for him.

'That man Slavinski tells me the U-boat was bound for this so-called Secret City,' said Mr Ingram. 'I am wondering if they will take Wallace there.'

'How can we possibly do so?' demanded the other bitterly. 'Even the British Navy can't get into the Baltic.'

'But a submarine can,' Guy answered. 'We were well on our way there last night.'

'That might be possible,' he said slowly. 'Yes, it is on the cards. But do you suppose that the Admiralty will sanction any such expedition? They told young Anson he was dreaming when he spoke of the place.'

'Ah, but we have Slavinski now to back him. And don't forget that Stapylton, too, believes in Dick. Stapylton is a friend of Admiral Dayle.'

'You need have no fear. Every attempt will be made to smash up this place on Rosel, Mr Ingram,' said a voice behind them, and, turning, Guy saw Vassall.

The Secret Service man was still looking wretchedly ill, but he made no complaint of what he had been through.

'I have been talking to Slavinski,' he went on, 'and as soon as we land I propose to take the man to London.'

'I don't think. I know,' replied Vassall quietly. 'The man has given me definite proofs of the truth of his story. What is more, it exactly corresponds with what young Anson has told me already. With his help—and with yours, Mr Ingram—I believe that we can make a successful attack upon the place. You may, at any rate, take it from me that it will be tried.'

'But if it is tried,' he said. 'If it is tried, and if my son were there, what chance would there be for him? You know the effects of neonite.'

'Besides, there are other ways,' he added presently. 'You may rest assured, Mr Ingram, that everything that can be done on behalf of your son will be done. More I cannot say at present.'

'Fat lot of use you people are as scouts. Every Zepp in Hunland might have been overhead for all you'd have known. However, Fritz seems to have chucked in his hand.'

'What do you mean?' asked Guy, looking hard at Dick. 'You've got something up your sleeve.'

'Well, we've just got a wireless to the effect that one of our light squadrons is doing a sweep in this direction. With any luck, we'll meet 'em in an hour's time. So on this occasion there's quite a good chance we may see our happy homes before we're much older.'

CHAPTER XVII
A MORNING CALL

'YOU really mean to tell me that you believe in this cock and bull story, Admiral Dayle?'

The speaker was Captain Karslake, and the scene was the same spacious and high-ceilinged room in which Dick Anson had had his previous interview with the elderly captain.

Admiral Sir Rupert Dayle regarded Karslake with an indulgent smile. The Admiral was a tall, handsome man of just over fifty. Though the hair was silver over his ears, his complexion was as fresh as that of a boy of twenty, and his sea-blue eyes were as keen and full of life as ever they had been.

'Yes, Captain Karslake,' he answered, 'strange as it may seem to you, I do believe it. And I think that, apart from the corroboration which this man Slavinski has provided, I should have believed Lieutenant Anson from the beginning. The fact is that his story is a little too strange to have been invented. Also, if you knew the Hun mind as I flatter myself I do, you would realise that the whole business fits in. This Secret City is just the sort of thing which appeals to the German. As a matter of fact, I have even heard whispers of it for some time past.'

'Even if there is any truth in it, we can do nothing,' he said. 'Now that Russia is a mere German colony, the Baltic is a closed sea to us.'

'How about Q17?' suggested the Admiral dryly. 'She seems to have been well on her way there.'

'That is true. But if she had followed her leader a little farther, she would undoubtedly have done so.'

'And suppose she had, what earthly good could she have done against a fortified place like this Rosel Island?'

'Not much, I will admit. But supposing she had had shells loaded with this new explosive, neonite, even a comparatively small craft of her type might have done great things.'

'That shows how much attention you pay to the new inventions, Karslake,' returned the Admiral. 'Mr Ingram, the inventor, tells me that he submitted it many weeks ago.'

'Good Heavens, you don't expect me to wade through all the crack-brained schemes that every lunatic in England flings at me with each post!' exclaimed Karslake.

'I take it that it is your duty to winnow the chaff so that you may get at the wheat,' answered Dayle rather coldly. 'We need every brain in England to beat the Hun, and thank goodness we have some good brains in the country. This neonite, for instance, seems to me to be an epoch-making invention.'

'Yes. So new that it puts everything else out of date. It is what turpinite originally pretended to be. Do you mean to say that you have not heard of how Mr Ingram and his assistant, a boy named Hallam, destroyed the U-boat which attacked the works at Claston?'

'Yes, I did hear of that,' he admitted. 'I was going to inquire into the matter. I have asked for reports.'

'I had them all days ago,' replied the Admiral quietly. 'The facts show that Ingram used an electric gun of his own invention, and one—one only of these neonite shells. By Hallam's account brought to me by Vassall, the shell did not actually strike the U-boat, yet the resulting explosion destroyed her as completely as a full hit with a twelve-inch. Divers who have been at work in Galleon Gap say that the whole fabric of the craft is split from end to end in the most amazing fashion.'

'I could not have better. I am completely satisfied that in this new explosive we have an invention which will destroy the military power of Germany.'

'We must have it in the Navy,' said Karslake. 'That is, if it can be used in ordinary guns.'

'Whether it can or not we must have it at once,' replied the Admiral quickly. 'But we are wandering from our subject. Its first use must be to destroy this stronghold on Rosel. If the Germans get their Cold Ray to work on the Western Front, no gun or explosive can save us.'

'But you cannot get it there,' objected Karslake. 'A submarine cannot carry this electric gun, which no doubt needs a very considerable horse-power to propel the shell.'

'Yes,' said Dayle firmly. 'I admit the risk, but she is the only ship fit for this particular task, and I am convinced that she could not be better employed. I propose, if the consent of my colleagues is given, to fit her out at once, and to let her start at the earliest possible moment.'

'It seems to me a mad scheme,' he said. 'Personally, I should have reserved her for the task for which she was originally planned. Still, I am not going to object, although I am convinced that if one does reach the Baltic, we shall never see her again.'

'I don't bet,' replied Karslake. 'But I will tell you what I will do. If this thing comes off, I will stand you and the neonite man and all the survivors as good a dinner as rations allow. Will that suit you?'

In a smaller room across the passage three people were awaiting the Admiral. They were Mr Ingram, Guy Hallam, and Vassall.

'You need not look so anxious, Hallam,' said the latter pleasantly. 'I think I can promise you another trip to the Baltic.'

Guy's eyes shone. Mr Ingram raised his head. He was looking terribly thin and worn.

'And you, Mr Ingram,' said the Admiral kindly. 'Are you feeling able to do a deal of hard work?'

'Sir,' said the inventor, 'I will do anything to destroy the German, and to recover my son.'

'I thought you would say so. But remember this—that we depend upon you more than any other individual for the success of our enterprise. You must take care of your health for all our sakes.'

'Don't worry, Admiral. I shall last until I have done my work. Tell me what it is.'

The Admiral took a chair and began to talk. The others listened eagerly. Even Vassall, a man who had seen and done so much that he was not easily excited, sat as still as a statue, with his eyes fixed upon the speaker.

'I am not going to give you details of the vessel known as X1,' said the Admiral presently. 'Even you, Mr Vassall, do not, I fancy, know more than the fact that she exists. I will merely say that she is a submersible cruiser of a size and power very much greater than anything that even the Germans have yet attempted. She is, in fact, a submarine warship of large displacement, heavily armed, with a surface speed of 25 knots, and even with her present armament, perfectly capable of engaging any light cruiser afloat.

'Now what I want to know, Mr Ingram, is this. How long will it take you to mount one of your electric guns in this ship?'

'The whole resources of every dockyard in the kingdom shall be at your disposal,' the Admiral assured him.

'You need not leave London. You can do all your ordering by telegram. I or my secretary will be at your elbow all day and every day. In a case like this time is everything, and money no object.'

'Sir,' he said, 'you have given me the chance I have been praying for for years. I give you my word you shall never regret it. And now to business!'

'I left my two men in charge, sir—Tyrrell and Whitworth. They are both thoroughly dependable.'

'I am glad of that. At the same time, the place is a lonely one, and there is always a certain risk. This country, as you know, still teems with Germans. I suggest that Hallam here should go up at once and take charge. No doubt there is much that he can do there.'

'It is a good suggestion,' said Mr Ingram. 'He will then be able to supervise the preparation of neonite sufficient for our purposes.'

He glanced at his watch. 'If he goes at once he will catch the evening train from King's Cross.'

'He shall go to the station in my car. It is waiting outside,' As the Admiral spoke he touched a bell. An orderly appeared, and the Admiral gave directions about the car.

Vassall, who up to now had been merely listening, stepped up and said something to the Admiral in a low voice.

'Capital! You will go with him. I shall feel safer in that case, and I dare say Hallam will, too.'

'He is,' replied the Admiral. 'You two had better start at once. Have you money?'

'Well, you know where to draw more when you need it,' said the Admiral, offering his hand to the Secret Service man.

'Remember, Hallam,' he said, 'that this is your chance. From all I hear, you have done very well up to the present. But now you are going to be tested in earnest.'

'Just this, sir,' said Guy, speaking with an effort. 'I wanted to ask you if—if—I really am going on this expedition?'

'Of course you are, my boy. And if it succeeds and you come safe out of it, why, anything I can do for you shall be done.'

A couple of minutes later, the two were in the car, and whirling through the traffic of Parliament Street.

'I'll make you a small bet that I know what you are going to ask for,' he said. 'It will be a commission in His Majesty's Navy.'

Vassall was an old hand at travelling, and knew everybody, from station-masters to guards. Consequently, Guy had a most comfortable journey, and was able to sleep a good deal of the way. They arrived at the junction at an early hour next morning, had a cup of coffee at the local hotel, then hurried out to Claston in a hired car. By himself, Guy could not have got a car for love or money, but Vassall seemed to be able to open every door.

It was only five days since Guy had left Claston. But so much had happened since that it seemed quite strange to set eyes again on the square, solid-looking house by the sea, and the workshops beyond it.'

'Pity we did not wire your housekeeper,' said Vassall, as the car topped the slope and began to slide down towards the house. 'She would have had some breakfast ready for us.'

'You needn't worry,' replied Guy, with a smile. 'Hannah won't waste much time in getting hot coffee for us. And we still have some home-cured ham, and there are plenty of eggs.'

'Funny!' he said. 'There's no smoke from the kitchen chimney, and the windows are still closed.'

'I think we will proceed on foot,' replied the Secret Service man. 'There may be nothing wrong, but it is always as well to be on the safe side. By the bye, are you armed?'

'Good! There is nothing better. Now, tell me, can we get at the house from the back, without being seen?'

'Yes. See that wall—the one of dry stones? We can get behind that and creep right up under the sunk fence which runs at the bottom of the kitchen garden. Then we can sneak up between the gooseberry bushes.

'I can't say. But you admit yourself that there ought to be smoke, and the windows should be open. Of course, your housekeeper may be ill, or away—'

'She's never ill, and she would not dream of leaving the place while her master was absent,' cut in Guy.

'Then it seems to me that something must be amiss,' said Vassall, in his quietest tone. 'Remember that, even if Cratch or Steubel is back in Hunland, he still has his agents on this side. You and I collected several that day they attacked the car, but I don't flatter myself that I made a clean sweep. On the whole, I think we will go up quietly. Lead the way, Hallam.'

It was a simple matter enough to creep up behind the wall and gain the sunk fence below the garden. As they neared the house Guy was uncomfortably struck by the silence that hung over the place. Ordinarily speaking, Hannah would have been bustling in and out, opening doors, shaking mats and so on, while Tyrrell, who was a cheery person, would almost certainly have been whistling over his work.

As it was, there was not a sign of life or movement. The place might have been absolutely empty and deserted.

'Go slow through the bushes,' whispered Vassall. 'Whatever you do, don't let any one see you from the house.'

'It's quite possible to see under a blind,' said Vassall dryly. 'Wait. I will go first.'

He crawled up among the bushes. Guy was struck by the amazing silence and caution with which he moved, and did his best to copy him. Beyond the gooseberries were some wind-swept shrubs growing close up to the side of the house. Vassall got among these, and crawled to the very wall. Guy came close behind him.

'Now comes the tug-of-war,' whispered Vassall. 'How can we get in without being seen?'

'The pantry window,' Guy answered, in an equally low tone. 'The catch is broken. I know it, for I have climbed in that way before now.'

By this time Guy was thoroughly strung up. He was in more than a bit of a fright, too. The idea that spies might be actually in possession of the place was not a pleasant one. Supposing they had got at the safe and the formula of neonite locked up there?

The pantry window was partly hidden by the shrubbery. Guy reached up and tried the sash. To his joy, it yielded at once. He pushed it open and slipped into the little room. Vassall followed.

Vassall raised his hand for silence, and they both listened. Barring the murmur of the waves at the base of the cliff a hundred yards away, there was not a sound.

Guy was now certain that something was seriously amiss. He was not surprised to see that Vassall had his pistol ready in his hand. The Secret Service man pointed to the door. Guy nodded and, tip-toeing forward, unlatched it very softly.

It opened into the back passage, and just opposite was the door of the kitchen. There was no one in the passage, and the kitchen door was just ajar.

Guy bit off the exclamation that rose to his lips. The first thing he saw was poor, stout Hannah tied tightly with a long coil of rope into a kitchen chair. She had been brutally gagged with a dirty dish-cloth, and her lips were quite blue. Her head lolled over sideways. She had either fainted or was dead.

Vassall checked him with a sharp gesture, and, moving quietly to the chair, removed the gag from Hannah's mouth.

'In Mr Ingram's room behind the sitting-room. You go through the passage door, and it is the first door on the left.'

Guy slipped off his boots in a moment. Vassall's were shod with rubber, and he did not remove them. Silent as two ghosts, they moved up the passage. The sun was shining brightly through a window to the right. It struck Guy as the strangest thing to be hunting burglars in broad daylight.

Vassall got the door open without a sound. He stood in the hall with hand upraised, listening keenly.

Now Guy did hear something. It was the soft scrape of a drill on metal, but the sound was very slight. Evidently oil was being used in plenty.

The door of Mr Ingram's room was closed. Guy saw Vassall frowning as he looked at it, and realised his trouble. The click of the latch as they opened it was bound to attract the attention of those within, and to put them on their guard.

'There's another door from the sitting-room. If I were to go round and rattle the handle you could burst in this way.'

'Excellent!' he whispered back. 'You can open the door, but mind that you keep behind it. This sort shoots at sight.'

'Right!' said Guy, and slipped away. As luck had it, the sitting-room door was ajar, and he entered without a sound. So far as a quick glance showed him, nothing had been meddled with in this room.

He reached the door and paused an instant. The scraping of the drill still continued. Holding his pistol firmly in his right hand, he grasped the handle of the door with his left, then, turning it sharply, stepped quickly back behind it.

From inside the room came a harsh exclamation. There was a sound of a man springing to his feet, and at the same instant the vicious report of an automatic. The bullet crashed through the woodwork of the door just on a level with Guy's heart, sending splinters in a shower into the sitting-room beyond. So quick and accurate was the shot that if Guy had not been under shelter of the wall he would most certainly have been killed.

Like an echo came a second shot from the other side. There was a smothered gasp, the sound of a heavy fall.

CHAPTER XVIII
POISON GAS

GUY could not restrain himself any longer. He stepped out from his shelter and looked into the room.

The safe, a very heavy one, was let into the opposite wall. In front of it a man lay flat on his face on the floor. His body twitched slightly, but Guy realised instantly that he was either dead or dying.

He barely glanced at this man. It was the other who claimed his attention. A great, scowling brute with the chest of a Hercules and the wickedest eyes that Guy had ever seen in a human face. He stood facing Vassall, who was in the opening to the left, and the savage malignity of his gaze sent cold chills coursing down Guy's spine.

'Hands up!' said Vassall again. His automatic was levelled full at the other's head. 'At once, or I save the hangman a job.'

Up shot the man's hands, but the right was clenched, and in it Guy caught a glimpse of some round object, about the size of a fives' ball.

The crack of Vassall's automatic sounded like thunder in that narrow space. The man's right arm snapped like a broken stick, and he shrieked with pain as it dropped, useless, to his side. The bulb which he had been holding tinkled to the floor and broke.

As he spoke the spy leaped clear and made a dash at Vassall. As he came he used his left hand to snatch from his pocket a second of the little shining globes.

The spy's left hand was uplifted. Guy saw that in another second the deadly little missile would be flung full in Vassall's face. There was no time to lose. Raising his pistol he took a snap shot at the man.

The bullet seemed to take him in the side under his uplifted arm. Down he went with a tremendous crash, the glass ball smashing as he fell.

Already Guy was conscious of a sweet, sickly odour. His head was spinning. He turned and made a blind rush for the door. He got outside, flung open the hall door, and, stumbling on to the grass outside, fell in a heap on the turf.

For a moment he felt very bad indeed, but he did not lose consciousness. Then Vassall was beside him, bending over him.

'Some ethyl compound, I fancy. I don't know. But if you had had one good whiff of it, it would have finished you.

'You did well, Hallam,' he said decidedly. 'That was a clever shot of yours. It saved me. My pistol, for some unearthly reason, had jammed.'

'Dead as a stone. But even if you hadn't, the gas would have finished him. See here. There may be a third man. I must go and see. You lie here. You couldn't have a better place. Whatever you do, don't go into the house.'

'I'll see to her as soon as I have had a look round. But if there was a third spy, I'm afraid he has taken to his heels. The firing would have warned him.'

He pointed across the garden. Below the sunk fence a man's head had appeared for an instant, then vanished again.

Guy tried to follow, but he was still dizzy, and could not run. He stood and watched the chase.

Vassall went leaping through cabbages and over potato rows at a wonderful pace, but before he reached the top of the sunk fence the fugitive had gained the stone wall. As he flung himself over it, Vassall stopped and fired.

It was a long shot for a pistol, but the howl of pain that followed was proof of a hit. The man, however, was still able to run. He got over the wall, and disappeared on the far side.

Vassall leaped down the sunk fence and tore along on the near side of the wall. He ran fifty yards at full speed, then suddenly pulled up.

Guy saw him lean across the wall, and this time two shots rang out almost simultaneously. Vassall's hat flew from his head, but from the far side of the wall came a piercing scream.

A couple of minutes later he re-appeared, and walked briskly back. There was a grim smile on his face.

'Bagged the bunch,' he said briefly, as he came up to Guy. 'Yes, the third is finished. I rather wish he wasn't, for I might have got something out of him. Now what about the old lady?'

'And the men?' added Guy seriously, as he started round to the back of the house.

The door of the kitchen being closed, the gas had not invaded that part of the house, yet even so its sickly odour was plain. To Guy's great relief, poor Hannah had come to herself, but she had nearly been scared into a second faint by the firing.

Guy snatched up a knife and cut her loose as quickly as possible. Then he and Vassall between them got her outside.

'It's all right, Hannah,' Guy assured her. 'We have finished up the whole lot of the ruffians. Now are you well enough to tell us where Tyrrell and Whitworth are?'

'I don't know no more than you, Mr Guy,' replied Hannah, struggling between faintness and indignation. 'I'd no more than got down to the kitchen when one of them nasty brutes jumped out from behind the press and threw a cloth over my head and nearly choked me. Then they tied me up as you saw, and the gag near suffocated me. Nice goings on, I must say! What's the country coming to?'

'We must leave you here for a few minutes while we look for the men,' he said. 'Don't go into the house, for there is poison gas in it. You may feel quite safe. All the three men who attacked you are dead.'

'The men sleep over the workshop,' Guy told Vassall, as he led the way quickly to the other building. 'I only hope they have not murdered them.'

Vassall did not reply, but there was a very anxious look on his face as he followed Guy into the workshop. This was a large place, one end lighted from above. The other part had an attic over it to which a ladder stairway led.

There was no sign of the men below. Guy went up the ladder with a speed that surprised Vassall. Vassall saw him stop at the top and heard him gasp.

It was an ugly sight that met their eyes. Poor Tyrrell, who was a slightly-built man of about forty, lay on his back on the floor, with his arms stretched out. His eyes were closed, and blood dabbled his face and hair.

Guy flung himself down beside Tyrrell, while Vassall hunted round for Whitworth. He found him lying on the far side of his bed in much the same case as Tyrrell, only he, it seemed, had been struck down with a sand-bag, for there was no wound.

He was insensible but not dead, and Guy found that Tyrrell's heart was still beating.

The next hour was a busy one. The first thing was to attend to the two men, and Guy soon found that Vassall was as good as a doctor. He knew exactly what to do, and how to do it, and Hannah, too, rose nobly to the occasion. By ten o'clock Whitworth and Tyrrell were both as comfortable as they could be made, but neither was yet able to tell what had happened.

'Hallam, you had better take the car and go for the police,' said Vassall. 'They'll take these dead bodies off our hands. Oh, and you had best fetch a doctor too. Not that he can do much good.'

'You'll have some breakfast, Mr Guy, before you take a step off this place,' declared Hannah firmly.

So in the middle of the morning the two sat down to the long-delayed bacon and eggs. They ate in the kitchen, for the rest of the house still reeked of the filthy compound which had filled the shells, and Vassall would not allow any one into the room where the two spies still lay as they had fallen.

Guy was not sorry to get away, even for a little while. The events of the morning had shaken him up. It was the first time in his life that he had ever shot a man dead at close quarters.

He wasted no time in reaching Brocklesby, and after sending a wire to Mr Ingram in London, drove to the Police Station and told his story to an amazed inspector.

The latter, with another constable and a surgeon, came back with Guy in the car to Claston. Vassall told the inspector to take away the bodies and keep them for the inquest. It rather startled Guy to hear Vassall issue his orders as if he were Chief Constable of the Riding. He had hardly yet realised what a very big gun was the Secret Service man.

The safe had not been opened, so the papers were right enough. But it gave Guy cold chills to think how very near he and Vassall had come to being too late.

'We'll take no more risks,' said Vassall, in his decided way. 'I'll have a couple of my own men down here to-morrow, and I'll send for four fresh workmen, and a nurse for Whitworth and Tyrrell. The inspector will take my messages in.'

He wrote them at once, handed them over, then when the police had gone in a large car which had been sent out for them, he turned to Guy.

'We have done enough for one day, Hallam. I'm going to ask you to show me round the works, then I think we will both have a nap till tea-time. There are strenuous days ahead, and we must keep ourselves fit for the work before us.'

It was wonderful to Guy to see the ease with which Vassall understood all that he saw. The electric gun had no problems for him. He knew all about the Bachellier electric railway, from which Mr Ingram had got hold of his original idea.

It was a warm day, and afterwards they went down to the beach and lay on the sand and drowsed. Guy had a swim in the sea; then they went back to tea.

By this time Tyrrell was conscious, but he could tell little more about the attack then Hannah had been able to.

The spies had gained their bedroom while they were both still asleep. He had jumped up, only to be bowled over at once by a blow from a heavy, knobbed stick. He was delighted to hear of the fate of the gang, and still more to know that the electric gun was going to be used.

'I tell you, sir,' he said to Guy, speaking very earnestly. 'I'd give a hand to help in the show. It 'ud be worth it to see what neonite could do in real battle. I've never been sorrier than that I was away that day you and Mr Ingram strafed the U-boat.'

'You get well quick, and help us turn out neonite shells,' Guy told him. 'That's our job for the present.'

Next day Vassall's men turned up, and under Guy's supervision the manufacture of neonite began in earnest. Every one was keen as mustard. Even Vassall insisted on helping. The business was simple enough except for the production of the rare element which was what gave to the explosive its peculiar and terrible power. This Guy did himself, with only one assistant, a young chemist named Grange, who had come down from London with the rest.

The two worked from morning until night. If Vassall had not been there Guy would hardly have left the laboratory. But Vassall very wisely insisted on a walk and a swim each day, and this kept Guy fit.

Not a soul from outside was allowed to approach the place, and it gave Guy a curious sense of the enormous importance of his task to see a destroyer on special patrol outside the bay. Her task was no light one either, for on two nights a U-boat made an attempt to enter the Gap, clearly with the idea of putting in a shell or two and bolting.

One did bolt; the other, caught in a detector net, was followed and destroyed with a depth charge.

News came from Mr Ingram that he, too, was up to his eyes in work. He had seen X1, and though he did not trust any details to paper, yet from what he did say Guy gathered that he was not disappointed. A new gun was being made under his supervision, and would be adapted for carrying in the submersible.

'The way the men work is wonderful,' he wrote. 'We have no fewer than four shifts, six hours each, so the work goes on night and day, and even I can hardly credit the pace at which it is being done. I hope that up at Claston you are getting on as rapidly.'

Guy was able to assure him that they were. The enormous influence of Admiral Dayle was making itself felt in every direction. Whatever Guy asked for came instantly to hand, and the men whom Vassall had secured were as eager as their employers.

On the fourth day Tyrrell suddenly appeared in the shop. He looked pale and shaky, but vowed he was all right, and insisted on getting to his job again.

The neonite, as soon as produced, was sent in motor trucks, under strong escort, to a Government shell factory about twenty miles away, where the shells were being made.

As for Cratch's gang, if there were any of them left, they made no attempt to interfere. They probably realised how hopeless it would be to do so.

At the end of a fortnight Guy was able to wire to London that his part of the work was finished. Within a few hours came a reply:

CHAPTER XIX
X1 SAILS

'HERE we are again, old son!' said Dick Anson, grinning joyfully, as he met Guy at the head of the gangway.

'Same skipper, same old crew, with a few more chucked in, same blooming lieutenant.'

'But not the same ship, Dick,' replied Guy, as he grasped the other's outstretched hand, and stared past him at the craft which lay in the basin. 'My word, I'd expected something pretty good, but this knocks everything I could have imagined.'

'Oh, she's some ship!' laughed Dick. Then he turned suddenly serious. 'Guy,' he said, 'I don't mind confessing that she almost scares me. She's the most amazing bag of tricks you ever dreamed of, and it puts me in a blue funk to think of the responsibility of having to help to handle her.'

Indeed, she was worth looking at. Up to this time, the largest and most powerful under-water craft constructed were the British V type, of a thousand tons displacement and a surface speed of twenty knots, and the French 'Gustave Zede' vessels, which are 240 feet long, and have a cruising range of 4000 miles.

X1 appeared to Guy to be nearly 300 feet long, and her displacement must have been fully 2000 tons. She had a flat deck, and was apparently well armoured.

'Come aboard,' urged Dick. 'Don't stand there blocking the gangway. You can't tell a thing about her by looking at her from the outside. Come below, and I'll show you a few things which will make you sit up and take notice.'

Guy followed him aboard, and Dick took him below, where they found Commander Mostyn in his cabin, very busy with a stack of charts.

'Come aboard, sir,' said Guy, and there was a twinkle in Mostyn's eyes as he greeted him. He knew, as well as anybody, what Guy's ambition was.

'She is,' said Mostyn emphatically. 'And I am very proud to be in command of her.'

'The old man is as pleased as a peacock with two tails,' Dick told Guy as they started round. 'And so am I, for that matter,' he added, with a grin. 'As a fact, I'd have given a year's pay to get this job. It's going to be the finest show ever, old son.'

There was wonderful machinery for keeping the air sweet, and, by robbing it of all its carbonic acid gas, allowing the ship to stay under water for days on end, if need be. There were new valves and pumps for quick diving and rising. The dynamos themselves contained several improvements quite new to Guy; there were special devices for obtaining the power necessary to fire the electric gun; also the whole ship was divided into several water-tight compartments.

'We have two six-inch guns as well for ordinary use,' explained Dick. 'But the electric gun will be a tremendous pull. You see, since there's no report or flash, there is nothing to give our position away.'

Last of all, they came to the torpedo tubes, of which there were four, two bow and two astern. They were fitted for the largest size Whiteheads. The torpedoes themselves were of a new pattern, which were not only self-steering, but of much greater range than any yet in use.

It was a question which was the keener, Guy or Dick. It was hours before Guy was satisfied, and Dick vowed at last that he was completely exhausted, and would not show Guy another thing until they had both had tea.

That night Guy slept aboard. X1 had real cabins. True, they were very tiny, and Guy shared one with Dick. But the submersible herself seemed marvellously spacious and roomy as compared with Q17, and that in spite of the fact that the Q class were themselves of 800 tons displacement.

Very early next morning Mr Ingram came aboard, and with him no less a personage than Admiral Dayle himself.

He chatted a while, then went into Mostyn's cabin with the Commander, and remained there for about ten minutes.

A brief good-bye, then he went ashore. The engines began to throb, the twin screws revolved, and X1 was off on her adventurous journey.

'Where's Slavinski?' Guy asked of Dick, as they passed out into the main stream. 'Isn't he coming with us?'

'He's here all right. Came aboard late last night. Jolly lucky for us that we've got him. He knows all the tricks of the Baltic, and can put us wise to the mine-fields.'

'Don't know that I ever had any. But I've seen a bit of him lately, and there's nothing of the Hun about him.'

'You bet he does. It takes a Pole to hate like that. 'Pon my Sam, I believe he'd cut every throat in Germany without a qualm.'

X1 was now out in mid-stream. The beat of the engines quickened, the shores began to slide past more rapidly.

'Wait till she's outside. Then you'll see,' replied Dick. 'It 'ud take a destroyer to catch her. Why, she can do twelve submerged.'

Guy looked back at the shore. Early as it was, there were knots of interested people watching the new ship go out.

'About X1? You bet they do. Not her details, of course, but you can be jolly sure they know of her existence. You can't keep that sort of thing secret. For that matter, we have plans of their latest submersibles.'

'I know our Secret Service is jolly good,' said Guy. 'Vassall has put me wise to that. But what I mean is, do you think Fritz knows what we're after on this trip?'

'Can't say as to that,' replied Dick, 'but I hope not. The report has been carefully spread that we are going to have a slam at Bremerhaven.'

'We shall go through at night. There's no moon now, remember. Let's pray for clouds and wind.

'And now,' he added, 'we'll slip down for breakfast. This barky runs to a real cook, and though he's not up to your Hannah, we can do better than sardines and cocoa.'

Dick was right. Grilled kidneys and bacon was the menu, with toast, fresh butter, and marmalade. When Guy came on deck again the land was merely a line on the western horizon, X1 was foaming through a short, gray lop at a really surprising speed.

Nightfall found them in the Skagerakk. So far, there had been no sign of the enemy. They had not even spotted a Zepp, although the weather had turned fine and clear again, with only a very light breeze.

'There's a very good reason for it, old son, and so you'd know if you'd been reading our wireless. At the present moment there is quite a considerable section of the Grand Fleet not fifty miles off Heligoland. I fancy Fritz has quite enough to think of in that direction. He gets nervous as a scorched cat when we start playing games in the Bight.'

Guy opened his eyes. Dick's information helped him to realise the tremendous importance that the High Command set upon this expedition.

On they drove. Mostyn kept on top. There was no saying what would happen when they reached narrower waters, so, in spite of the risk, he preferred to keep his dynamos fully charged against future emergencies.

X1 rounded the Skaw, and turned south into the Kattegat, and still the sea was empty.

'Don't you fret,' grinned Dick. 'We shall have all the trouble we need before we're much older. If I were you, I'd go below and get a calk. You won't get a lot of sleep once we are in the Baltic.'

Guy knew that this was true, and reluctantly went below. But once in his bunk, he was very soon asleep.

He was roused by finding his feet pressed tightly against the partition, and sat up hastily as he realised that X1 was rapidly submerging. He was up in a moment, and beside Dick, who was at the periscope.

'Sighted two destroyers,' said Dick in Guy's ear. 'But they don't seem to have spotted us, so we're just lying low till they've passed.'

'Because we've something better to do, you juggins. Our job is to keep out of trouble until it's forced on us.'

For about twenty minutes X1 sped onwards at a depth of about thirty feet, then she slid cautiously to the surface again. The Huns were gone and the coast clear. Guy, rather disappointed, went to bed again. When he was again awakened by a dive he learned that they were actually in the Sound, and creeping past Copenhagen.

'Nearly dawn, and we've got to be precious careful,' Dick told him. 'Water's none too deep, either, and it might be awkward if a Zepp happened to be overhead. Yes, get up and dress if you like. This is going to be our busy day.'

It was breakfast time before they had passed Falsterke, and were actually in the Baltic. Here it was necessary to be more cautious than ever, for there were mine-fields on either side. Slavinski was at the wheel.

X1, like other large vessels of her class, had two periscopes. Dick and Guy stood by the forward table, waiting eagerly for the picture to appear.

A moment later a circle of blue waves showed on the screen, and Dick gave a growl of disappointment.

'Blazing sunshine! What rotten luck! If there was anything we wanted, it was a dull day.'

'Don't worry,' said Guy. 'The glass is dropping. You often get rain after a bright morning at this time of year.'

'Hallo, what's that?' exclaimed Guy, as a fountain of foam rose suddenly just within range of vision, leaping from the sea like a small waterspout.

Like a flash, X1 dipped her bow and drove downwards. Big as she was, she dived even more rapidly than Q17. Dick and Guy had to cling to the fixed table to save themselves from being pitched forward.

'Perhaps you will, you bloodthirsty beggar, but I'm much more inclined to think that the old man will trust to a mouldy.'

X1 was darting along like a great fish under water. But where she was going, or what was to happen, only Mostyn knew.

'He's keeping her under the mischief of a time,' said Dick, and almost as he spoke up she shot again, and once more the periscope pictured the sea. And there, half a mile away, a destroyer of the very biggest type ploughed past at full speed.

'I see now. It's our speed has puzzled them. Fritz is looking for us in the wrong spot. Wait now, Guy. See him get the jar of his misspent life!'

With a sharp hiss the great steel fish left its tube, and the sea-water gurgled into the compensating tank. Dick and Guy had their eyes glued to the periscope picture, watching the slim white track of the torpedo as it sped onwards.

Busy searching for the submersible, and never imagining that she was where she was, the enemy did not spot the torpedo until it was almost on them. Then the helm was flung hard over.

But it was too late. The torpedo struck her just aft of the first funnel. A vast column of water leaped skywards, mixed with a cloud of smoke and flame, blotting her from sight. When it fell the Hun ship lay over on her side, settling rapidly.

'Going to pick up survivors, Guy. This is all very well; but you mark my words, we'll be sorry.'

Before X1 reached her, the broken destroyer sank beneath the sea, taking most of her crew with her. Not more than a dozen black dots, the heads of swimmers, showed on the surface. Mostyn went slowly ahead and reached the first swimmer. He was grasped by the collar and hauled aboard, and passed unceremoniously below.

Before a second was reached, from somewhere overhead came a thin, faint whistle, which grew in sound and volume like that of an express train approaching at full speed.

Guy looked up quickly, and caught a glimpse of a thin, silvery, cigar-shaped object high among the soft, fleecy clouds.

'A Zepp!' he cried, and as he spoke a great bomb struck the water not a hundred yards away, flinging up a tall spout of foam.

'Rotten luck!' growled Dick. 'That's given the whole show away. Quickly, Guy. Get below. We'll have to dive out of harm's way.'

The wretched swimmers, betrayed by their own airship, screamed for help, but there was no help for them. X1 was in the very act of diving when a second bomb came hurtling out of the blue, striking the water so close to the submersible that the spray was flung all over her.

Like a flash a bag of oil was emptied into the sea, and at the same moment X1 executed a crash dive.

Well under the surface, X1 shot away at a brisk pace, but within a very few minutes came the order to rise again.

Guy, waiting eagerly at the periscope, gave a quick exclamation. 'The Zepp is coming down.'

There was a breathless pause while the great airship dropped rapidly towards the sea. She came straight down towards the oil patch, which was more than a mile from where X1 was now lying.

'But she'll feel us pretty soon,' chuckled Dick. 'Ah, up we go! Now for it, Guy!'

As the whole length of X1 rose above the surface, the Zeppelin of course viewed her, and began to rise again. She went up so swiftly that Guy was in terror they would lose her. He did not need to be told that, if she got away with the news, half the German fleet would at once be on their track.

But fast as she rose, the men of X1 were quicker. In a matter of seconds they were out and had one of the six-inch guns trained on her.

The chief gunner was a tall Cornishman, Penruddocke by name. In a trice he had the muzzle of the long gun trained upon the great airship.

'Fire high,' said Guy. 'Remember, if you burst the shell anywhere within 200 feet above her, she's done.'

The range was about 2500 yards, and for a second Guy believed he could see the shell cleaving the blue.

'Missed her, by thunder!' cried Penruddocke, and then his jaw dropped, and he stared like one who cannot believe his eyes.

For the giant gas-bag had split like a soap bubble. She had not taken fire, but to all appearance every single one of her score or so of balloonets had burst simultaneously. Her framework, gondolas and all, was falling like a stone into the sea.

There were more than a dozen men on X1's deck. For a moment or two they stood staring in utter amazement. Then as, with a mighty splash, the broken fabric crashed into the sea, a roar of cheering burst from every throat.

'So that's neonite!' said the gunner to Guy. 'Well, sir, give me a fast cruiser and enough o' that stuff, and I'd lay out the German Navy, single-handed.'

X1 was now dashing forward at full speed to rescue the survivors. But when she reached the spot, there was no need for her services. There was nothing visible at all except tattered fragments of the fabric of the great airship and splintered pieces of woodwork. Everything else was deep below the sea.

'And a very good job, too,' remarked Dick to Guy. 'If we didn't finish them up like this, X1 would be crowded with prisoners like a penny steamboat before we reached Rosel.'

'I could have told you there wouldn't be any left,' said Guy quietly. 'The explosion killed every soul aboard. They were dead long before they reached the water.'

They went down to lunch feeling that they had done a good morning's work, and Mostyn insisted on opening a bottle of champagne to drink Mr Ingram's health.

'I feel,' he said,' like Penruddocke—capable of tackling the whole German navy. I drink to your invention, Mr Ingram—the most terrible thing ever evolved by man's brain, and at the same time the most valuable, in that it is going to end this war and, I think, all wars.'

'I trust you are right, Commander Mostyn,' he said. 'And I thank you for what you have said.'

Then he relapsed into silence, and Guy, watching him, knew that he was thinking of his boy, and wondering what his fate would be in the bombarded city.

X1 was now proceeding at full speed on the surface, and after lunch Guy and Dick went up again.

The sun was gone, gray clouds covered the sky, the temperature had fallen several degrees.

CHAPTER XX
THE STRICKEN CRUISER

'WELL on our way now,' said Guy, as he and Dick stood gazing at a low-lying island to the south. It was Bornholm, Denmark's most easterly possession. They were well outside Swedish territorial waters, but a long way north of the German coast.

Dick nodded. 'All right, so long as that Zepp didn't wireless before we sent her to glory.'

'Phew! I hadn't thought of that. But in any case it's getting so thick they'd have a job to spot us.'

'Oh, we're not likely to have any trouble at present,' rejoined Dick. 'What I'm worried about is that they may have got the news at Rosel. Nice job for us if they've thickened that ice-sheet of theirs.'

'We can't afford to waste neonite on ice,' replied Dick, rather shortly. 'Our stock won't be too much to tackle the town and fight our way back with. Kindly remember that we shan't get back as easily as we've come.'

'There's plenty of time to think of that,' replied Guy easily. Hour after hour they drove steadily onwards, and before nightfall had passed the great Swedish island of Gothland, and were nearing their destination. The weather remained dull and cloudy, with a chill wind. Visibility was bad, which was just what they wanted. As for shipping, there was none in. They might have been in the Antarctic for all they saw of steam or sail. All merchant traffic seemed to have cleared.

About ten o'clock the atmosphere became distinctly colder, and there was an air of repressed excitement aboard X1. Every one knew that they were at last nearing their destination.

Mr Ingram became more and more restless. Guy, knowing what he was suffering, was desperately sorry for him. He himself was feeling badly enough. If they did bombard the Secret City, he could not for the life of him imagine how Wallace was to escape. Neonite spared nothing, and unless Wallace was in some place very deep underground and well cut off from the outer air, he would certainly share the fate of his jailers.

A pencil of light came swinging through the smother. It had a curious golden glow, which penetrated the fog in a startling fashion.

'Another new trick of theirs,' said Dick. 'That searchlight must have a patent lens. It beats anything of the sort I've over seen.'

Mostyn brought his ship down to a crawl that gave her barely steerage way. But the searchlight swung past and well overhead and failed to illuminate the long dark form of the avenger.

By this time it was bitterly cold, and those on deck were wearing winter lammies.

'It is as I expected,' said the Pole, fixing his bright, eager eyes on Guy. 'They have widened the ice-sheet. It now stretches for more than a mile around the island.'

'It is the better,' declared Slavinski, with conviction. 'They will think themselves perfectly safe behind such a protection.'

Slavinski nodded. 'But the wind strengthens,' he said. 'Before morning it may be enough to blow it away.'

'Wonder what Mostyn means to do,' he said to Guy, in a low voice. 'He hasn't told me a word yet.'

'You, too, Hallam, and Slavinski. Barton will take the wheel. We shall be lying to for a bit.'

Below Mr Ingram was waiting for them, and all five went into the Commander's cabin.

'It's too thick to start shooting to-night,' began Mostyn. 'I propose to go round to the windward side and lie on the bottom until conditions improve. But what I want to tell you all is this. Slavinski has volunteered to go ashore and endeavour to rescue Mr Ingram's son, or else to get him into a position of safety during the bombardment.'

Complete silence followed this announcement. All eyes were fixed on Slavinski. A slight flush rose to the sallow cheeks of the slim little man.

'It is a terrible risk,' said Mr Ingram gravely. 'Much as I value my boy's life, I do not wish to allow Slavinski to go to almost certain death on his account.'

'The risk, it is not so great as Mr Ingram thinks,' he said, speaking in his usual very good English, and with only a slight foreign accent. 'Remember, if you please, that I am well acquainted with the place, and that I shall be wearing their own accursed uniform. I think I shall be able to help Mr Ingram's son, and I very much wish to. You have all'—his voice was a little husky—'you have all been so kind to me, a stranger.'

'It seems to me that Mr Slavinski ought not to go alone,' he said. 'Even if he does manage to find Wallace Ingram, Wallace won't trust him. You see, the last time they met, Slavinski was one of the crew of the U-boat. Why shouldn't I go with him?'

'That is out of the question, Mr Hallam,' he answered decidedly. 'I can disguise myself, but not you. Besides, if I may say so, your German is not good enough. I am grateful, very grateful, to you, but I assure you it is impossible.'

'That will be the best plan,' agreed Slavinski. 'And now, gentlemen, if the Commander will agree, I will at once change my clothes and be landed on the edge of the ice-belt.'

'If you really mean it, I won't say no. You must be quick though. If the fog should lift suddenly, it will be awkward.'

'I should rather think it would,' said Dick to Guy, as Slavinski hurried away. 'They've got some thundering big guns on the island, I hear, and our only chance will be to keep moving pretty quickly if they once start shelling us. The fog is our best friend.'

'I'm jolly glad you're not going to do anything of the sort, you old idiot,' replied Dick. 'It's bad enough to let Slavinski go. But he, at any rate, can pass as a Hun.'

'Don't worry. You'll have all you want before you're twenty-four hours older,' replied Dick, with a grin.

Meantime the big submersible was slowly feeling her way forward. The cold was intense, and soon through the thick waves of fog came the white blink of ice.

There was a slight crunch, and X1's steel bow actually touched the thin edge of the ice-field.

Slavinski came up on deck. He was wearing the same uniform in which he had first come aboard Q17, and looked rather ashamed of it. He also had on a life-belt.

'It will not be cold in the Secret City,' replied the little man, smiling. 'It will be what you call, in English, a hot shop.'

'I shouldn't wonder,' said Mostyn. 'Take care of yourself, Slavinski. You have your story all ready, in case awkward questions are asked?'

'I have it quite ready,' replied Slavinski. 'I have also something else ready.' He touched his pocket, in which was stowed a small but powerful automatic.

'That is for Steubel,' he added. 'If I should have the good fortune to meet him.'

As X1 crushed her way forward into the splintering ice, Mr Ingram took Slavinski's hand.

'Good-bye,' he said. 'Good-bye, and good luck to you. You are a brave man, and I believe that you will succeed in your mission. If you can save my boy, you will have done as much as one man can do for another.'

'Never fear, sir,' said Slavinski. 'I will save him for you.' Then, without another word, he stepped out on to the ice and, with one wave of his hand, turned and made straight away for the hidden shore.

For a moment or two the rest watched him in silence. Dick was the first to speak.

'He's got cast-steel pluck,' he said. 'I say, Guy, why does he hate Steubel like that?'

'Steubel was in the U-boat with him, and treated him like a dog. The Prussian crowd loathe the Poles, and the Poles hate them. Slavinski has a special down on both Steubel and von Fromach, and, as he doesn't care two pins for his own life, I'd hate to be in the shoes of either of them.'

While he was speaking the submersible backed out of the ice and proceeded slowly around the western edge of the ice-sheet.

All the crew were enormously interested in the Cold Ray and its effects. Guy overheard one man say to another: 'The loo'tenant were right, James. Them chaps at the Admiralty thought he were loony, but he were right as right could be.'

'He were,' answered the other. 'Lumme, George, it's just as well as we're here to bust this thing up. Think if Fritz started to freeze up old England! Wonder what my old woman would say?'

The fog was not so thick on the windward side of the island, but still far too thick to get any view of the land itself. And as the weather showed no signs of improvement, Mostyn wisely decided to submerge and wait.

The tanks were filled, and presently X1 was resting quietly on the bottom in some sixty feet of water.

Guy turned in, but was too excited to sleep. He was thinking of Slavinski, mentally following him across the ice, and up the low cliffs. He wondered how he would pass the sentries, and whether the people in command would believe his story.

Slavinski, if questioned, was to say that Q17 had come back again, with a view to getting hold of Wallace Ingram. He was to tell them that Mr Ingram had refused to manufacture neonite for the British Government unless his son was restored to him. To explain his own presence on the island, he was to say that he had been taken prisoner when U299 had been sunk, and that he had volunteered for the job, hoping to get the chance of warning his own people.

'A precious pack of lies,' said Guy to himself, 'but what can you do when you have to deal with carrion of this kind. Besides, Slavinski is so smart, he'll very likely get in without any one spotting him at all.'

It was strangely quiet down there at the bottom of the sea. Since there was no need for a watch, practically every one was asleep. At last Guy himself dropped off.

It seemed to him that he had hardly closed his eyes before Dick Anson was shaking him by the arm.

'That depends,' replied Dick. 'The fog may be as thick as ever, or the German navy may have arrived. You never can tell.

'Take it easy,' he went on, with his cheery grin. 'There's no great rush. Anyhow, we're going to breakfast before we put our noses out into the cold.'

Coffee was ready as soon as Guy was. Coffee, with fried ham, toast, and marmalade. In spite of his excitement, Guy stowed away a good meal. As Dick cynically observed, 'You don't know when you'll get another.'

Mostyn got up from the table, brushed a few crumbs from his uniform, and gave an order. The dynamos began to throb, the pumps to work, and lifting off the bed of soft sand where she had spent the night, X1 rose gently to the surface.

'Thick as ever!' was Dick's disappointed exclamation, as light fell on the screen of the periscope.

'Not quite, Anson,' replied Mostyn quietly. 'No, it's by no means as bad as it was last night. There's a fair amount of wind, too. I think that, in an hour or so, we ought to be able to make a start. Meantime—'

'The German navy, or a section of it,' said Dick dryly. 'A whacking great cruiser came into the edge of the picture.'

'Jove, she's seen us, too!' he added, as a dull concussion sounded overhead. 'That's a shell, Guy. Big stuff, too. We shall have to silence her, or there'll be all kinds of trouble brewing.'

While he spoke X1 was darting seawards under the full power of her electric engines. Presently came the heavy shock of a depth charge, sending a quiver all through the great steel frame.

'Nearly a mile away,' remarked Mostyn. 'Fritz is clean off the track. I think we can safely go up and have a squint at him.'

Marvellously handy in spite of her size, the submersible slid again to the surface. Already the fog was thinning, and they were just able to see the big bulk of the cruiser racing for all she was worth along the edge of the ice-sheet.

With startling speed, the long thin tube of the electric gun had been raised from its bed, and half a dozen narrow, winged neonite shells were ready beside her.

Penruddocke was there as soon as Guy. Guy's job was merely to see that the loading and adjustment were correct. He had nothing to do with the firing. Now that he was really in action, he no longer felt any nervousness, and his hands, as he lifted the shell, were as steady as if he were simply playing a game of billiards.

By this time Fritz had sighted them. The big cruiser was in the act of coming round as Penruddocke put his eye to the telescopic sights.

A dull roar broke through the fog, and a big shell came rushing across the sea with the sound of an express train. It passed so close overhead that Guy actually felt the wind of it, and, plunging into the sea fifty yards beyond, went ricochetting away across the gray waves.

'Direction good, elevation bad,' remarked Dick Anson, and as he spoke Penruddocke pressed the button making the electric contact.

Almost before the words were out of his mouth there was the thud of an explosion in the direction of the cruiser.

The cruiser—she was a ship of six or seven thousand tons—had stopped as dead as though she had hit a cliff. Her decks lifted just as if her magazine had exploded, and with one accord all her three funnels went over the side.

A great cloud of smoke and dust arose from her, and she lay wallowing drunkenly on the short, gray seas.

'She's finished already,' remarked Guy quietly. 'Barring her stokers, there isn't a soul alive aboard her.'

An amazed silence followed the words. Every one on the deck of the submersible was staring at the strangest transformation scene.

Over a wide circle all around the stricken cruiser the fog had absolutely vanished, and the clear circle was increasing with startling speed. The sun was breaking through into the gap, turning the tossing seas to pale gold.

'It's the neonite,' explained Mr Ingram, who, in spite of Mostyn's protests, had insisted on coming on deck. 'It is the result of the vacuum. The clear space will spread still further.'

'It's spreading a deal too quickly for us,' said Mostyn grimly. 'Ah, I thought as much. There is the island itself in sight.'

CHAPTER XXI
GUY GOES OVERBOARD

LIKE magic, the northern edge of the hidden island sprang into view. Solid-looking buildings became visible, a tall chimney smoking heavily, and the lofty iron-work tower of which Dick had spoken. The wide ice-belt glittered in the sunlight.

'All guns. Neonite shells,' snapped out Mostyn. 'Quickly, men! If we can see them, they can see us.'

The speed with which the men obeyed proved that they realised the danger as well as did their commander. But quick as they were, they were no quicker than the enemy. From one of the hidden forts ashore a great gun roared, and a huge shell came tearing towards the submersible at almost point-blank range.

Lucky for her that she was travelling at the top of her speed. The monstrous missile struck the water barely her own length astern, flinging up a fountain of spray many feet into the air.

Next instant Penruddocke and Guy, between them, had fired the electric gun. For want of any more definite mark, Penruddocke had aimed at the factory chimney.

The shell seemed to burst right against it, and instantly the tall column of brickwork splayed out and fell in fragments. It was exactly as though a heavy charge of dynamite had been exploded in the shaft itself.

Then with a double crash the two six-inch guns flung their hundred pound shells, pitching them clean into the centre of the Secret City.

What they hit could not be seen from the deck of X1, but enormous clouds of dust were flung up, while the air disturbance created by the double explosion seemed to cause something like a whirlwind over the island.

'Get to it!' cried Dick. 'That's shaken them up, I'll warrant. Quick as you can fire, lads.'

Three more shells in rapid succession went flying on their deadly errand. Guy was lifting another when he heard Dick's voice at his elbow.

Dick was right. The cold was simply frightful. The spray flung up by X1's rapid rush through the water froze as it fell. Hard as the gunners were working, their fingers were blue with the bitter frost.

'They've turned the Ray full on us,' replied Guy, between chattering teeth. 'We've got to knock it out or they'll do for us yet.

It was a twelve-inch, and closer than the first. Having got over their first surprise, the Germans were retaliating with all their might. The din was simply appalling, shells big and little came roaring, screaming, and whining across the ice and sea.

It seemed a miracle that X1 was not hit, but Mostyn kept her twisting and turning like a hunted hare, and somehow she escaped.

Meantime her gun crews worked with savage energy, loading and firing with amazing speed. And with every shell they fired the reply from the shore batteries became more and more feeble.

'We're doing 'em in, Guy,' cried Dick, his eyes alight with excitement. 'Spray your shells wider, men. We must smash up that Cold Ray outfit, or we shall all freeze stiff. Gosh, I only wish I knew where the plant is!'

'Try that steel tower to the right,' ordered Mostyn, who himself was at the wheel.

As he spoke there was a sound like a clap of thunder. X1 reeled, and for a moment seemed to stop dead. Then a great wave washed right over her, and Guy, swept from his feet, found himself clinging to a stanchion, gasping in the icy flood.

Whether the submersible had actually been hit or not he could not tell, but one thing reassured him—the engines were still running.

That was the next thing he heard, and looking out he saw a head bobbing in a welter of spray almost within arm's length.

Almost, but not quite. Clinging to the rail, he made a grab, but just failed to reach the drowning man. In the same instant he recognised him as Mr Ingram.

Quick as he was, the inventor's head was vanishing beneath the sea as Guy reached him. Guy grasped him by the collar dragged him up, and turned to strike out again for the ship.

He had forgotten her speed. To his horror, she was already out of reach, and shooting away with what seemed the pace of a train. Shells were still falling all about her, and he realised that, much as he might wish to do so, Mostyn dared not stop to pick him up.

So here he was, cumbered with a man who seemed insensible, and at any rate could not help himself, and both left to their fate in water so bitter cold that they could not hope to live in it for more than a few minutes.

As X1 swirled away, he caught a glimpse of Dick Anson waving and pointing frantically. He looked and saw a life-belt bobbing on a wave top, quite close by.

He grasped it and, though rapidly growing numb with cold, managed to clasp it around Mr Ingram. Then, as there was no choice, he set himself to swim to the ice edge, dragging Mr Ingram behind him.

Guy was a fine swimmer. He had showed his powers in that direction when he got Dick Anson out of the tide up in Galleon Gap. Here there was no current, and the task would have been an easy one but for the cold. But the cold was frightful. It crept into his very bones, stupefying him and paralysing all his efforts. His heavy clothes, too, dragged him down.

He sank lower and lower in the water until the icy little waves broke over his head. It was sheer will-power that kept him going. His straining eyes were fixed on the white edge of the floe, and everything else was forgotten in a savage resolve to reach it.

At last he was against it, and stretching out his right arm, flung it across the white surface.

The stuff was mere slush and broke away. Guy gave a groan of despair, yet even now he would not give up. Dragging Mr Ingram behind him, he forced his way forward, breaking the ice as he went, and trying to find a part thick enough to bear his weight.

But it was salt-water ice, rotten and more like melting snow than anything else. He felt it was useless. His strength was failing under the effects of the intense cold. He was almost at his last gasp when a dark object embedded in the ice just ahead caught his eye.

With a last struggle he reached it, to find that it was the end of a great balk of yellow pine, flotsam, no doubt, from some torpedoed Russian vessel.

It was forty or fifty feet long, and its inner end firmly fixed in thicker ice. He climbed astride it, and, waiting a moment to get his breath, pulled Mr Ingram up after him. Then, creeping along the balk, he reached ice thick enough to bear their double weight, and struggled stiffly to his feet.

He looked down at the inventor. The latter was quite insensible. Guy felt his heart, and found it still beating. But in this temperature he knew that exposure must mean death. There was only one thing to do. Whatever the risk, he must get Mr Ingram into shelter. Hoisting him on his back, he started across the ice towards the island.

It was madness. The Huns, savage at the attack, would probably turn a machine gun on him. But there was no choice. With his feet sinking at every step in the slushy surface of the ice, Guy staggered on.

Ever since he went overboard, he had been so desperately set upon saving Mr Ingram that he had not had a thought for anything else. Now it suddenly struck him that the firing was dying away.

He looked towards the island. The sky was so clear that he could plainly see the circle of the tiny barrage balloons set high in the sky, held in place by their invisible wires. Down below was a turmoil of dust and smoke, but not a single gun seemed to be firing from anywhere on the island. He realised that what firing he still heard came from X1, and, looking back glimpsed her some three miles away to the south west.

Then something else occurred to him. The air was decidedly warmer. He was no longer shivering under the influence of the Ray. And the ice was beginning to steam as a meadow does when hot sun follows on a cold shower.

He could have shouted with delight, but the thought of Wallace rose to his mind and checked his joy. Slavinski, too. He wondered what had become of him. He had come to like the plucky little Pole.

He looked back again. X1 had turned and was coming in fast towards the ice. Within a very few moments she had reached the edge of the sheet.

A gun was fired. By the sound, the charge was a very small one. The shell exploded over the ice only a few hundred yards from X1.

If Guy had not been well acquainted with the power of neonite the result would have amazed him. Acres of ice broke up, the fragments tossing in the bubbling water. He felt the shock under his own feet. The whole ice-sheet cracked and quivered.

Two more shells and X1 had an open passage clear into the little harbour of the island. Although Guy hurried as fast as his heavy load allowed, the submersible reached the shore before he did.

Almost dead beat, he struggled off the fast melting ice on to the sandy beach, and found shelter from the wind under the low cliff. Here he laid Mr Ingram down, and without a moment's delay set to stripping and rubbing him.

Not a soul came near him. There was not a sign of life on the island—not so much as a sea bird.

Under Guy's vigorous hands, the old man stirred and opened his eyes. He shivered.

Guy was desperate. The inventor was in a bad way. And he himself had not even a flask of spirit, let alone a blanket.

Steps came crunching across the shingle. He looked up and saw two of the men from X1 doubling towards him with a stretcher.

'Ay, ay, sir. Brandy and a couple o' blankets and a hot brick. Here's the flask, sir.'

Guy poured a couple of spoonfuls down Mr Ingram's throat, and quickly wrapped him in the blankets.

'I will that,' Guy promised. 'You two take him quietly back to the ship,' he said to Cray and the other. 'I must get along.'

'Begging your pardon, sir, you'll take a sup o' this first,' said Cray, who was regarding Guy with open admiration. 'You'll be needing it after that there swim. Lord, sir, I wonder you wasn't froze to death!'

'I was nearly,' confessed Guy, with a laugh. 'But I'm all right now. Still, I will take a little brandy.'

'No harm done to speak of, sir. We did get hit once, but as luck had it, the shell was a small one. Killed poor Bill Hassocks, but that's the only casualty so far.'

'Not a lot, sir,' replied Cray, with a grin. 'Them there neonite shells—lumme!' Cray had no words to express what he really thought of them, but his tone was enough.

'Then I'll be going,' said Guy, and was off down the beach as fast as his slight limp allowed.

The going was good, and it did not take him long to reach the little bay in which X1 lay. She was up against a slip which, however, was in ruins, as were the buildings immediately behind. Two large cargo steamers lay sunk at their moorings close by.

Picking his way through the ruins, Guy saw Dick Anson in charge of a landing party of a dozen picked men. He gave him a shout, and Dick turned and waved his hand.

Guy found himself stumbling through the most amazing mass of rubble and broken masonry. Nowhere was there left a door, a window, or a roof. The place looked like one of those ruined villages in France, and well as Guy knew what neonite could do, he was struck with a sense of complete bewilderment to think that a few score comparatively small shells could produce such an amazing effect.

Dick and his men had stopped, and were waiting for him. They gave him a cheer as he came limping up, and Guy flushed with sheer pleasure.

'I wouldn't have given twopence for his life when I saw him there in the sea,' said Dick. 'Nor for yours either, old son, when you went after him. Great ghost, you must be frozen! Hadn't you better get back to the ship?'

'Not I!' returned Guy emphatically. 'I've promised Mr Ingram to help find Wallace, and I'm not going back till we do.'

'Then come on,' said Dick. 'By the look of things, we shan't find any one to stop us.'

Guy fell into step alongside Dick, and the party marched forward through the ruins.

There were six or seven of them lying together out in the open. A shell must have burst near them, and they were not a pretty sight. Guy felt rather sick.

There were more farther on, and here, where one of the larger shells from the electric gun had done its work, the ruin was indescribable.

'There are underground shelters somewhere,' Guy replied. 'You may be quite sure of that. If nothing else, they would have some place to keep their stores. This seems to be the main square of the town. Let's work round it.'

'What about that there place on the little hill?' suggested Poulton, the torpedo man. 'The one as was under the big steel tower.'

Dick looked. 'I shouldn't wonder if you are right, Poulton.' he answered. 'We'll try it, anyhow.'

The building had no roof, windows, or doors left, but the thick walls still stood square and solid. They reached the entrance and looked in.

The place was a tangle of broken machinery. Great metal tanks, all burst outwards, were mixed with twisted steel rods and leather belting. A strong reek of chemicals hung about the ruins.

'Not much doubt about it,' said Guy. 'Now I wonder if there's a cellar beneath.'

'We'll have a look,' said Dick. 'Scatter, men, and see if you can find any opening. But don't go down. Let us know at once.'

With a rush the men were all over the place, scrambling among the broken stuff, and nearly choking with the rank fumes.

Guy and Dick hurried forward, and found several men grouped around a heavy steel flap-door set in cement.

Two got hold of a ring bolt, and up came the trap. Below, a flight of stone steps led down into darkness.

Dick snapped on an electric torch, and with that in one hand and a pistol in the other, led the way. He ordered Poulton and another man to accompany him and Guy.

There were fourteen steps. Then they arrived in a large underground chamber. Cases and carboys were stacked around the walls. Compared with the ruin up above, the place struck Guy with a pleasant sense of order and neatness.

'If young Ingram's down here, he ought to be all right,' said Dick. Guy nodded. All the same, he did not feel very hopeful.

'Can't see or hear any one,' he answered. 'There doesn't seem to be anything here except stores.'

Dick flashed his light all around. 'There's an opening beyond,' he said swiftly. 'And, by Jove, I believe I heard a movement!'

CHAPTER XXII
FACE TO FACE

A SOLID-LOOKING arch of masonry was what Dick's light showed. Beyond was another cellar. The little party stood absolutely still and quiet, straining their ears for any sound.

'No more can I now,' Dick answered, 'but I vow I did hear something move in the dark there. Wait now. Let me go first.'

He advanced cautiously, and flung his light through the opening. Here again were masses of stores of every description. There were two tiers of boxes and barrels down the centre of the place, piled so high that they really reached nearly to the roof.

Dick stepped inside, stopped, and again held up his hand for silence. Then he made a quick step forward.

There was a breathless pause. Then a step was heard, and from behind the far end of the central pile of cases a man stepped out into the white ray of Dick's electric.

Cratch it was, or Stebbins, or Steubel. The arch-spy was at last in their power. Yet the man looked as cool and unconcerned as on that day when he had visited Claston with his treacherous message. He was dressed in German naval uniform, and stared straight at the Englishmen with an odd light in his curious eyes.

'Wait a moment, Lieutenant Anson,' replied the other in his excellent English. 'Before I do as you request, I desire to know what terms you are disposed to grant.'

'Terms!' repeated Dick scornfully. 'You had better ask the court martial who will deal with you.'

'Ah, but I do not propose to be dealt with by any of your British Courts—martial or otherwise,' replied Steubel softly.

'Wait!' as Dick made an impatient step forward. 'Any violence on your part and you sign the death warrant of a person whose life means, I believe, a good deal to you.'

'You are right, Mr Hallam,' he said. 'Wallace Ingram is in our power. I have only to give a signal and he dies.'

'I think you will hardly be fool enough to do that,' returned Dick Anson dryly. 'You would not survive him for any appreciable length of time.'

'Perhaps so,' he answered. 'At the same time that would not restore young Ingram to his father. To put it plainly, we have a pawn and we mean to use it. Our terms are the lives and liberty of Captain von Fromach and myself in return for the safety of your young friend.'

'You must be perfectly well aware that I can make no such terms,' replied Dick curtly. 'If you have any sense at all, you will surrender at once. Of course, you are a known spy, but since you are taken on your own territory and not ours, that may count in your favour.'

'Switch off your light for a moment,' came Guy's soft whisper in Dick's ear. 'By accident.'

Dick never gave the slightest sign of having heard, yet next moment his finger seemed to slip from the trigger of the torch, and for an instant all was darkness. The light was on again in a couple of seconds, but in that brief space of time Guy had soundlessly vanished behind the piled up cases.

'Confound the thing!' said Dick angrily, as the catch clicked and the light once more blazed out.

'I know no more than you,' retorted Dick. 'No, don't move,' he went on, with sudden fierceness. 'If you do, I'll shoot you in the leg first and then hand you over to be hung.'

Guy, gliding on tip-toe up the far side of the tier of cases, heard Dick's words, and gathered that Steubel was hesitating whether or not to give the signal. He himself was in a state of the most desperate anxiety. Although he was not quite in darkness, yet he could not see von Fromach or Wallace, nor could he tell exactly where they were. All he knew was that, from what Steubel had said, they must be somewhere close at hand. The spy had said that he had only to give a signal and Wallace would die. So it was certain that he was within sight of them.

He saw that the two tiers of cases between which he was moving ended before they reached the wall, leaving a gangway running at right angles to the passage he was travelling down. Almost certainly the two were at one end or the other of this gangway. The question was which. If on the left, he might hope to be in time, if not—in that case there was hardly a chance. He did not believe that Steubel would hesitate to give the signal, and he knew that von Fromach was a Prussian of the worst and most brutal type, who would undoubtedly carry out the sentence.

The strain on his nerves was frightful. Wallace's life depended entirely upon him.

Dick had only just stopped speaking. Steubel apparently was still hesitating. And in that momentary pause Guy heard a rustle to his left.

His heart leaped. Now he was certain. The only question was how to get at von Fromach. Everything depended on speed.

Dick's torch shone strongly into the end gangway in which Steubel was standing. Guy could not see Steubel, nor Steubel Guy, because of the piled-up cases to Guy's right.

Half a dozen swift, silent steps brought Guy to the end of the pile. Peeping round the angle to the right, Guy saw Steubel not ten feet away. His hands were still above his head, and he was staring straight in front of him. But his lips were tight, and his eyes were open. He showed no outward signs of fear, and much as Guy loathed him, he could not but admire his pluck.

Then Guy looked to the left. Again his heart throbbed. There was Wallace tied like a mummy and gagged. He was seated on the floor, his legs straight out, his back against the wall, and over him stood the brute von Fromach, glowering down upon his prisoner and holding a heavy revolver in his right hand.

In the dim light the man's evil face was savage with hatred, but there was also fear in it. He had bitten his lower lip until it bled.

Guy realised instantly that it was useless to make a rush. The distance was at least twenty feet. Von Fromach must see or hear him, and would have plenty of time to kill Wallace, and probably to shoot Guy himself as well.

'Shoot or not as you like, Lieutenant Anson. I have stated my terms. I shall not alter them in any way. I give you while I count five for you to accept or to refuse them. But be quite sure of this, that, if you do refuse them, Wallace Ingram dies.

Guy raised his pistol and took careful aim at von Fromach. It was a hateful thing to shoot a man who could not even see him.

Von Fromach's face looked ghastly, but Guy could see his finger tightening on the trigger of his revolver.

The Prussian gave a convulsive jerk, but the crash of his revolver followed instantly on Guy's shot.

'Wallace!' cried Guy, in horror, for Wallace had rolled over sideways, and was flat on the floor. 'Wallace!'

With a violent effort von Fromach recovered himself and blazed straight in Guy's face.

He dropped to his knees. Half dazed, he saw von Fromach's revolver raised again, and flung himself flat on the concrete floor.

The Prussian fired again but missed, the bullet passing just over Guy's prostrate body. Once more he pulled the trigger, but there was only a snap. He had used his last cartridge.

Guy's head was ringing. He could hardly see. But his full belief that this brute had deliberately murdered Wallace filled him with a fury that gave him the strength of two men.

Entirely forgetting his pistol, he flung himself on the fellow, and, catching him by the throat, with both hands drove him back against the wall.

Von Fromach fought like a cornered wolf. He kicked and even bit at Guy's bare hands. His strength, too, was great, with that deep chest of his and his thick neck, and monstrously long arms.

Guy clung to him like a bull dog, squeezing the breath out of him, and presently down he went, with Guy on top.

Even then he was groping for his pistol, which lay on the floor close by. Guy did not give him a chance, but went on choking him until his face turned blue, and with a horrid gurgle he fell back, limp and insensible.

Guy lifted one hand vaguely to his head, and brought it back, covered with blood. Then everything began to spin around him. He tried to rise again, but could not. Twice he attempted it, but each time only to fall back. All went black, and he collapsed in a heap on top of his insensible enemy.

* * * * * *

'I never thought he had it in him. He went for that Hun like a destroying angel.'

'The funny thing was,' the voice went on,' that he must have forgotten all about his pistol. He had only fired one cartridge, and that bullet didn't do much damage. It only bored a hole between two of von Fromach's ribs, while the Hun got Guy right across the scalp with his great heavy .38 calibre bullet.'

'It was fortunate for him that it was not lower. A quarter of an inch would have made all the difference,' answered another voice gravely, and Guy, who was slowly rousing out of his state of coma, knew it for that of Mr Ingram. 'But why,' went on Mr Ingram, 'why do you say, Anson, that you did not think he had it in him. Surely the way in which he went into that freezing sea after me is proof enough of his pluck.'

'Bless you, I never doubted old Guy's pluck!' returned Dick quickly. 'Heavens alive, I shan't easily forget how he lugged me out of Galleon Gap that day I dropped out of the Hun balloon. All I mean is that I didn't quite credit him with that sort of Berserk business. I never thought he was so strong either. I only wish you had seen it, Mr Ingram. There he was, with the blood streaming down his forehead, and scragging that bull-necked brute as a terrier throttles a rat. It was all because he thought the swine had finished poor old Wallace.'

'Wallace!' he said, in a voice which was very weak and hoarse. 'Isn't he—didn't von Fromach kill him?'

'You blighted old eavesdropper!' he exclaimed. Then, seeing Guy's pale strained face and anxious eyes, he changed his tone at once.

'No, Guy,' he said quickly. 'Wallace is right as rain. Von Fromach meant to kill him, but the lead pill you gave him spoilt his aim, and Wallace had sense enough to roll over and play 'possum.'

Guy gave a gasp of relief, but he still looked as if he could hardly believe what Dick said.

Mr Ingram, who, still rather pale and weak, was sitting in a chair beside Guy's bunk, stretched out his hand and took Guy's.

'Anson is right, Guy,' he said. 'Wallace is quite unhurt. And it is you—you whom I have to thank for saving him for me.'

There was a moment's silence, broken only by the steady roar of the engines. Dick, for some reason, had a lump in his throat. He was thinking how very near he had been to losing Guy altogether. And although the two had not known one another for any very long period as time went, yet there was a very deep and real friendship between them.

'Nothing special, old man. We made those two beggars fast and set a light to the stores. Then we cleared out, and now we're plugging home as fast as our engine will carry us.'

'Von Fromach. From what Wallace says, Slavinski managed to slip into the Secret City unseen. He bluffed the sentries. Then he must have tried to find Wallace, but failed. No wonder, for Wallace was down there all the time in that underground place. Slavinski went straight to the Governor Baron von Schlesinger, pitched him his yarn about having escaped from a British submarine, and the Governor seems to have swallowed it. At any rate, he told Slavinski that Wallace was safe enough under the Power House.

Just then, it seems, von Fromach came in, spotted Slavinski, and accused him of having jumped overboard from the U-boat and deserted. What happened next I don't know, but Slavinski was arrested and court-martialled, and sentenced to be shot this morning. They put him down next to Wallace last night, and I am telling you what he told Wallace.'

'Not in time to stop von Fromach from acting as his executioner. He went down there just after the first of our shells burst up that tower. He must have known it was neonite, and that the whole place was doomed. Wallace says Slavinski simply laughed at him, so the brute shot him dead on the spot.'

'He'll pay right enough,' Dick answered grimly. 'Mostyn vows that if anything happens to us he'll finish the fellow with his own hands rather than let him get loose again.'

'Couldn't be better. Glass tumbling again, and as dirty a day as any one could wish for. The clouds are down on our heads. You can't see a mile.'

'They'll be waiting for us in the narrow waters,' said Guy. 'Time enough to think of that when we get there,' replied Dick. 'Meantime I'm going to tell the cook to bring you a bowl of that tinned oxtail soup, and after that you can curl up and snooze. You'll have to go easy for a bit, Guy. You have a nasty dint in your head.'

Guy had to confess that he still felt pretty muzzy. He had his soup and was soon asleep.

When he woke again, X1 seemed to be nearly standing on her head. Guy had to hang on to save being flung out of his bunk. Then she pitched the other way. Guy realised that the weather must have grown much worse.

After a while Dick came along, and stood clinging to the side of the doorway of the tiny cabin.

'Blowing like blazes, Guy,' he said. 'To tell truth, I never saw it much worse. It's a real snorter.'

'He means to—till the last minute. We've got to save all our power for the run through the Straits. With a full charge we ought to be able to go the whole way submerged.'

'You bet! Even a destroyer could hardly live in this. We've just seen a Zepp out of control; she was being buzzed away like a dead leaf.'

'Not if this lasts. It's just about the best thing that could have happened, old son.'

Dick was no doubt right, yet for all that the next few hours were purgatory for Guy, and indeed for every soul aboard X1. But Mostyn hung on grimly, and when they got under the lee of the Swedish coast it was not quite so bad.

But if the bodies of X1's crew were sore, their spirits were high. They had not seen a sign of a Hun ship since leaving the smoking ruins on Rosel. Above all, if the gale lasted, they were safe from planes. And planes, they had all known in their hearts, would have been a most deadly danger if the weather had been fine and bright. Much of the Straits were shallow, and a ship the size of theirs is hard to hide unless she can get fifty or sixty feet below the surface.

It was not until long after nightfall that Mostyn at last gave the order to submerge.

The relief was enormous. It was like running into a sheltered harbour out of a heavy gale. Guy, worn out with many hours of desperate tossing, went sound asleep again, and left to others the task of navigating through the tangle of mine fields.

Having carefully charted their way in, they were able to keep the same course on the return journey, and as the night was black as pitch and the nor'wester still howled savagely over the tossing sea, they were not molested in any way. By noon next day they had safely rounded the Skaw, and were able to come up to the surface for a breathing space.

The gale had blown itself out, but clouds still covered the sky. Far to the south they saw smoke, but there was nothing in sight near at hand.

Guy, much the better for his long sleep, clambered up on deck, and filled his lungs with the keen salt air. Dick pointed out the smoke.

'Ours, by Jove! There's a scrap on!' exclaimed Dick. 'I'd give something to know what's up. Hallo, Mostyn means to find out. Get below, Guy. We're going to submerge.'

Well beneath the gray surface, X1 turned her slim shape in the direction of the firing. The excitement was great. Every one was mad keen for another trial of neonite.

A quarter of an hour's quick run, then up went her periscope again. Their eyes were hardly on the picture before a spout of water rose from the sea only a few hundred yards away.

'Bang in the middle of it,' cried Dick. 'Look at it! Four—no, five Huns and only two of ours. And one of ours in a bad way by the look of her.'

Mostyn had seen enough. He was snapping out orders. In record time X1 was on the surface with her guns ready manned.

As Dick had said, one of the British destroyers was damaged. She was afire aft, and moving comparatively slowly. Her consort had slackened speed to assist her, and the five Huns were coming up fast.

The leading German spotted her and opened fire with her forward guns. Not bad shooting either, for the first salvo straddled her.

Guy had absolutely forgotten his wound. He was busy as a bee with his beloved electric.

'A bit in front of her, Penruddocke,' he said to the gunner. 'Let her run into it.'

Penruddocke had touched the button almost before the word was out of Mostyn's mouth. The two six-inch were barely a second later.

To Guy it seemed that all three shells burst simultaneously over the doomed destroyer, and though by this time he thought he knew all about neonite, the result was staggering.

The Hun ceased to be. Where one moment had been a keen-bowed ship tearing through the sea, the next there was nothing. A litter of fragments in a patch of oil. That was all. The destroyer, a craft of over a thousand tons, had been blotted out of existence.

Her consorts, appalled by the disaster, wheeled with one accord. The hindmost three were out of range, but the one that had been second in the line was still within five thousand yards.

Again the two six-inch guns of X1 roared out, and one shell at least reached its mark. A cloud of smoke arose, and when it cleared the German destroyer, a broken wreck, was sinking fast.

'Only wish we could get the rest of them,' replied Guy, eyeing the fugitives wistfully.

'Ahoy there, X1!' came a bellow across the sea. It was the uninjured British destroyer coming swirling up.

'Stapylton it is,' was the answer as the destroyer shot up alongside. 'And mighty glad to see you, Hallam.'

'Good for you, Mostyn,' he said heartily. 'You popped up just in the nick of time. We were in the soup pretty thick. My partner there, "Sybarite," had been pretty badly mauled. I say, lend me one of those guns of yours. I'd get the rest of the outfit, if you would.'

'Lend me your engines,' retorted Mostyn, with a laugh. 'Then I'll do the job myself. But it's no use. They're gone, and they won't come back. Come aboard and hear the tale of our adventures.'

'Too near Hunland, Mostyn. They'll have to keep till we get home. But I promise you, I'll believe anything after the way you mopped up that first chap. Now I must go and pick up survivors from that other craft. Afterwards I'll convoy you back.'

'You mean you'll let me take care of you all across the nasty wet North Sea,' retorted Mostyn.

'We'll talk about that when I come back. Meantime, you can dry-nurse "Sybarite." Push along, though, that's a good chap. I can catch you up.'

They meant to slip in quietly, tie up for the night, and have a good sleep. It was therefore rather embarrassing to be greeted by roars of cheers from a crowded sea front.

'It's that blighter, Stapylton!' growled Dick to Guy. 'He's wirelessed and given the show away.'

Late as it was, they had to come ashore. The Mayor himself met them. They were conducted to the best hotel and given an excellent dinner. Mostyn, much to his annoyance, had to make a speech. It was one in the morning before they got to bed. But, as Guy confessed, there was one consolation—the hotel spring mattresses were a vast improvement on X1's hard little bunks. He slept like the dead.

Next morning telegraphic orders arrived for Mostyn, Dick Anson, Mr Ingram, and Guy to present themselves with all speed at the Admiralty. At the station they found a special carriage reserved for them, and at Liverpool Street a splendid Rolls-Royce was in waiting.

'How do you like the "Conquering Hero" act?' whispered Dick in Guy's ear, as they took their seats.

'Penny for your thoughts, Guy,' grinned Dick. 'No, you needn't tell me. I know 'em.'

It was Sir Rupert Dayle himself who met them at the Admiralty, and with him was old Captain Karslake.

'Oh, haven't I? If you knew the sensation in Germany you would understand that I do not need to worry much about your report.'

'No,' replied the Admiral, 'but some one else has. Vassall returned across the frontier into Holland last night, and I had a long despatch from him first thing this morning. I tell you our enemies are simply appalled, and they have not been able to keep the matter dark, either. Neonite in action has simply paralysed them.

'And now,' he added, 'we must wait. We have another appointment to keep—and with a gentleman who is always punctual. Get into the car again.'

'One moment,' said Karslake. 'You've done me out of a dinner, but will a luncheon do instead?'

They all got into the Rolls-Royce again, the Admiral with them, but it was not until they turned into the Green Park that they realised their destination.

For Guy—for them all—the next half-hour was simply breathless. It was not until they were in the car again and being whirled back eastwards that even Dick recovered himself enough to talk.

'And I've got my commission,' Guy answered, in a voice that was curiously solemn.

'I shan't ever forget any of it so long as I live,' said Guy. 'It's been the most wonderful piece of luck that ever happened.' He paused.

'And it was all through you, Dick,' he added. 'If you hadn't come down at Claston, none of it would have happened.'

'If I'd come down anywhere else, I should have been either drowned or shot to small pieces by the kindly von Fromach,' said Dick. 'So unless we are going to form ourselves into a mutual admiration society, we'd better shut up and keep our energies for luncheon.'

THE END

T.C. BRIDGES

THE SECRET OF THE BALTIC

WITH FOUR OOLOUR PLATES BY DUDLEY TENNANT (1867-1952)

TABLE OF CONTENTS

LIST OF ILLUSTRATIONS

CHAPTER I THE MAN FROM THE SKY

CHAPTER II VON FROMACH'S SECOND TRY

CHAPTER III DICK ANSON'S STORY

CHAPTER IV AN UGLY SHOCK

CHAPTER V WAYLAID!

CHAPTER VI THE 'DUG-OUT'

CHAPTER VII THE FIRST SHELL

CHAPTER VIII STAPYLTON'S PROMISE

CHAPTER IX THE KIDNAPPING OF WALLACE INGRAM

CHAPTER X THE HUN OFFERS TERMS

CHAPTER XI FRESH TREACHERY

CHAPTER XII THE DETECTOR

CHAPTER XIII ON THE TRAIL

CHAPTER XIV IN THE STRAITS

CHAPTER XV DODGING A DEPTH CHARGE

CHAPTER XVI NOSING HOME

CHAPTER XVII A MORNING CALL

CHAPTER XVIII POISON GAS

CHAPTER XIX X1 SAILS

CHAPTER XX THE STRICKEN CRUISER

CHAPTER XXI GUY GOES OVERBOARD

CHAPTER XXII FACE TO FACE