THE BRAIN STEALERS OF MARS

by John W. Campbell, Jr.



CHAPTER I

imitation of Life

Rod Blake looked up with a deep chuckle. The sky of Mars was almost black, despite the small, brilliant sun, and the brighter stars and planets that shone visibly, Earth most brilliant of all, scarcely sixty million miles away.
	“They’ll have a fine time chasing us, back there, Ted.” He nodded toward the brilliant planet.
	Ted Penton smiled beatifically.
	“They’re probably investigating all our known haunts. It’s their own fault if they can’t find us—outlawing research on atomic power.”
	“They had some provocation, you must admit. Koelenberg should have been more careful. When a man takes off some three hundred square miles of territory spang in the center of Europe in an atomic explosion, you can’t blame the rest of the world for being a bit skittish about atomic power research.”
	“But they might have had the wit to see that anybody that did get the secret would not wait around for the Atomic Power Research Death Penalty, but would light out for parts and planets quite unknown and leave the mess in the hands of a lawyer till the fireworks quieted down. It was obvious that when we developed atomic power we’d be the first men to reach Mars, and nobody could follow to bring us back unless they accepted the hated atomic power and used it,” argued Blake.
	“Wonder how old Jamison Montgomery Palborough made out with our claims,” mused Penton. “He said he’d have it right in three months, and this is the third month and the third planet. We’ll let the government stew,
and sail on, fair friend, sail on. I still say that was a ruined city we saw as we landed.”
	“I think it was, myself, but I remember the way you did that kangaroo leap on your neck the first time you stepped out on the moon. You certainly saw stars.”
	“We’re professionals at walking under cockeyed gravities now. Moon
—Venus—”
	“Yes, but I’m still not risking my neck on the attitude of a strange planet and a strange race at the same time. We’ll investigate the planet a bit first, and yonder mudhole is the first stop. Come on.”
	They reached the top of one of the long rolling sand dunes and the country was spread out below them. It looked exactly as it had been from the last dune that they had struggled up, just as utterly barren, utterly bleak, and unendingly red. Like an iron planet, badly neglected and rusted.

	The mudhole was directly beneath them, an expanse of red and brown slime, dotted here and there with clumps of dark red foliage.
	“The stuff looks like Japanese maple,” said Blake.
	“Evidently doesn’t use chlorophyl to get the sun’s energy. Let’s collect a few samples. You have your violet-gun and I have mine. I guess it’s safe to split. There’s a large group of things down on the left that look a little different. I’ll take them while you go straight ahead. Gather any flowers, fruits, berries or seeds you see. Few leaves—oh, you know. What we got on Venus. General junk. If you find a small plant, put on your gloves and yank it out. If you see a big one, steer clear. Venus had some peculiarly unpleasant specimens.”
	Blake groaned. “You telling me. I’m the bright boy that fell for that pretty fruit and climbed right up between the stems of a scissor tree. Uhuh. I shoot ‘em down. Go ahead, and good luck.”
	Penton swung off to the ieft, while Blake slogged ahead to a group of weird-looking plants. They were dome-shaped things, three feet high, with a dozen long, drooping, sword-shaped leaves.
	Cautiously Blake tossed a bit of stone into the center of one. It gave off a mournful, drumming boom, but the leaves didn’t budge. He tried a rope on one leaf but the leaf neither stabbed, grabbed, nor jerked away, as he had half expected after his lesson with the ferocious plants of Venus. Blake pulled a leaf off, then a few more. The plant acted quite plant-like, which pleasantly surprised him.
	The whole region seemed seeded with a number of the things, nearly all about the same size. A ~few, sprinided here and there, were in various stages of development, from a few protruding sword-leaves, to little threeinch domes on up to the full-grown plant. Carefully avoiding the larger
ones, Rod plucked two small ones and thrust them into his specimen bag. Then he stood off and looked at one of the domes that squatted so dejectedly in the thick, gummy mud.
	“I suppose you have some reason for being like that, but a good solid tree would put you all in the shade, and collect all the sunlight going. Which is little enough.” He looked at them for some seconds picturing a stout Japanese maple in this outlandish red-brown gum.
	He shrugged, and wandered on, seeking some other plant. There were few others. Apparently this particular species throttled out other varieties very thoroughly. He wasn’t very anxious anyway; he was much more in~ terested in the ruined city they had seen from the ship. Ted Penton was cautious.
	Eventually Blake followed his winding footsteps back toward the s’hip, and about where his footsteps showed he’d gathered his first samples, he stopped. There was a Japanese maple there. It stood some fifteen feet tall, and the bark was beautifully regular in appearance. The leaves were nearly a quarter of an inch thick, and arranged with a peculiar regularity, as were the branches. But it was very definitely a Japanese maple.
	Rod Blake’s jaw put a severe strain on the hinges thereof. It dropped some three inches, and Blake stared. He stared with steady, blank gaze at that perfectly impossible Japanese maple. He gawked dumbly. Then his jaw snapped shut abruptly, and he cursed softly. The leaves were stirring gently, and they were not a quarter of an inch thick. They were paper thin, and delicately veined. Further, the tree was visibly taller, and three new branches had started to sprout, irregularly now. They sprouted as he watched, growing not as twigs but as fully formed branches extending themselves gradually. As he stared harder at them they dwindled rapidly to longer twigs, and grew normally.

	Rod let out a loud yip, and made tracks rapidly extending themselves toward the point where he’d last seen Ted Penton. Penton’s tracks curved off, and Rod steamed down as fast as Mars’ light gravity permitted, to pull up short as he rounded a corner of another sword-leaf dome clump. “Ted,” he panted, “come over here. There’s a—a—weird thing. A—it looks like a Japanese maple, but it doesn’t. Because when you look at it, it changes.”
	Rod stopped, and started back, beckoning Ted.
	Ted didn’t move.
	“I don’t know what to say,” he said quite clearly, rather panting, and sounding excited, though it was a quite unexciting remark, except for one thing. He said it in Rod Blake’s voice!
	Rod stiffened. Then he backed away hurriedly, stumbled over his feet and sat down heavily in the sand. “For the love of—Ted—Ted, wh-what did you s-s-say?”
	“I don’t know wh-what to s-s-say.”
	Rod groaned. It started out exactly like his own voice, changed rapidly while it spoke, and wound up a fair imitation of Ted’s. “Oh, Lord,” he groaned, “I’m going back to the ship. In a hurry.”
	He started away, then looked back over his shoulder. Ted Penton was moving now, swaying on his feet peculiarly. Delicately he picked up his left foot, shook it gently, like a man trying to separate himself from a piece of flypaper. Rod moved even more rapidly than he had before. Long, but rapidly shrinking roots dangled from the foot, gooey mud dropping from them as they shrank into the foot. Rod turned again with the violet-gun in his hand. It thrummed to blasting atomic energy, and a pencil beam of ravening ultra-violet fury shot out and a hazy bail of light surrounded
it.

	The figure of Ted Penton smoked suddenly, and a hole the size of a golf ball drove abruptly through the center of the head, to the accompaniment of a harsh whine of steam and spurts of oily smoke. The figure did not fall. It slumped. It melted rapidly, like a snow-man in a furnace, the fingers ran together, the remainder of the face dropped, contracted, and became horrible. It was suddenly the face of a man whose pouched and dulled eyes had witnessed and enjoyed every evil the worlds knew, weirdly glowing eyes that danced and flamed for a moment in screaming fury of deadly hate—and dissolved with the last dissolution of the writhing face.
	And the arms grew long, very long and much wider. Rod stood frozen while the very wide and rapidly widening arms beat up and down. The thing took off and flapped awkwardly away, and for an instant the last trace of the hate-filled eyes glittered again in the sun.
	Rod Blake sat down and laughed. He laughed, and laughed again at the very funny sight of the melting face on the bat-bodied thing that had flown away with a charred hole in the middle of its grape-fruit-sized head. He laughed even louder when another Ted-Penton-thing came around the corner of the vegetable clump, on the run. He aimed at the center of its head. “Fly away!” he yelled as he pressed the little button down.
	This one was cleverer. It ducked. “Rod—for the love of—Rod, shut up,” it spoke.
	Rod stopped, and considered slowly. This one talked with Ted Penton’s voice. As it got up again he aimed more carefully and flashed again. He wanted it to fly away too. It ducked again, in another direction this time, and ran in rapidly. Rod got up hastily and ran. He fell suddenly as some fibrous thing lashed out from behind and wrapped itself unbreakably about his arms and body, binding him helplessly.
	Penton looked down at him, panting heavily.
	‘What’s the trouble, Rod; and why in blazes were you shooting your gun at me?”
	Rod heard himself laugh again, uncontrollably. The sight of Ted’s worried face reminded him of the flying thing, with the melted face. Like an overheated wax figure. Penton reached out a deliberate hand and cracked him over the face, hard. In a moment Rod steadied, and Penton removed the noose from his arms and body. Blake sighed with relief.

	“Thank God, it’s you, Ted,” he said. “Listen, I saw you—you—not thirty seconds ago. You stood over there, and I spoke to you. You answered in my voice. I started off, and your feet came up out of the ground with roots on them, like a plant’s. I shot you through the forehead, and you melted down like a wax doll to a bat-thing that sprouted wings and flew away.”
	“Uhh—” said Penton soothingly. “Funny, at that. Why were you looking for me?”
	“Because there’s a Japanese maple where I was that grew while my back was turned, and changed its leaves while I looked at it.”
	“Oh, Lord,” said Penton unhappily, looking at Rod. Then more soothingly, “I think we’d better look at it.”
	Rod led the way back on his tracks. When the maple should have been in sight, it wasn’t at all. When they reached the spot where Rod’s tracks showed it should have been, it wasn’t there. There was only a somewhat wilted sword-bush. Rod stared blankly at it, then he went over and felt it cautiously. It remained placidly squatted, a slightly bedraggled lump of vegetation.
	“That’s where it was,” said Blake dully. “But it isn’t there any more. I know it was there.”
	“It must have been an—er—mirage,” decided Penton. “Let’s get back to the ship. We’ve had enough walking practice.”
	Rod followed him, wonderingly shaking his head. He was so wrapped up in his thoughts, that he nearly fell over Penton, when Ted stopped with a soft, unhappy, gurgling noise. Ted turned around and looked at Rod carefully. Then he looked ahead again.
	“Which,” he asked at length, “is you?”
	Rod looked ahead of Penton, over his shoulder. Another Rod was also standing in front of Penton. “My God,” said Rod, “it’s me this time!”
	“I am, of course,” said the one in front. It said it in Rod Blake’s voice.
	Ted looked at it, and finally shut his eyes.
	“I don’t believe it. Not at all. Wo bist du gewesen, mein Freund?”
	“Was sagst du?” said the one in front. “But why the Deutsch?”
	Ted Penton sat down slowly and thoughtfully. Rod Blake stared at Rod Blake blankly, slightly indignant.
	“Let me think,” said Penton unhappily. “There must be some way to tell. Rod went away from me, and then I come around the corner and find him laughing insanely. He takes a shot at me. But it looks, and talks like Rod. But he says crazy things. Then I go for a walk with him—or it—and meet another one that at least seems less insane than the first one. Well, well. I know German of course, and so does Rod. Evidently this thing can read minds. Must be like a chameleon, only more so.”
	‘~What do you mean?” asked Rod Blake. It doesn’t particularly matter which one.
	“A chameleon can assume any color it wants to at will. Lots of animals have learned to imitate other animals for safety, but it takes them generations to do it. This thing, apparently, can assume any shape or color at will. A minute ago it decided the best form for the locality was a swordbush. Some of these things must be real plants then. Rod thought of a maple tree, thought of the advantages of a maple tree, so it decided to try that, having read his mind. That was why it was wilted-looking; this isn’t the right kind of country for maple trees. It lost water too fast. So it went back to the sword-bush.
	“Now this one has decided to try being Rod Blake, clothes and all. But
I haven’t the foggiest notion which one is Rod Blake. It won’t do a bit
of good to try him on languages we know, because he can read our minds.
I know there must be some way. There must—there must—Oh yes. It’s
simple. Rod, just burn me a hole in that thing with your violet-gun.”
	Rod reached for his gun at once with a sigh of relief and triggered quickly. The phoney Rod melted hastily. About half of it got down into the boiling mud before Rod incinerated the rest with the intense ultraviolet flare of the pistol. Rod sighed. “Thank the Lord it was me. I wasn’t sure for a while, myself.”
	Ted shook himself, put his head in his hands, and rocked slowly. “By the Nine Gods of the Nine Planets, what a world! Rod, for the love of heaven, stay with me hereafter. Permanently. And whatever you do, don’t lose that pistoL They can’t grow a real violet-gun, but if they pick one up, may God help us. Let’s get back to the ship, and away from this damned place. I thought you were mad. My error. It’s just the whole bloody planet that’s mad.”
	“I was—for a while. Let’s move.”
	They moved. They moved hastily back across the sand dunes to the ship.
CHAPTER II

The Secret of the Thushol

	“They’re centaurs,” gasped Blake. “Will you look at that one over there
—a nice little calico. There’s a beautiful little strawberry roan. What people! Wonder why the city is so dilapidated, if the people are still here in some numbers. Set ‘er down, will you, Ted. They haven’t anything dangerous, or they’d have a better city.”
	“Uhmmm—I suppose that’s right. But I’d hate to have one of those fellows nudge me. They must weigh something noticeable, even here—about twelve hundred pounds back on Earth. I’m setting down in that square. You keep your hand on that ten-inch ion-gun while I step out.”
	The ship settled with a soft thumpf in the deep sandy dust of the ruined city square. Half a hundred of the centaurs were trotting leisurely up, with a grizzled old Martian in the lead, his mane sparse and coarse. Ted Penton stepped out of the lock.
	“Pholshth,” the Martian said after a moment’s inspection. He extended his hands out horizontally from his shoulders, palms upward and empty.
	“Friends,” said Ted, extending his arms in a similar gesture, “I am Penton.”
	“Fasthun Loshthu,” explained the centaur, indicating himself. “Penshun.”
	“He sounds like an ex-soldier,” came Blake’s voice softly. “Pension. Is he O.K.?”
	“I think so. You can leave that post anyway, and shut off the main atomics, start auxiliary B, and close the rooms. Lock the controls with the combination and come on out. Bring your ion-gun as well as your ultraviolet. Lock the lock doors.”
	“Blazes. I want to come out this afternoon. Oh well, O.K.” Blake went to work hurriedly and efficiently. It was some thirty seconds before he was through in the power room. He stepped eagerly into the lock.
	He stopped dead. Penton was on his back, moving feebly, the old centaur bent over him, with his long, powerful fingers fixed around the man’s throat. Penton’s head was shaking slowly back and forth on the end of his neck, in a loose, rather detached-looking way.
	Blake roared and charged out of the lock, his two powerful pistols hastily restored to his holsters. He charged out—and sailed neatly over the centaur’s back, underestimating Mars’ feeble grip. In an instant he was on his feet again, and returning toward his friend when a skillful left forefoot caught his legs, and sent him tumbling as the heavy bulk of an agile young centaur landed on his back. Blake turned; a smaller, lighter
body far more powerfully muscled. In a moment the Earthman broke the centaurs’ grip and started through the six or seven others that surrounded him.
	A grunted word of command dissolved the mêlée, and Blake stood up, leaping toward Penton.
	Penton sat on the ground, rocking slowly back and forth, his head between his hands. “Oh, Lord, they all do it here.”
	“Ted—are you all right?”
	“Do I sound it?” Penton asked unhappily. “That old bird just opened up my skull and poured a new set of brains in. Hypnotic teaching— a complete university education in thirty seconds—all done with hypnotism and no mirrors used. They have the finest education system. God preserve us from it.”
	“Shthuntho ishthu thiu loinal?” asked the old Martian pleasantly.
	“Ishthu psoth lonthul timul,” groaned Penton. “The worst of it is, it works. I know his language as well as I know English.” Suddenly he managed a slight grin. He pointed to Blake and said: “Blake omo phusthu ptsoth.”
	The old centaur’s lined, sparsely bearded face smiled like a pleased child’s. Blake looked at him uneasily.
	“I don’t like that fellow’s fa—” He stopped, hypnotized. He walked toward the old Martian with blank eyes and the grace of an animated tailor’s dummy. He lay down in sections, and the old Martian’s long, supple fingers circled his neck. Gently they massaged the back of his spine up to the base of his skull.
	Penton smiled sourly from where he sat. “Oh, you don’t like his face, eh? Wait and see how you like his system.”
	The centaur straightened. Slowly Blake sat up. His head continued to nod and weave in a detached sort of way, till he gingerly reached up, felt around for it and took it firmly in his hands. He rested his elbows on his knees.
	‘We didn’t both have to know his blasted language,” he managed bitterly at last. “Languages always did give me headaches anyway.”

	Penton watched him unsympathetically.
	“I hate repeating things, and you’ll find it useful, anyway.”
	“You are from the third planet,” the Martian stated politely.
	Penton looked at him in surprise, started up, then rose to his feet gingerly.
	“Get up slowly, Blake, I advise you for your own good.” Then to the Martian: ‘Why, yes. But you knew! How?”
	“My great-great grandfather told me of this trip to the third planet before he died. He was one of those that returned.”
	“Returned? You Martians have been to Earth?” gasped Blake.
	“I guessed that,” said Penton softly. “They’re evidently the centaurs of legend. And I think they didn’t go alone from this planet.”
	“Our people tried to establish a colony there, many, many years ago. It didn’t succeed. They died of lung diseases faster than they could cross space. The main reason they went in the first place was to get away from the thushol. But the thushol simply imitated local Earth-animals and thrived. So the people came back. We built many ships, hoping that since we couldn’t go, the thushol would. But they didn’t like Earth.” He shook his head sorrowfully.
	“The thushol. So that’s what you call ‘em.” Blake sighed. ‘They must be a pest.”
	“They were then. They aren’t much any more.”
	“Oh, they don’t bother you any more?” asked Penton.
	“No,” said the old centaur apathetically. “We’re so used to them.”
	“How do you tell them from the thing they’re imitating?” Penton asked grimly. “That’s what I need to know.”
	“It used to bother us because we couldn’t,” Loshthu sighed. “But it doesn’t any more.”
	“I know—but how do you tell them apart? Do you do it by mindreading?”
	“Oh, no. We don’t try to tell them apart. That way they don’t bother us any more.”
	Penton looked at Loshthu thoughtfully for some time. Blake rose gingerly, and joined Penton in his enwrapped contemplation of the grizzled Martian. “tJhmmmm,” said Penton at last, “I suppose that is one way of looking at it. I should think it would make business rather difficult though. Also social relations, not knowing whether it was your wife or just a real good imitation.”
	“I know. We found it so for many years,” Loshthu agreed. “That was why our people wanted to move to Earth. But later they found that three of the ship commanders were thushol, so the people came back to Mars where they could live at least as easily as the thus hol.”
	Penton mentally digested this for some moments, while the half hundred centaurs about stood patiently, apathetically motionless.
	“We have myths on Earth of centaurs, people like you, and of magic creatures who seemed one thing, but when captured became snakes or tigers or other unpleasant beasts, but if held long enough reverted to human shape and would then grant a wish. Yes, the thushol are intelligent; they could have granted a simple Earth barbarian’s wish.”
	Loshthu shook his head slowly.
	“They are not intelligent, I believe. Maybe they are. But they have perfect memories for detail. They would imitate one of our number, at-
tend our schools, and so learn all we knew. They never invented anything for themselves.”
	‘What brought about the tremendous decline in your civilization? The thus hol?”
	The centaur nodded.
	‘We forgot how to make space ships and great cities. We hoped that would discourage the thushol so they would leave us. But they forgot too, so it didn’t help.”
	“Good Lord,” Blake sighed, “how in the name of the Nine Planets do you live with a bunch like that?”
	Loshthu looked at Blake slowly.
	“Ten,” he said. “Ten planets. You can’t see the tenth with any practicable instrument till you get out beyond Jupiter. Our people discovered it from Pluto.”

	Blake stared at him owlishly. “But how can you live with this gang? With a civilization like that—I should think you’d have found some means of destroying them.”
	‘We did. We destroyed all the thushol. Some of the thushol helped us, but we thought that they were our own people. It happened because a very wise, but very foolish philosopher calculated how many thushol could live parasitically on our people. Naturally the thushol took his calculations to heart. Thirty-one percent of us are thus hol.”
	Blake looked around with a swiftly unhappy eye.
	“You mean—some of these here are thushol?” he asked.
	Loshthu nodded.
	“Always. They reproduced very slowly at first, in the form of an animal that was normally something like us, and reproduced as did other animals. But then they learned to imitate the amc~lxe when they studied in our laboratories. Now they simply split. One big one will split into several small ones, and each small one will eat one of the young of our people, and take its place. So we never know which is which. It used to worry us.” Loshthu shook his head slowly.
	Blake’s hair rose slightly away from his head, and his jaw dropped away. “My God,” he gasped. “Why didn’t you do something?”
	“If we killed one we suspected, we might be wrong, which would kill our own child. If we didn’t, and just believe it our own child anyway, it at least gave us the comfort of believing it. And if the imitation is so perfect one can’t tell the difference, what is the difference?”
	Blake sat down again, quietly.
	“Penton,” he sighed, at length, “those three months are up, let’s get back to Earth—fast.”
	Penton looked at him. “I wanted to a long time back. Only I thought
of something else. Sooner or later, some other man is going to come here with atomic power, and if he brings some of those thushol back to Earth with him, accidentally, thinking it’s his best friend—well, I’d rather kill my own child than live with one of those, but I’d rather not do either. They can reproduce as fast as they can eat, and if they eat like an amceba
—God help us. If you maroon one on a desert island, it will turn into a fish, and swim home. If you put it in jail it will turn into a snake and go down the drain pipe. If you dump it in the desert it will turn into a cactus and get along real nice, thank you.”
	“Good God.”
	“And they won’t believe us, of course. I’m sure as blazes not going to take one back to prove it. I’ll just have to get some kind of proof from this Loshthu.”
	“I hadn’t thought of that. What can we get?”
	“All I can think of is to see what they can let us have, then take all we can, and make a return trip with reputable and widely believed zoologists and biologists to look into this thing. Evolution has produced some weird freaks, but this is a freakier weirdness than has ever been conceived.”
	“I still don’t really believe it,” Blake said. “The only thing I am firmly convinced of is my headache.”

	“It’s real enough and logical enough. Logical as hell. And hell on Earth if they ever get there. Evolution is always trying to produce an animal that can survive anywhere, conquer all enemies, the fittest of, the surviving fit. All life is based on one thing: protoplasm. Basically, it’s the same in every creature, every living thing, plant and animal, am~ba and man. It is just modified slightly, hooked together in slightly different ways. The thushol are built of protoplasm—but infInitely more adaptable protoplasm. They can do something about it, make it take the form of a bone cell and be part of a thigh bone, or be a nerve cell in a brain. From some of that ten-second-college-course Loshthu poured into me, I gather that at first the thushol were good imitations outside, but if you cut into one, you could see that the organs weren’t there. Now they have everything. They went through Martian medical colleges, of course, and know all about what makes a centaur tick, and so they make themselves with the same kind of tickers. Oh, very nice.”
	‘They don’t know much about us. Maybe with the X-ray fluoroscope screen we could have told those imitations of us,” suggested Blake.
	“Oh, no, by no means. If we knew the right form, they’d read it in our minds, and have it. Adaptive protoplasm. Just think, you couldn’t kill it in an African jungle, because when a lion came along, it would be a little, lady lion, and when an elephant showed up, it would be a helpless baby elephant. If a snake bit it, I suppose the damned thing would
turn into something immune to snake bites—a tree, or something like that. I just wonder where it keeps the very excellent brain it evidently has.”
“Well, let’s find out what Loshthu can offer us by way of proofs.”


CHAPTER III

Mind-Readers and Company

	It developed that the Martians had once had museums. They still had them, because nobody was sufficiently interested to disturb their age-long quiet. Martians lived centuries, and their memories were long; but once or twice in a lifetime did a Martian enter the ancient museums.
	Penton and Blake spent hours in them, intensive hours under Loshthu’s guidance. Loshthu had nothing but time, and Penton and Blake didn’t want to linger. They worked rapidly, collecting thin metal sheaves of documents, ancient mechanisms, a thousand things. They baled them with rope that they had brought from the ship when they moved it nearer the museum. Finally, after hours of labor, bleary-eyed from want of sleep, they started out again to the ship.
	They stepped out of the gloomy dusk of the museum into the sun-lit entranceway. Immediately, from behind a dozen pillars, a leaping, flashing group of men descended upon them, tore the books, the instruments, the data sheaves from their hands. They were upset, slugged, trampled on and spun around. There were shouts and cries and curses.
	Then there was silence. Twelve Pentons and thirteen Blakes sat, lay or stood about on the stone stairway. Their clothes were torn, their faces and bodies bruised, there was even one black eye, and another developing swiftly. But twelve Pentons looked exactly alike, each clasping a bit of data material. Thirteen Blakes were identical, each carrying a bit of factual mustiness under his arm or in his hand.
	Loshthu looked at them, and his lined, old face broke into a pleased smile. “Ah,” he said. “There are more of you. Perhaps some can stay with us to talk now.”
	Penton looked up at Loshthu, all the Pentons did. Penton was quite sure he was the Penton, but he couldn’t think of any way to prove it. It was fairly evident that thushol had decided to try Earth again. He began to wonder just—”
	“Loshthu, just why,” asked one of the Pentons in Penton’s voice, “did the thushol not stay on Earth if they could live there?”
Penton was quite sure he had been the one to think of that panic— ‘Pardon me, but wasn’t that the question I was going to ask?” said an-
other Penton in well-controlled fury. Penton smiled gently. It seemed evident that— “I can apparently be spared the trouble of doing my own talking. You
all help so,” said one of the numerous Pentons angrily.
	“Say, how in hell are we going to tell who’s who?” demanded one of the Blakes abruptly.
	“That damned mind-thief stole my question before I had a chance—”
	“Why you—you—you talking! I was just about—”
	“I think,” said one of the Pentons wearily, “you might as well stop getting peeved, Blake, because they’ll all act peeved when you do. What do you know. I beat all my imitators to the draw on that remark. A noble achievement, you’ll find, Rod. But you might just as well pipe down, and I’ll pipe down, and we’ll see what our good friend, Loshthu, has to say.”
	“Eh,” sighed Loshthu. “You mean about the thushol leaving Earth? They did not like it. Earth is a poor planet, and the people were barbarians. Evidently they are not so now. But the thushol do not like work, and they found richer sustenance on Mars.”

	“I thought so,” said Penton. (Does it matter which one?) “They’ve decided that Earth is richer than Mars now, and want a new host. Don’t draw that pistol, Blake! Unfortunately, my friend, we had twenty-five ionguns and twenty-five violet-guns made up. If we’d had more we would have more companions. We were exceedingly unfortunate in equipping ourselves so well in the matter of clothing, and being so. thoughtful as to plan all of it right, so we carried a lot of each of the few kinds. Exceedingly. However, I think we can improve things a little bit. I happen to remember that one ion-gun is out of commission, and I had the coils out of two of the violet-guns to repair them. That makes three guns out of service. We will each stand up and fire, one at a time, at the sand in front there. The line forms on the right.”
	The line formed. “Now,” continued that particular Penton, “we will each lire, beginning with myself, one at a time. First ion, then violet. When one of us evidences lack of a serviceable gun, the others will join in removing him rapidly but carefully. Are we ready? Yes?” That Penton held up his ion-gun, and pushed the button.
	It didn’t fire, and immediately the portico stank with his smoke.
	“That’s one,” said the next Penton. He raised his ion-gun and fired.. Then his violet-gun. Then he raised it and fired again, at a rapidly dissolving Blake. “That makes two. That one evidently found, when we fired at the first one, that his didn’t work. We have one more to eliminate. Next?”
	Presently another Blake vanished. ‘Well, well,” said Penton pleasantly, “the Blake-Penton odds are even. Any suggestions?”
	“Yes,” said Blake tensely. “I’ve been thinking of a patch I put in one suit that I ripped on Venus.” Another Blake vanished under the mutual fire.
	‘There’s one more thing I want to know. Why in blazes are those phonies so blasted willing to kill each other, and though they know which is which, don’t kill us? And how did they enter the ship?” Rod demanded. Or at least a Rod.
	“They,” said two Pentons at once. Another one looked at them. “Bad timing, boys. Rodney, my son, we used a combination lock. These gentlemen are professional mind-readers. Does that explain their possession of the guns? I’ve been thinking right along of one way to eliminate these excessive excrescences, consisting of you going into a huddle with your tribe, and eliminating all but the one you know to be yourself, and I doing the same. Unfortunately, while they’re perfectly willing to kill each other so long as they don’t die, they will prevent their own deaths by adequate, unfortunately adequate defense.
	“Now since these little gun tests and others have been made I think it fairly evident that we are not going to leave this planet until the two right men are chosen and only two go into that ship with us. Fortunately they can’t go without us, because while they can read minds, it takes more than knowledge to navigate a space ship, at least such knowledge as they can get from us. It takes understanding, which mere memory will not supply. They need us.
	“We will, therefore, march dutifully to the ship, and each of us will replace his guns carefully in the prepared racks. I know that I’m the right Penton—but you don’t. So no movement will be made without the unanimous agreement of all Pentons and Blakes.”
	Blake looked up, white-faced.
	“If this wasn’t so world-shakingly serious, it would be the damnedest comic opera that ever happened. I’m afraid to give up my gun.”
	“If we all give them up, I think it puts us even. We have some advantage in that they don’t want to kill us, and if worst comes to worst, we could take them to Earth, making damned sure that they didn’t get away. On Earth we could have protoplasmic tests made that would tell the story. By the way, that suggests something. Yes indeed, I think we can make tests here. Let us repair to this ship.”
CHAPTER IV

Penton’s Strategy

	The Blakes sat down and stayed down. “Ted, what in blazes can we do?” His voice was almost tearful. “You can’t tell one of these ghastly things from another. You can’t tell one from me. We can’t—”
	“Oh, God,” said another Blake, “that’s not me. That’s just another one of those damned mind stealers.”
	Another one groaned hopelessly.
	‘That wasn’t either.” They all looked helplessly at the line of Pentons. “I don’t even know who’s my friend.”
	Fenton nodded. All the Pentons nodded, like a grotesquely solemn chorus preparing to recite some blessing. They smiled in superhuman unity. “That’s all right,” they said in perfect harmony. ‘Well, well. A new stunt. Now we all talk together. That makes things easier. I think there may be a way to tell the difference. But you must absolutely trust me, Blake. You must give up your guns, putting all faith in my ability to detect the right one, and if I’m wrong, realize that I will not know. We can try such simple tests as alcohol, whiskey, to see if it makes them drunk, and pepper to see if it bums their tongues—”
	“It won’t work,” said Blake tensely. “Lord, Penton, I can’t give up my guns—I won’t—”
	Penton, all the Pentons smiled gently. “I’m half again ‘as fast as you are, Blake, and no Martian-born imitation of you is going to be faster. Maybe these Martian imitations of me are as fast as I am. But you know perfectly well that I could ray the whole gang of you, all ten of you, out of existence before any one of you could move a finger. You know that, don’t you, Rod?”
	“Lord, yes, but Ted, Ted, don’t do that—don’t make me give up my guns—I’ve got to keep them. Why should I give up mine, if you keep yours?”
	“That probably was not you speaking, Rod, but it doesn’t matter. If it wasn’t what you thought, we could do something about it. Therefore, that is what you wanted to say, just as this is what I wanted to say, whether I said it or not. Oh, Lord preserve us. It talks with my voice! But anyway, the situation is this; one of us has to have unquestioned superiority over the other gang. Then, the one with the whip hand can develop proof of identity, and enforce his decisions. As it is, we can’t.”
	“Let me be that one, then,” snapped one Blake.
	“I didn’t mean that,” sighed another. “That wasn’t me.”
	“Yes it was,” said the first. “I spoke without thinking. Go ahead. But
how are you going to make the others give up their guns? I’m willing. You can’t make them?”
	“Oh, yes I can. I have my faithful friends, here,” said Penton grimly, his eleven hands waving to his eleven counterparts. ‘They agree with me this far, being quite utterly selfish.”
	“But what’s your system. Before I put my neck in the noose, I have to know that noose isn’t going to tighten on it.”
	“If I had a sound system in mind—I’m carefully refraining from developing one—they’d read it, weigh it, and wouldn’t agree at all. They still have hopes. You see that pepper and alcohol system won’t work perfectly because they can read in my mind the proper reaction, and be drunk, or have an inflamed tongue at will, being perfect actors. I’m going to try just the same. Rod, if you ever trusted me, trust me now.”
	“All right, come on. We’ll go to the ship, and any one of these things that doesn’t part with its gun is not me. Ray it.”
	Blake rose jerkily, all ten of him, and went down to the ship.
	The Pentons followed faithfully after. Abruptly Penton rayed one Blake. His shoulder blades had humped curiously and swiftly. Wings were developing. ‘That helps,” said Penton, holstering his guns.
	The Blakes went on, white-faced. They put the weapons in the racks in the lock stoically. The Martians had seen the, to them, inconceivably swift movements of Penton’s gun hands, and Penton knew that he, himself, had done the raying that time. But he still didn’t know a way to prove it without causing a general mêlée which would bring about their own deaths. That wasn’t so important. The trouble was that given fifty years, the rest of the world would descend on this planet unwamed. Then all Earth would be destroyed. Not with flame and sword and horrible casualty lists, but silently and undetectably.
	The Blakes came out, unarmed. They shuffled and moved about uneasily, tensely, under the watchful eyes of eleven Pentons armed with terrifically deadly weapons.
	Several Pentons went into the ship, to come out bearing pepper, saccharine tablets, alcohol, the medicine chest. One of them gathered them together and looked them over. “We’ll try pepper,” he said, rather unhappily. “Line up!”
	The Blakes lined up, hesitantly. “I’m putting my life in your hands, Ted,” said two of them in identical, plaintive tones.
	Four Pentons laughed shortly. “I know it. Line up. Come and get it.”
	“First,” he sighed, after a moment, “stick out the tongue, patient.”
	With unsteady hands he put a bit of pepper from the shaker on the fellow’s tongue. The tongue snapped in instantly, the Blake clapped his hands to his mouth, gurgling unpleasantly. ‘Waaaar!” he gasped. “Waar— achooo—damnt!”
	With hands like flashing light, Penton pulled his own, and a neighbor’s ion-gun. In a fiftieth of a second all but the single gagging, choking, coughing Blake were stinking, smoking, swiftly dissolving and flowing rubbish. The other Penton methodically helped destroy them.
	Blake stopped gagging in surprise.
	“My God, it might not have been the right one!” he gasped.
	The ten Pentons sighed softly. “That finally proves it. Thank God. Definitely. That leaves me to find. And it won’t work again, because while you can’t read my mind to find the trick that told, these brothers of mine have. The very fact that you don’t know how I knew, proves that I was right.”
	Blake stared at him dumbly. “I was the first one—” he managed between a cough and a sneeze.
	“Exactly. Go on inside. Do something intelligent. Use your head. See what you can think of to locate me. You have to use your head in some such way that they don’t mind-read it first, though. Go ahead.”
	Blake went, slow-footed. The first thing he did was to close the lockdoor, so that he was safely alone in the ship. Blake went into the control room, donned an air-suit complete with helmet, and pushed a control handle over. Then a second. Presently he heard curious bumpings and thumpings, and strange floppings and whimperings. He went back rapidly, and rayed a supply chest and two crates of Venusian specimens that had sprouted legs and were rapidly growing arms to grasp ray pistols. The air in the ship began to look thick and greenish; it was colder.
	Contentedly Blake watched, and opened all the room doors. Another slithering, thumping noise attracted him, and with careful violet-gun work he removed an unnoticed, extra pipe that was crawling from the crossbrace hangers. It broke up into lengths that rolled about unpleasantly. Rod rayed them till the smallest only, the size of golf balls with curious blue-veined legs, staggered about uncertainly. Finally even they stopped wriggling.
	Half an hour Rod waited, while the air grew very green and thick. Finally, to make sure, he started some other apparatus, and watched the thermometer go down, down till moisture grew on the walls and became frost, and no more changes took place. Then he went around with an opened ion-gun with a needle beam and poked everything visible with
it.

	The suction fans cleared out the chlorine-fouled atmosphere in two minutes, and Blake sat down wearily. He ffipped over the microphone switch and spoke into the little disc. “I’ve got my hand on the main ion-gun control. Penton, I love you like a brother, but I love Earth more. If you can induce your boy friends to drop their guns in a neat pile and retire—
0. K. If not, and I mean if not within thirty seconds, this ion-gun is going into action and there won’t be any more Pentons. Now, drop!”
	Grinning broadly, with evident satisfaction, ten Pentons deposited twenty heart-cores of ultra-essence of destruction, and moved off. “Way off,” said Blake grimly. They moved.
	Blake collected twenty guns. Then he went back into the ship. There was a fine laboratory at one end, and with grim satisfaction, he took down three cotton-stoppered tubes, being very careful to handle them with rubber gloves. “You never did man a good turn before, tetanus, but I hope you spread high, wide and handsome here—”
	He dumped them into a beaker of water, and took beaker and glass down to the lock and out. The ten waited at a distance.
	“All right, Penton. I happen to know you took a shot of tetanus antivaccine some while ago, and are immune. Let’s see if those blasted brain stealers can steal the secret of something we know how to make, but don’t know anything about. They can gain safety by turning into a chicken, which is immune, but not as human creatures. That’s a concentrated dose of tetanus. Go drink it. We can wait ten days if we have to.”
	Ten Pentons marched boldly up to the beaker, resting beside the ship. One stepped forward to the glass—and nine kept right on stepping. They stepped into the lee of the ship where the ion-gun could not reach.
	Blake helped Penton into the ship with a broad grin.
	“Am I right?”
	“You’re right,” sighed Penton, “but God knows why. You can’t get tetanus by swallowing it, and lockjaw doesn’t develop so quickly as ten days.”
	“I didn’t know for sure,” grinned Blake. ‘They were too busy trying to find out what I was doing to follow your mind. Ah—there they go. Will you ray them or shall I?” asked Blake politely, sighting the ion-gun at the nine flapping, rapidly vanishing things scuttling across the red, rusty planet. The ship dipped sharply in pursuit. “There’s one thing—ahhh—” he straightened as the incredible glare died in thin air. “I want to know. How in blazes did you pick me out?”
	“To do what you did requires some five hundred different sets of muscles in a beautifully coordinated neuromuscular hookup, which I didn’t believe those things could imitate without a complete dissection. I took the chance it was you.”
	“Five hundred sets of muscles! What the heck did I do?”
	“You sneezed.”
	Rod Blake blinked slowly, and slowly his jaw tested again its supports and their flexibility.