A mysterious cloud drifts menacingly through space...
A sudden energy flash and the Doctor is infected with the
Nucleus of a malignant Virus that threatens to destroy his
mind.
Meanwhile, on Titan, human slaves prepare the Hive from
which the Virus will swarm out and infect the universe.
In search of a cure, Leela takes the Doctor to the
Foundation where they make an incredible journey into
the Doctor's brain in an attempt to destroy the Nucleus.
But can the Doctor free himself from the Nucleus in time
to reach Titan and destroy the Hive? Luckily he has help -
in the strangely dog-like shape of a mobile computer
called K9...

ISBN 0 426 20054 3
             DOCTOR WHO
               AND THE
           INVISIBLE ENEMY
  Based on the BBC television serial The Invisible Enemy by Bob
Baker and Dave Martin by arrangement with the British Broadcasting
                           Corporation




                TERRANCE DICKS




                          published by
                    The Paperback Division of
                     W. H. Allen & Co. Ltd
A Target Book
Published in 1979
by the Paperback Division of W. H. Allen & Co. Ltd.
A Howard & Wyndham Company
44 Hill Street, London W1X 8LB

Copyright © 1979 by Terrance Dicks, Bob Baker and Dave Martin
'Doctor Who' series copyright © 1979 by the British Broadcasting
Corporation

Printed in Great Britain by
Richard Clay (The Chauncer Press) Ltd, Bungay, Suffolk

ISBN 0 426 20054 3

This book is sold subject to the condition that it shall not, by way of
trade or otherwise, be lent, re-sold, hired out or otherwise circulated
without the publisher's prior consent in any form of binding or
cover other than that in which it is published and without a similar
condition including this condition being imposed on the subsequent
purchaser.
CONTENTS

1 Contact
2 The Host
3 Death Sentence
4 Foundation
5 Counter-Attack
6 The Clones
7 Mind Hunt
8 Interface
9 Nucleus
10 The Antidote
11 The Hive
12 Inferno
                               1
                             Contact
      Something was waiting out in space.
      It drifted between the stars, formless, shapeless, a hazy, drifting
cloud, waiting patiently, as it had waited for millennia. It was
helpless since it lacked physical form, yet potentially it was all-
powerful. Apparently inert, it was filled with life and a fierce, driving
purpose. It was waiting for a host.

        The space shuttle nosed its way through the asteroid belt,
altering course to avoid the larger ones, deflecting the smaller with its
energy shields. Inside the little control cabin, the bored three-man
crew waited for the long voyage to end.
        Meeker was at the controls, staring moodily at the instrument
panels. Behind him the captain, Safran, and Silvey, the other crew
member, lay on their acceleration couches. Safran was dozing, his
worn features relaxed in sleep. Silvey, young and fresh-faced, was
awake and restless.
        Technically, Meeker was on duty, though in reality he had
nothing to do. A steady, self-satisfied instrument-beep announced
that the ship's computer was really in charge. It had brought the ship
from Earth, soon it would land it safely on Titan, one of the ten
moons that circled the giant planet Saturn, 1,430 million kilometres
from Earth's sun. This was the paradox of space travel. You selected
the brightest, the most determined from thousands of candidates and
trained them to a peak of mental and physical skill. Then you
surrounded them with computer technology so that only in some
million-to-one emergency would their skills ever be needed.
        The space radar screen was filled with the blips that marked the
track of the asteroids. A particularly large one appeared; the ship
tilted in an emergency course-correction.
        Meeker decided to stage his own little rebellion. His hands
moved over the controls. Silvey looked up. 'What are you doing?'
        'Going over to manual.'
       'What for?'
       'Why not? If I'm going to be banged around, I'd sooner do it
myself!' Meeker flicked on the forward scanner and began steering a
course through the asteroids, throwing the little ship about in his
enthusiasm.
       Silvey yawned. 'It's still telling you what to do...'
       'Yes, but at least I'm doing it!'
       A sudden lurch nearly sent Silvey from his acceleration couch.
'Oh, come on, Meeker...'
       A second, and even more violent lurch produced a steady,
reproachful beep from the watchful computer. Captain Safran opened
one eye. 'You're off course, Meeker.'
       Meeker wrestled with the controls. 'Sorry, Skipper.'
       'Put it back on automatic, Meeker—please.'
       Still struggling to complete his course correction, Meeker
muttered, 'I can't...' He felt a sudden flare of panic as the computer
failed to respond. It was as if something had distracted its attention.
       Safran got to his feet, leaned over the console and stabbed
rapidly at the controls. The alarm signal ceased, there was a musical
beep, and the controls locked back on to automatic.
       Safran said, 'Titan shuttle captain to computer.'
       A musical tone acknowledged his self-identification. 'New
course for Titan, please.'
       A beep of assent. Lights flashed on the keyboard,.and the
shuttle adjusted its course.
       Safran put a hand on Meeker's shoulder. 'All right, Meeker,
that's enough. You're off watch. At once, please.'
       Meeker took Safran's place on the couch, while Safran slid
easily into the command chair. Automatically he began checking his
instruments.

       The shuttle was almost through the asteroid belt by now, and
the drifting cloud was waiting. As the shuttle approached, the cloud
flickered with energy, as if it sensed the presence of approaching life.
It thickened, condensed, and began moving purposefully towards the
shuttle.
       Safran said reproachfully, 'You've lost us three minutes,
Meeker!'
       'So? Going to be there six months, aren't we?'
       'That's not the point! '
       'Sorry, Skipper. The thought of six months on Titan...'
       'What's wrong with it?' asked Silvey cheerfully. 'Routine
duties, easy life...'
       Meeker nearly exploded. 'I qualified for exploration eight years
ago, and what am I? Glorified garage attendant on a planetary filling
station!'
       Silvey grinned sympathetically. Actually there was some point
to Meeker's complaint. But Space Service rules were strict. Everyone
had to accept his share of the routine duties, as well as the more
exciting and glamorous assignments.
       'Your turn'll come,' said Safran consolingly. 'And you'll be glad
enough of refuelling bases then.'
       Meeker refused to be consoled. 'All I'm saying is why take a
real space pilot and—'
       An alarm-beep from the computer interrupted him.
       'Unidentified organism approaching,' said the computer.
'Changing course to avoid.'

       The shuttle veered away from the approaching space cloud. But
as it brushed the edge, something within the nebulous mass flared
into life, and sent out a fiery tentacle. Lightning flickered around the
shuttle for a moment, then died away.
       The shuttle moved on, and the cloud began drifting away
through space...

      Safran stared at the empty radar screen. 'What was all that
about? There's nothing there... Titan shuttle captain. Report please.'
      In a slurred, dragging voice the computer said, 'Contact has
been made...'
      Safran looked at his two crew members. 'Contact?' he said
wonderingly. 'What does that mean?' No one answered him.
       Meanwhile another craft was on its way to the same remote
edge of the solar system, travelling through the vortex, that
mysterious region where space and time are one. It was called the
TARDIS and the outside of it resembled an old blue police-box. The
inside was a very different matter. The TARDIS was dimensionally
transcendental—bigger on the inside than the outside. How much
bigger was difficult to say, but an astonishing number of rooms were
tucked away inside.
       A very tall man with a mop of curly hair marched into one of
the control rooms and stood gazing around with an expression of
mild displeasure. He was dressed with a kind of casual Bohemian
elegance in a long, loose jacket, gaily checked waistcoat and tweed
trousers. The outfit was topped with a broad-brimmed soft hat, and an
incredibly long multi-coloured scarf dangled round his neck.
       The girl who followed him into the control room wore a brief
outfit made from animal skins. She moved with panther-like grace
and her hand was never far from the knife in her belt. Leela had been
brought up as a fighting warrior in a tribe that had regressed from
technological civilisation to primitive savagery. She had been the
Doctor's companion for some time, and she should have been used to
scientific marvels by now—but the TARDIS could still surprise her.
       Leela gazed wonderingly around the control room.
       It seemed very like the TARDIS control room she was used to,
the same many-sided console in the centre. But there was one major
difference. This control room was all in gleaming white. Leela looked
at the Doctor. 'We've never been here before.'
       'You've never been here before,' said the Doctor moodily. He
crossed to the console, removed a side-panel and began checking
something inside.
       'Where are we?' asked Leela curiously.
       'Number two control room. It's been closed for redecoration.'
The Doctor glared at the console. 'I don't like the colour,' he said
accusingly.
       'White isn't a colour,' objected Leela.
       The Doctor said, 'That's the trouble with computers, always
thinking in black and white. No aquamarines, no blues. No
imagination!'
       Leela gathered that the TARDIS had the power to redecorate
itself on its own initiative. She was about to ask the Doctor why he
didn't just order the redecoration to be changed, when the control
room gave a sudden lurch. 'Have we stopped?'
       'No, we haven't stopped.'
       'Have we materialised?'
       'Yes.' The Doctor flicked on the scanner. Somewhere in the
distance a huge planet hung in space. It was surrounded by a shining
ring, a kind of halo.
       Leela looked at the screen. 'Where are we, Doctor?'
       The Doctor studied instrument-readings. 'The edge of Earth's
solar system, somewhere near Saturn... about 5,000 AD.' He looked
at Leela. '5,000 AD, Leela! We're in the time of your ancestors.'
       'Ancestors?' Leela's tribe, the Sevateem, were the descendants
of a planetary survey team who had been stranded on a hostile planet.
       ''That's right. That was the time of the great break-out!'
       'The great what?'
       The Doctor stared abstractedly at the ringed planet on the
scanner. 'The time when your forefathers went leapfrogging across
the solar system on their way to the stars. The asteroid belt's probably
teeming with them by now. Frontiersmen, pioneers, waiting to spread
across the galaxy like a tidal wave—or a disease...'
       'Why a disease—I thought you liked humanity?'
       'I do, I do,' protested the Doctor. 'Some of my best friends are
human. But when they get together in great numbers, other life-forms
sometimes suffer...'

        Saturn is a giant of a planet, an immense globe of gas seven
hundred and fifty times the volume of Earth. Besides its famous
'rings', formed by countless icy particles reflecting the dim sunlight,
Saturn is celebrated for the number of its moons. There are ten in all,
and the largest, Titan, is the biggest satellite in the solar system.
Larger than the planet Mercury, it has its own cloudy atmosphere of
hydrogen and methane. It was on Titan that the Earthmen had built
their refuelling base. Giant fans sucked the hydrogen/methane
atmosphere through enormous intake shafts, into the station's storage
tanks where it was processed and converted into chemical booster
fuel. The station itself was bleakly functional, its machinery and
living quarters embedded deep in solid rock. It was a place of
winding tunnels and metal corridors festooned with miles of
sprawling gas-pipes. Here the crew of the shuttle craft were to live, or
at least exist, for the next six months, relieving the three-man crew
already there.
       The space shuttle drifted into the station docking bay and
locked on, the whole operation master-minded by the computer.
There was a clang and a hiss as the ship's airlock connected with the
tunnel that led into the base.
       In the control cabin the computer said, 'Docking complete.
Ship locked-on.'
       The three crewmen were pulling on their helmets and space
gauntlets, moving in uncanny unison, as though under the direction
of a single mind. Safran went over to the arms locker, and took out
three hand-blasters. He passed two to Meeker and Silvey, and kept
the third for himself. He slipped the blaster into the thigh-pocket of
his space-suit and the others did the same.
       Safran led them to the airlock door and swung it open.
       They moved through the little tunnel, Safran opened another
door and they emerged into a metal corridor.
       A cheerful voice came from a near-by loudspeaker. 'Are we
glad to see you! Welcome to Titan—and you're welcome to it!' The
voice paused as if expecting some answer. Safran, Meeker and Silvey
stood motionless, waiting. The only sound was the strangely hoarse
breathing from beneath their helmets. After a moment, the voice went
on, 'Well, we're all in the mess, celebrating. Come and join us.'
       The corridor led to a wider one, broader and better lit, and that
in turn led to an open area with two metal doors. One was marked
Crew Mess Room. From behind it came laughter and a babble of
cheerful talk. The soon-to-be-relieved crew were celebrating their
departure. Safran moved to the other door and opened it. Sleeping
quarters, neat and empty, blankets folded, a bulging travel-pack on
the end of each bunk. The Titan crew were packed and ready to go.
       Safran closed the door and moved back to the mess. He drew
the blaster from his pocket, and the two others did the same.
       He touched a control-plate and the mess-room door slid open.
                               2
                            The Host
       The departing crew were celebrating with a final dinner. Food-
packs and drinks flasks littered the crew-room table. As the door
opened, their captain stood up, three wine-filled beakers in his hands.
'There you are! Come on in and join the party.'
       Three space-suited figures stood motionless in the doorway,
their faces invisible behind dark helmet-visors. Uneasily, the captain
said. 'Come on, get your gear off and relax. You're going to be here
for another six...' His voice tailed off, as Safran raised his blaster.
'Hey, what kind of a joke is...' There was a sudden crackle of blaster-
fire and the captain's body was hurled backwards. As the other crew
members jumped to their feet, Meeker and Silvey shot them down.
When the noise and the cries died away, three dead bodies lay
sprawled across the room.
       'There will be one other,' said Safran. 'The station supervisor.
We must find and destroy him. Then we can make this the ideal place
in which to breed and multiply.' As he spoke, Safran was taking off
his helmet. A shining, metallic rash was spreading over his face,
thickening the eyebrows and altering the skin around the eyes.
       Meeker and Silvey showed no surprise. When they took off
their helmets, the same rash was on their faces too. The crew of the
Titan shuttle were no longer entirely human.

      The supervisor's office was the nerve centre of the base. It held
lockers, a wall map of the base, and master controls for the various
storage tanks.
      The station supervisor's name was Lowe, and he was a fussy,
methodical man. He sat in his office, nursing his injured pride.
Regulations were quite specific. On arrival at the refuelling base
incoming crews report to the station supervisor. Naturally enough,
most stopped off for a word with the crew they were replacing. But
he'd allowed plenty of time for that, and they really should he here by
now.
       Lowe touched the switch that would send his voice all over the
base. 'Shuttle relief crew, this is Supervisor Lowe. Please report to
me immediately.' There was no reply.
       Lowe flicked irritably at the controls of the visiphone on his
desk. Maybe they'd been delayed on the ship. He punched up a view
of the air-lock corridor on the little screen. Empty. They must be off
the ship by now. No doubt they were still drinking in the mess. Lowe
switched channels—and found himself looking at a room full of dead
bodies. He gave a gasp of horror. 'My God, what's happened?' With
trembling fingers he fumbled at the visiphone controls. A space-
suited figure appeared on the screen, walking down the corridor
towards him. 'What is it?' shouted Lowe. 'What's gone wrong?'
       The figure paused, then moved to the lens. Its face filled the
screen. 'Wrong? There is nothing wrong. This place is most suitable
for the Purpose.'
       Lowe peered at the screen. Surely that was Safran? But there
was something wrong with his face, and the voice... 'What purpose?
Safran, is that you? What's happened?'
       'Who is this—Safran?' asked the slurred, inhuman voice.
       Horrified, Lowe switched to the corridor outside his office.
Two figures were moving towards him. They had blasters in their
hands, and their faces showed the same inhuman distortions as
Safran.
       Lowe hurried to the door and locked it. He opened a panel in
his desk to reveal a high-powered space radio, and pressed a red
button marked 'Distress Call'. The transmitter started giving out a
high-pitched, urgent beep. 'Mayday, Mayday, Mayday,' said Lowe
urgently. 'This is Titan Base. Mayday, Mayday, Mayday.' He
switched the transmitter to record and repeat, crossed to a locker and
took out an emergency space suit. He pulled the locker away from the
wall, revealing a circular hatch. Quickly Lowe began climbing into
the suit.
       Silvey and Meeker reached the door to the supervisor's office
minutes later. They tried it, found it locked, turned their blasters on
the lock. There was a fierce crackle of energy and the locking device
melted away. They kicked the door open and burst into the room—
just in time to see the emergency escape hatch close. They ran to the
thick plastiglass window, but saw only the drifting clouds of gas and
the blackness of space beyond.
       Meeker turned as Safran came into the room. 'The supervisor
has escaped.'
       Safran considered. The part of his mind that was still human
knew that the emergency suits and escape hatches were intended for
use in case of some localised disaster, to enable station crew to reach
a rescue ship. The built-in back-pack carried only a very limited
oxygen supply. 'Leave him. Let him suffocate.'
       The bleeping of the distress signal was still filling the room,
Safran went to the set and switched it off. The bleeping died away
and he leaned over the transmitter. 'Titan Base, this is Titan Base to
all vessels. Disregard Mayday.'

       The TARDIS hung suspended in space, waiting for the Doctor
to decide on its new destination.
       A cloud appeared, and began drifting towards the TARDIS. As
it approached it seemed to grow bigger and more dense...

      Leela waited patiently while the Doctor made minute
adjustments to the TARDIS programme-circuits. Sensing her
boredom, the Doctor said, 'Shan't be long, Leela. As soon as I've
finished these checks we'll go somewhere really interesting.'
      Suddenly there was a high-pitched beep and a voice crackled
from the TARDIS console. 'Mayday, May-day, Mayday, this is Titan
Base... Mayday, Mayday, Mayday, this is Titan Base.' The same
message, repeated over and over.
      The Doctor flicked a switch, and the transmission was cut off.
He stood up, frowning at the console. 'What was that?' asked Leela
curiously.
      'Distress call from Titan. Took a while to reach us.'
      'Is Titan really interesting?'
       'What does that matter?' snapped the Doctor. 'What's important
is that someone needs help.' He began re-programming the TARDIS.
       Leela sighed. Sometimes it seemed she could never say the
right thing.

      The space cloud had drifted very close to the TARDIS by now.
It pulsed with energy and something gleamed and flickered in its
depths...

       Leela shivered.
       The Doctor stopped muttering incomprehensible calculations
to himself and looked up. 'What's the matter, Leela?'
       'I am troubled.'
       'What about?'
       'I don't know. I can—feel something.'
       'Don't worry,' said the Doctor vaguely, and went on with his
work.
       Urgent beeping filled the control room once again, and a voice
came from the console speaker. It was a different voice this time,
with something slurred and dragging about it. 'Titan—this is Titan
Base. All vessels, repeat, all vessels, disregard Mayday. I say again,
disregard Mayday. All under control. Our apologies, our apologies.
Titan Base out.'
       'That's it! ' said Leela suddenly.
       'That's what?'
       'That voice. It was something evil. It was not a human voice,
like the first one.'
       'It wasn't?' The Doctor stared at her in astonishment. He
opened his mouth to speak—then suddenly went rigid...

      As the TARDIS brushed the fringes of the drifting cloud,
something deep within flared into life, lashing out with a lightning-
tentacle of energy...
       The Doctor's body was surrounded by a kind of glowing halo.
The effect faded and the Doctor shook his head and went on with his
work.
       Leela was astonished and alarmed. 'What was all that about,
Doctor?'
       'Space static. Nothing important.'
       'But there was a kind of glow all round you...'
       'There was? Probably a kind of St Elmo's fire. It happens at
sea.'
       'St Elmo?'
       'Yes, it causes a sort of halo effect around the masts of ships.'
       'Halo?'
       'Why do you keep repeating everything I say?' asked the
Doctor irritably. 'You're not a parrot, are you?'
       'Parrot?'
       'Yes. A parrot's a bird that repeats things. Move over.'
       'Move over,' said Leela mischievously.
       The Doctor removed another panel and stared broodingly at the
inside of the console. It now seemed to be emitting a mysterious
crackling.
       'Is there something wrong?' asked Leela.
       'There isn't actually anything wrong,' said the Doctor hurriedly.
'Well, nothing serious, anyway. But I shall have to check all the
same.'
       Leela was staring at the maze of circuitry inside the console. 'I
can feel it, Doctor. Something is wrong...'
       The Doctor thrust his head inside the console. 'Now come on,
old thing,' he said reproachfully. 'Stop acting I up.' A lightning-like
tentacle of energy flashed from f the console and played about the
Doctor's forehead. He slumped forward unconscious, his head
crashing against the console. A deep throaty voice said, 'Contact has
been made.'

      Safran was showing his two crew-members the wall-map of
Titan Base. 'We shall start the incubation process—here.' He pointed.
'One of the largest fuel tanks is empty—it will become the Hive.'
     A gurgling inhuman voice spoke inside his mind. 'Contact has
been made. The Nucleus has found a suitable host. Prepare for his
coming...'

       With a wheezing, groaning sound the TARDIS arrived on
Titan, materialising in a corridor near the airlock.
       In the control room, Leela was desperately trying to revive the
Doctor. 'Wake up, Doctor, we've landed. We've materialised!'
       As she knelt by the Doctor, a fiery tentacle snaked from the
console and played about her head. Leela didn't even notice it. 'Come
on, Doctor. Wake up.'

      Safran, Silvey and Meeker came running down the corridor,
and waited outside the TARDIS. 'There is one other with the host,'
said Safran. 'She is a reject. We must destroy her, and dispose of her
body with the rest. Take up your positions.'
      All three moved back out of sight, blasters covering the
TARDIS door.

       The Doctor opened his eyes and said, 'Hello, Lalee.'
       'Doctor, are you all right?'
       'Rightly perfect, thank you, Lalee,' said the Doctor solemnly.
       'What did you say?'
       'I said I was perfectly all right, Lalee.'
       'My name is Leela.'
       'I know your name,' said the Doctor indignantly. 'Leela!'
       'What happened?'
       The Doctor sat up, rubbing his head. 'I must have had a bot of a
shick.'
       'What?'
       'A bot of a shick,' repeated the Doctor patiently. Suddenly his
body convulsed in a kind of spasm. Leela held his shoulders,
supporting him, and the attack passed as quickly as it had come.
       'What is it, Doctor?'
       'I'm not sure. A voice or something in my head...'
       'The evil thing!'
         'Nonsense, just a nasty turn.' The Doctor climbed rather
unsteadily to his feet. 'Come on, Leela, we're on Titan. Let's go and
take a look around.' He strode unsteadily towards the TARDIS door,
and rebounded from the edge. He paused, rubbing his shoulder. 'Odd,
that...'
         'Doctor, don't go out,' pleaded Leela.
         The Doctor grasped the edge of the door to steady himself.
'What? Why not?'
         Leela operated the control that closed the door.
         'It's out there, waiting. Something evil. Please, Doctor, don't
go!'
                            3
                      Death Sentence
     Waiting in ambush, Safran and the others saw the TARDIS
door open. They raised their blasters... No one came out, and the
TARDIS door closed again.
     They resumed their wait. Eyes fixed on the door, they failed to
see Supervisor Lowe peering through the corridor window. A few
minutes later, the watching face vanished as Lowe moved away.

       Out on the icy, windswept surface of Titan, Lowe groped his
way through the methane fog. He worked his way round the edge of
the base until he reached the emergency hatch through which he'd
first emerged. With painful slowness, he opened the hatch and
crawled back into the narrow tunnel.
       A few minutes later, he was back in his own office. As he'd
hoped, the office was empty. There only seemed to be three of his
attackers, and the strange blue box was engaging their full attention.
       Lowe went to his desk and took a hand-blaster from his
drawer. He peered cautiously out of his office, and hurried away
down the corridor.

      Inside the TARDIS, the Doctor and Leela were still arguing.
      But we must go out and investigate,' insisted the Doctor.
'We've had a Mayday call.'
      'No... I can feel something wrong.'
      'Intuition?'
      'I don't care what you call it, Doctor. I knew, I knew—even
before you were affected.'
      'What are you talking about, affected?'
      'Before you were knocked out...'
      'Leela, listen to me, I'm quite all right.' Gently but firmly the
Doctor moved Leela away from the console and reached for the door
control.
       Blaster in hand, Lowe arrived in the corridor behind the three
relief crewmen. 'Drop your weapons,' he ordered. 'I'm arresting you—
all of you.'
       It was a gallant attempt, but a very foolish one. Lowe was
dealing with three men who didn't much care whether they lived or
died, as long as they served the Purpose.
       Not one of them obeyed Lowe's call to surrender. All three
swung round. Silvey raised his blaster, and Lowe shot him down.
Safran and Meeker opened fire, but Lowe jumped back and both
missed. Before they could fire again, Lowe turned and fled down the
corridor. Safran and Meeker ran in pursuit...
       Hampered by his space-suit, Lowe pounded down the metal
corridors. He turned a corner and Meeker arrived in time to see the
door close behind him. Meeker reached for the door control but
Safran pulled him back. Anyone coming through the door would be
an easy target for Lowe's blaster—and it was their duty to stay alive
and carry out the Purpose.
       Instead of opening the door, Safran locked it. He pointed to a
wheel-valve beside the door. 'Turn off the oxygen supply.' Meeker
spun the wheel and there was an abruptly cut off hiss. Safran turned
away, satisfied. Lowe would suffocate or freeze.

       The TARDIS door opened for the second time and the Doctor
stepped out and looked around him. 'Nobody around. Not a soul.'
Leela followed him from the TARDIS, her knife in her hand. The
Doctor felt in his capacious pockets and found something that looked
like a whistle, put it to his lips and blew hard. Unfortunately it proved
to be some kind of duck lure—instead of a piercing blast, it produced
only a raucous squawk. The Doctor abandoned the whistle and called
loudly, 'Anyone home?'
       Leela saw a foot sticking out round a near-by corner. 'Doctor,
look! '
       They hurried over. The body of Silvey lay sprawled where it
had fallen. The Doctor stared down at it. 'Disregard Mayday,' he
muttered. 'That second call we heard. He said disregard Mayday.
Why?'
       Leela knelt and put a hand to the dead man's neck. 'He's still
warm.'
       'Don't be gruesome,' said the Doctor reprovingly.
       'I am a hunter...'
       'You're a savage!'
       'Perhaps—I am not ashamed of what I am. And I tell you I can
smell danger.'
       The Doctor looked thoughtfully at her. Although he often
teased her about it, he had a great respect for Leela's instinct. 'Evil
again, Leela?'
       She nodded. 'It is everywhere in this place.'
       'Then we'd better find it before it finds us. You stay here.'
       The Doctor set off down the corridor. 'I am no coward,' called
Leela indignantly. But the Doctor was gone. 'Stay here,' she muttered
rebelliously. 'He's always telling me to stay here! ' Mutinously she set
off in the opposite direction.

      Safran was studying the wall chart in the supervisor's office.
Meeker was standing ready by the controls.
      'Set temperature and humidity rate for optimum breeding
conditions,' ordered Safran.
      'Set temperature and humidity rate for optimum breeding
conditions,' repeated Meeker obediently.
      The Doctor appeared in the office doorway and watched them
for a moment. He cleared his throat loudly. 'Excuse me, you don't
know me. Allow me to introduce myself—'
      'There is no need,' said Safran placidly. 'We are preparing the
Hive now.'
      'People call me the Doctor—' The Doctor broke off. 'Hive?'
      'For the Nucleus which you carry within you.'
      The Doctor stared at him. There was a strange metallic rash
around the man's eyes, and the eyebrows were curiously thickened.
'Are you all right? I answered your Mayday...'
      'You answered the call,' corrected Safran calmly.
      'That's right. Has someone been hurt?'
      'It is of no consequence. The physical envelope is of no
importance.'
      'Of no importance,' chorused Meeker.
      'What do you mean, of no importance? I've just found a dead
body out there.'
      Safran came closer and stared at the Doctor. 'It is of no
importance—now that you have arrived.' A jagged, lightning-like
tentacle sizzled for a moment between Safran's forehead and the
Doctor's, and as suddenly vanished.
      'I have arrived,' said the Doctor in a slurred, dragging voice.
      'All that matters is that the reject should be destroyed.'
      'The reject must be destroyed.'
      'And breeding begin!'
      The Doctor nodded slowly. 'And breeding from my Nucleus
begin.'

       Leela crept silently along the corridor, senses alert, knife
poised and ready in her hand. She was passing a closed door when
she heard a faint scrabbling sound. She paused and listened. It was
coming from inside the door. It took her a minute to fathom the
workings of the locking mechanism, but she succeeded at last. The
door slid open and a stiff, frost-covered body fell out into her arms.
Leela lowered it to the ground, and knelt to check that the man was
still breathing. Deciding that he was alive—just—she dragged him
away.

       The Doctor took the blaster from Safran's hand. 'Leela is a
reject. She must be destroyed. She will not suspect me.'
       'One of us will follow,' said Safran calmly.
       'That isn't necessary...'
       Safran ignored him. 'The Nucleus within you must not be
harmed.'
       'Must not be harmed,' chanted Meeker.
       'Very well.'
     The Doctor moved off down the corridor, blaster in hand, and
Meeker followed.

       Leela hauled the ice-cold body along the corridor until she
reached an open door. Glancing inside she saw a room with chairs
around a central table, littered with the remains of food and drink.
The room also contained three dead bodies, but Leela didn't allow
this to distract her. She dragged the unconscious man inside, and
dropped him into a chair. The man seemed to be recovering
consciousness now, and he was shivering convulsively. Leela found a
plastic flask half-full of some kind of wine. She took it over to the
chair and forced a few drops of wine between the man's chattering
teeth. He gulped and spluttered. After a few moments he opened his
eyes and looked dazedly up at her. 'Who are you?'
       'We answered your Mayday. Who are you?'
       'I'm Lowe—Chief Supervisor.'
       'What happened here?' asked Leela.
       'They tried to kill me... the relief crew. They're insane. They've
already killed these poor devils.'
       'Why? Are they your enemies?'
       Lowe shook his head. 'No... they were my friends. I know
them—at least I thought I did. But they've changed.'
       'Changed?'
       'Their eyes, their manner, their whole behaviour is different.
One of them said something...'
       'What?'
       'About their purpose. "This place will be suitable for our
Purpose"... Whatever that is!'
       'The Doctor will understand. He will find us soon.' From
somewhere outside a voice called, 'Leela! Leela, where are you?'
       'That's him,' said Leela delightedly. 'That's the Doctor!
       She was about to call back when Lowe said, 'Wait, it could be a
trap. They may have some way of taking people over.'
       Leela couldn't imagine anyone controlling the Doc-tor, but it
was as well to be cautious. 'What do you want to do?'
       'Hide!'
      They crouched behind an overturned bench and waited.

        Blaster in hand, the Doctor moved along the corridor, Meeker
close behind him. 'Don't worry, Leela,' he called. 'It's only me. Listen
to me, Leela, there's nothing wrong with this place, it's most suitable.
It's a good place... a good place...'
        Leela looked worriedly at Lowe. It was the Doctor's voice all
right, but there was something wrong with the tone. All the warmth
and life seemed to have gone from it. And the words were strange...
        The Doctor walked along the corridor calling, 'Leela! Come on,
Leela, I'm waiting! ' He was quite calm. Leela was a reject and she
must die. It was necessary.
        Suddenly the Doctor stopped, looking at the blaster in his hand
as if he had never seen it before. His own personality came flooding
back and he gasped a desperate appeal to the power that had invaded
his mind. 'Please leave me... please! I can't do it... I can't...'
        Meeker came up behind him. 'Think of the Purpose. She is a
reject. She must die. Kill her!'
        'I can't...'
        'Think of the Purpose. The Purpose is all important!'
        Lowe shifted his position, caught an empty flask with his foot.
It rolled across the floor of the mess room. It was only the tiniest
sound but the Doctor heard it. His mental struggle suddenly ended as
the power in his mind grew stronger. He raised his blaster and
marched towards the mess room. 'The reject is here.'
        Meeker paused for a moment as if listening to some silent
command, then put a hand on the Doctor's shoulder. 'Stay—there is
danger. The Nucleus does not wish to be harmed. I shall destroy her.'
        'Kill her,' muttered the Doctor feverishly. 'Kill her!'
        Meeker sprang through the mess-room door, firing as he came.
        Lowe dodged and returned the fire. He missed, and the fringe
of Meeker's blaster-bolt numbed his arm. His weapon clattered to the
floor.
        Meeker raised his blaster to finish him off.
        Leela's knife flashed through the air and thudded into his chest.
He fell back, choking...
       In one smooth movement, Lecla sprang across the room,
plucked her knife from his chest, snatched the blaster from his hand
and moved into the corridor.
       Rubbing his arm, Lowe went over to the dying Meeker and
bent over him. 'Meeker! ' he whispered urgently. 'This Purpose...
what is it?'
       The dying man looked up—and smiled. A fiery tentacle.of
lightning flashed between his forehead and Lowe's...
       Leela saw a huddled shape lying face down at the end of the
corridor. It was the Doctor. She was hurrying towards it when she
heard a voice behind her. 'Leave it to me, I know this place.' Another
crewman was running along the corridor.
       Leela leaped behind the shelter of a projecting massive pipe
and waited in ambush.
       Behind her the Doctor rolled over and raised himself on one
elbow. He lifted his blaster, training it upon Leela's back. The hand
that held the weapon was covered with a thick grojvth of coarse
metallic hair.
       The Doctor's finger tightened on the trigger.
                              4
                          Foundation
        A deep, horribly gurgling voice spoke inside the Doctor's head.
'The reject must be destroyed. Kill the reject. Kill it.' Somehow the
Doctor found the strength to resist. 'I can't...' he gasped. 'I won't.'
        'You must!
        The Doctor's body convulsed, and he gave a strangled cry.
'Look out, Leela, I can't stop it.' In spite of his effort to resist, his
finger pulled the trigger. But the Doctor's internal struggle had
thrown off his aim. The blaster bolt passed harmlessly over Leela's
head, narrowly missing Safran who was edging his way along the
corridor. Safran jumped back, just as Lowe appeared in the mess-
room doorway. Outnumbered, Safran turned and fled, and Lowe ran
in pursuit.
        The Doctor writhed on the floor, at war with himself. With a
desperate effort he snatched the blaster from his own hand and threw
it away from him, writhing in agony. 'Got to fight it, got to fight it,'
he muttered feverishly.
        Leela knelt down beside him. 'Doctor, what's happening? What
was all that?'
        The Doctor's face was twisted with strain. 'I'm fighting for my
lives,' he whispered feebly. 'Whatever attacked the others is affecting
me.'
        'Then why doesn't it affect me?'
        'Perhaps because...'
        Another spasm shook the Doctor's body. 'I can feel it gathering
strength to attack again.'
        'The Evil One?'
        Almost inaudibly the Doctor whispered, 'Some kind of
organism that attacks the mind... the intelligence. It's trying to take
me over, Leela.'
        'No, Doctor, please...'
       'I need help... I must withdraw into myself. Save strength...'
"I'he Doctor's head fell back, and he lapsed into a self-induced trance.
Only by suspending all the functions of his body could he gain the
strength he needed to fight the intruder in his mind.
       Leela looked worriedly down at him. Again she murmured,
'But why not me?'

        Lowe caught up with Safran at the airlock door. He was
desperately swinging the locking wheel, and it was clear that he
intended to take refuge in the shuttle craft. At the sound of Lowe's
approach he swung round, blaster raised, but Lowe snapped, 'No!
Contact has been made. We are one, Safran.'
        Safran stared hard at him. There was a metallic rash around
Lowe's eyes, and his eyebrows were beginning to thicken.
        'Then why do you pursue me?'
        'For the Purpose... The Doctor still resists the power of the
Nucleus. You will stay here and prepare the tank for incubation. He
does not suspect me yet. I will stay with them, to guard the
Nucleus—and to destroy the reject.'
        They heard light, padding footsteps coming along the corridor.
'It is the reject,' said Lowe. He snatched a pair of space-goggles from
Safran's belt and thrust the crewman to the ground.
        When Leela came round the corner, Lowe was fitting the
goggles over his eyes. Safran's body sprawled at his feet. Leela
looked clown at it. 'You got him, then?'
        'Yes—but he almost got me. My eyes... I caught the flash from
his blaster.'
        'You must come with me,' ordered Leela. 'The Doctor is ill,
very ill. He told me to find help.'
        Lowe looked worried. 'There are only the most basic medical
facilities here...'
        'Where must we go then?'
        They began hurrying back along the corridor to the Doctor.
'Well,' said Lowe doubtfully, 'the nearest place would be the Centre
for Alien Biomorphology, the Bi-Al Foundation. It's in the asteroid
belt.'
      'We'll take the TARDIS,' said Leela decisively. She looked
down at the Doctor, who muttered and stirred. 'Doctor, we're taking
you somewhere to get help, but we'll need the TARDIS.' She turned
to Lowe. 'Where are we going?'
      'It's the Bi-Al Foundation, Asteroid K4067.'
      'What are the co-ordinates, Doctor?' She leaned over the
Doctor and shook him. 'Doctor, what are the co-ordinates?'
      The Doctor opened his eyes. 'Vector 1, 9, Quadrant 3.
      Lifting the Doctor between them, they began carrying him
towards the TARDIS. Leela muttered the co-ordinates to herself.
'Vector 1, 9, Quadrant 3.' Her knowledge of technical matters was
almost nil, but she had seen the Doctor take off in the TARDIS often
enough. Moreover, the Doctor had instructed her in basic takeoff and
landing procedures, saying she might need the information in some
emergency.
      Now that emergency had arrived. As she lifted the TARDIS
key from round the Doctor's neck, Leela hoped desperately that she
could remember what she'd been told. It looked as if the Doctor's life
depended on it.

       The Bi-Al Foundation was one of the largest and most
impressive research hospitals in the galaxy, occupying almost the
entire centre of the huge, hollowed-out asteroid. Set up by a number
of business conglomerates back on Earth, it was ideally placed to deal
with the frequent injuries and many strange ailments encountered by
the explorers who passed through the asteroid belt on their way to the
outer planets.
       The Foundation's thousands of gleaming windows shone
brilliantly out into the blackness of space, level upon level of them.
Embedded in the centre of the building was an enormous glowing red
cross, symbol of the healer since the earliest days of Man.
       They were used to strange craft and strange travellers at the Bi-
Al Foundation. Once the staff had recovered from the shock of the
TARDIS materialisation in main reception, they were treated like any
other space travellers. White-clad nurses lifted the Doctor on to a
trolley, and carried him to a lift, which whisked him out of sight with
a pneumatic whoosh.
       Leela and Lowe were left at the reception desk, where an icily
efficient lady sat in the midst of an array of communication devices.
Leela looked uneasily around her. Long white corridors radiated off
from this central area. There were bustling doctors and nurses in their
different coloured robes, huddled patients waiting on their benches.
Although she didn't know it, this was a basic hospital scene that
hadn't changed for thousands of years.
       The receiving officer was looking at her impatiently, fingers
poised over the computer terminal input keys. 'Patient's name?'
       'Er—he's just called the Doctor.'
       'Place of origin?'
       'Gallifrey.'
       'That's Earth, isn't it? Ireland?'
       'I expect so.'
       'Thank you, that's all we need for now.'
       'But where is he?'
       'Level X4, Isolation.'
       The receiving officer touched a control, and a monitor screen
showed the Doctor lying on a bed, surrounded by a complex array of
automated diagnostic instruments. 'He's being datalysed.'
       'Being what?' asked Leela, alarmed.
       'Treatment is already under way,' said the receptionist with
professional reassurance. 'Are you next of kin?'
       'Oh... yes. I don't know. I expect so.'
       Lowe came up to the reception desk. 'Where's the Doctor?'
       'They've taken him away,' said Leela helplessly. 'To level X4.'
       'X4?'
       'Isolation wing,' repeated the nurse briskly. She looked at
Lowe's goggled face. 'And what's your trouble?'
       'Blaster flash—it was an accident.'
       The receptionist pointed. 'Eye section, straight through, they'll
deal with you there.'
       Lowe nodded to Leela. 'I'll find you later, then.' He hurried
away.
      'Can I see the Doctor?' asked Leela hopefully. 'Not until
Professor Marius has examined him.'
      'Marius?'
      'He's our specialist in extra-terrestrial pathological
endomorphisms,' said the receptionist proudly. Then her manner
became formal again. 'Will you wait there please?'
      She pointed to a row of seats. Leela sat down to wait.

       The Doctor lay unconscious on a bed in the isolation ward.
Standing over him was Professor Marius, a stocky Germanic figure,
whose comfortable, informal clothes indicated that he was too senior
to be bothered with looking respectable. An explosively cheerful
professor from New Heidelberg University, Marius had come to the
asteroid belt in search of new and rare diseases. So far he had come
up with nothing sufficiently exotic to satisfy him.
       Hovering beside the bed were Parsons, Marius's keen young
assistant, and his senior nurse. Also included in the little group was
the squat metallic creature that stood near the bottom of the bed. It
looked curiously like a kind of squared-off metal dog, with a
computer display screen for eyes, and antennae for ears and tail. At
the moment it was studying the Doctor's motionless form with a very
sophisticated battery of scanning devices. A strip of computer-print-
out papers began sprouting from its mouth, rather like a very long
tongue.
       When the print-out strip stopped protruding itself, Marius
leaned down, patted the metal creature on the head, and tore off the
strip.
       He studied it for a moment and then looked up at his two
assistants. 'Blithering idiots! ' he said witheringly.
       Doctor Parsons and the Nurse exchanged glances and said
nothing. They were used to Professor Marius.
       'This man is in a self-induced coma,' continued Marius. 'There's
absolutely nothing wrong with the fellow. Look at him—he's
probably one of these good-for-nothing spaceniks!' Descendants of
the hippies and beatniks of the late twentieth century, spaceniks were
penniless wanderers who somehow managed to smuggle themselves
on board various kinds of space craft in their desire to commune with
the mysteries of the universe. Since they were without either financial
resources or technical skills, they usually landed in trouble, and had
to be ferried home by the Terrestrial Government at enormous
expense.
       Marius looked disgustedly at the untidy specimen before him.
'Why have I been sent for? Tell me that —why? It's a complete and
utter waste of my valuable time!'
       With a kind of electronic growl, K9 produced another data
strip. Parsons studied it. 'Excuse me, sir.'
       'What is it now?'
       'K9 indicates that this patient is not a member of the human
race.'
       Marius turned. 'Nonsense. Just look at him.'
       'See for yourself, sir,' insisted Parsons. He passed Marius the
data strip. 'Two hearts and a self-renewing cell structure.'
       Marius looked down. 'Is that right, K9?'
       The little creature spoke in a gruff metallic voice. 'Affirmative,
Master.'
       Marius examined the Doctor with a good deal more interest.
'Non-human, is he? Point of origin?'
       'Beyond the solar system.'
       With heavy sarcasm, Marius said, 'Thank you, K9.'
       'Master,' said the metal dog smugly. Irony was wasted on
automatons.
       Marius turned to the nurse, 'Let's get an encephalograph out on
him, eh?'
       The nurse reached for a complex piece of equipment on a
flexible arm, and swung it close to the Doctor's head.
       K9 transmitted the results. 'Unidentified viral-type infection
with noetic characteristics. At present seated in the mind-brain
interface, and therefore having no ascertainable mass or structure—
Master.'
       Marius rubbed his hands. 'Interesting! Most interesting! Not
every day we discover a brand-new infection, eh, Parsons?'
       'No, sir,' said Parsons dutifully.
       The Doctor opened his eyes. 'Hello! ' he said cheerfully.
       Marius was delighted. 'Good evening! '
       The Doctor looked at the maze of electronic equipment
surrounding his bed. 'Find anything?'
       'Not yet, my boy, but we will!' Marius looked at the chart at the
bottom of the Doctor's bed. 'You're a Doctor, I see.'
       'That's right. Come on now, what have you found?'
       'Cataleptic trance?' suggested Marius.
       'Yes.'
       'Self-induced?'
       'Yes.'
       'Why?'
       'Self-preservation,' said the Doctor simply. 'Whatever it is I'm
suffering from seems to thrive on mental activity.'
       Marius was fascinated. 'I see... so the harder you think, the
more of a grip it seems to take?'
       'That's right. Non-thinking is the only way to shake it off—but
I can't stay mindless for eternity, can I?'
       'Take your point. take your point,' mumbled Marius
sympathetically. 'Now. my computer here...'
       The Doctor looked down and seemed quite unsurprised to see a
robot dog at the end of his bed. 'Hello, old chap, good dog! '
       'Hullo!' said K9 politely.
       'And how are you?'
       Before K9 could reply, Marius cut firmly through these social
exchanges. 'As I was saying, Doctor, K9 seems to think that the virus
is noetic in character—which means it would only be detectable
during consciousness.'
       'I know what noetic means,' said the Doctor irritably.
       'I'm sorry.'
       The Doctor waved the apology aside. 'So, the virus is
somewhere in the mind-brain interface?'
       Marius shrugged. 'If it exists...'
       The Doctor was caught up in his own deductions. 'Of course,
how stupid. That's why it attacked the TARDIS computer first,
because it was showing the greatest amount of mental activity. I was
just idling, so to speak...'
       'When was this?'
       'When we were first attacked, on our way to Titan. I assumed it
was just a static build-up. And then when I checked the computer it
jumped into my mind—and that explains why Leela was unaffected.
Have you met Leela? She's all instinct and intuition. That's why the
virus rejected her. Of course, I can see it all now!'
       'It's possible, possible,' said Marius, who didn't really see at all.
A thought struck him. 'Was anyone else exposed to this virus of
yours?'
       'Yes, the entire crew on Titan succumbed to it—with one
exception, a man called Lowe. He came here with us...'
       'Supervisor Lowe is in the eye section,' volunteered K9. He
was linked to the main hospital computer and knew most of what
went on.
       'Are you sure?' snapped Marius.
       'Affirmative.' As always when his answers were questioned,
there was a slightly huffy note in K9's voice.
       Marius turned to the Doctor. 'Are you sure that this man Lowe
was exposed—'
       He broke off. The Doctor was lying back motionless, eyes
closed. Feeling the alien force in his mind gathering strength,
struggling to lash out and take over Marius and the others, the Doctor
had returned to his trance, determined to starve it of the mental
energy upon which it fed.
       'Oh, he's gone again,' said Marius disappointedly. 'I want him
kept under constant observation. Full monitoring. See to it, K9.'
       'Affirmative, Master.'
       Marius turned to his assistant. 'We'd better get hold of this chap
Lowe and take a look at him. Even if he wasn't affected, he could still
be a carrier...'

      Supervisor Lowe was sitting in an examination chair with an
eye specialist standing over him. 'How did this happen?'
      'An accident—on Titan.'
      'What sort of accident?'
      Lowe didn't reply. The specialist sighed. 'Well, let's have a
look at you...'
      'Certainly,' said Lowe. He lifted the goggles from his eyes, and
a sudden lightning-streak flashed between his forehead and that of the
doctor.
      The specialist staggered back, hand to his eyes. When he
lowered the hand a second later, his face was quite calm.
      In a slurred, dragging voice he said, 'Contact has been made.'
                             5
                       Counter-attack
       It didn't take Leela very long to get bored, sitting in the
reception area waiting for news. She'd never been one to pay much
attention to the orders of authority. Choosing a moment when the
receptionist was busy, Leela slipped out of her seat, and went to look
for the Doctor.
       She'd memorised the only clue she had to his whereabouts—
level X4—and there were plenty of signs to follow. There were
plenty of people moving along the white corridors, specialists
striding in solitary majesty, chattering groups of medical students,
nurses murmuring quietly together. One or two people glanced
curiously at her, but the Bi-Al Foundation was used to strange
visitors. No one made any attempt to stop her, or ask her where she
was going.
       Distrusting the high-speed lift, Lcela reached level X4 by
climbing endless flights of service stairs. When she reached level X4
at last, she found herself in another complex of white corridors,
though these were silent and empty.
       She saw a door ahead of her marked 'Isolation Wing. Strictly
No Admittance', and promptly opened it.
       Behind it she found the Doctor, stretched out on a kind of
couch, surrounded by an array of instruments. 'Doctor!' said Leela
delightedly.
       To her astonishment, a kind of robot animal glided from the
other side of the couch and began barking orders at her. 'Negative,
negative, negative, no entry!'
       Leela had no intention of being chased away now she'd found
the Doctor at last. Her hand went to the blaster thrust into her belt.
'Look, you—whatever-you-are...'
       'I am K9,' interrupted the little creature importantly, 'and I am
warning you...'
       Leela drew her blaster. 'Look, I came to see the Doctor—I
arrived with him.'
       K9 ignored the explanation, his attention focused on Leela's
blaster. 'I too have offensive capability,' he said proudly. A stubby
blaster-muzzle protruded from just under his nose. 'You have been
warned. Retreat, retreat!' K9 glided menacingly towards Leela.
'Patient in total isolation. Contagion risk. Retreat, retreat!'
       Leela backed away—and bumped straight into the stocky
figure of Professor Marius, who was just coming through the door
behind her. 'Who are you?'
       'I am Leela.'
       'Ah, yes, of course. The Doctor's aide?'
       'I think so.'
       Marius looked down at his bristling companion. 'K9,
memorise. Friend.'
       The muzzle of K9's blaster retracted. 'Memorised. Friend.'
       'Is that tin thing something to do with you?' demanded Leela.
       Marius was indignant. 'That tin thing is my best friend and
constant companion. He's a computer!' Leela looked bemused and
Marius explained. 'You see, on Earth I always used to have a dog.
But up here, with the weight penalty, well, it's just not possible. So I
had K9 made up. He's very useful, my own personal data bank.
Knows everything I know, don't you, K9?'
       'Affirmative—and more—Master!'
       Ignoring this hit of robotic conceit, Marius went over to his
patient. 'I'm afraid there's not much I can tell you about the Doctor
yet.' He looked appraisingly at Leela. 'You know, I should like to
have you scanned and datalysed.' Leela backed away in some alarm.
'Just to see why you're immune. You see, if we can isolate that factor,
we can inoculate against it. Do you understand me?'
       'I'm sorry,' said Leela blankly.
       Marius looked thoughtfully at her. 'Yes. perhaps the Doctor
was right. Maybe it is all a matter of intelligence...'
       Parsons came hurrying into the room, and Marius said sharply,
'Well, what about this Lowe chap? Where is he?'
      'He was in the eye section, sir, but he's disappeared. The
consultant seems to have vanished as well...'

       A trolley was being wheeled slowly along the hospital
corridors. Lowe lay stretched out on it, and the trolley was being
pushed by the eye consultant who had attempted to treat him.
       Two young doctors appeared, walking towards them. 'Who are
they?' hissed Lowe.
       'Doctors. Cruickshank and Hedges.'
       'Get them over here.'
       The consultant raised his voice. 'Cruickshank, Hedges,
interesting eye-case here. Come and have a look!'
       Unsuspectingly, the two young doctors wandered over.
Cruickshank bent over to look at the patient. Hedges suddenly
became aware that the consultant was staring at him with strange
intensity. 'What is it?'
       'Now!' hissed Lowe.
       A jagged lightning-streak flashed between the foreheads of
Lowe and Cruickshank, Hedges and the consultant. Slowly the two
doctors straightened up. 'Contact has been made,' said Cruickshank,
in a slurred dragging voice.
       In exactly the same tone, Hedges said, 'Contact has been made.'
       Lowe sat up, and swung his legs down from the trolley. 'A
place has been found, most suitable for our purpose. Titan is being
prepared as a Hive. Meanwhile our duty here is twofold. To guard the
Nucleus, which is in the mind of one called Doctor, and to make
contact with the best minds here. When we leave for incubation on
Titan, all rejects will be destroyed.'
       The consultant studied the two new servants of the Purpose.
'Do you understand?'
       'We understand,' said Cruikshank.
       'Contact must be made,' said Hedges.
       Reverently Lowe whispered, 'For the Purpose!'

     Leela lay apprehensively on a couch, being scanned by a
complex of instruments similar to that surrounding the Doctor.
Marius, Parsons, and a nurse stood over her. K9 waited at the foot of
the bed, ready to convey the results of the scan.
      'Virus contamination would seem to be complete and total,'
Marius was saying in his best lecturer's voice. 'If there is anything
unique in her metabolism that enables her to resist, the scanner will
detect it.'
      Lights flashed, instruments buzzed, clicked and whirred. At
last K9 said, 'Negative on immunity, Master.'
      'But there must be something!'
      Parsons looked doubtful. 'But what if there isn't, sir?'
      Marius looked over at the couch that held the Doctor. 'Then
he's our only guinea-pig, the only one to be affected by the disease
and yet be able to resist it.' Marius came to a decision. 'I can't allow
him to be taken over like those poor devils on Titan. If there's no
immunity factor in Leela—I will have to operate on the Doctor!'

      Lowe and his three new recruits were walking steadily along
the corridors, when suddenly Lowe stopped dead. He went rigid, a
hand to his forehead. 'Contact!'
      A throaty, gurgling voice spoke inside Lowe's head. 'I am
endangered...'
      Reverently Lowe said, 'It is the Nucleus...'
      'The host is threatened...' said the gurgling, in-human voice.
      Lowe listened for a moment longer then turned to the others.
'The Nucleus says that the Doctor, its host, is in danger. We must act
before it is too late. Now, all of you—concentrate.'

     The captain of the Bi-Al supply shuttle sat relaxed in his
command chair, his two crew members dozing in their acceleration
couches behind him. They would soon be approaching Asteroid
K4067, and the computer would carry out the simple docking
manoeuvre with its usual efficiency... Everything was routine...

      Outside, in the blackness of space, a drifting, formless cloud
had appeared from nowhere, materialising directly in the path of the
shuttle. As the shuttle passed through it, lightning streaked from the
cloud and played about the ship...

      Suddenly the shuttle captain noticed that the ship was
increasing speed. It was boosting to maximum power-drive—and
heading straight for the asteroid.
      Panic-stricken, he tried to switch the controls to manual.
Lightning tentacles flashed from the computer keyboard and played
over his head and those of the two dozing crewmen. The shuttle
captain sat back in his chair, watching calmly as his ship hurtled
towards certain disaster. Contact had been made—for the Purpose.
Everything was in order...

       It took some time to prepare the Doctor for his brain operation.
Marius insisted on taking scan after scan of the Doctor's brain, and he
made all his preparations with agonising care. He knew that the
operation was a last desperate hope, and that there was a chance the
Doctor would not survive it.
       Marius accepted the responsibility unflinchingly, for he knew
the alternatives. Either the Doctor would become the slave of the
alien force in his mind, or he would remain, in his own words,
mindless for all eternity.
       The Doctor was ready at last. Robed and masked, Marius and
Parsons leaned over him as he lay on the operating table. K9 waited
to monitor the operation. Leela hovered uneasily by the door, not
wanting to stay, yet unwilling to leave the Doctor.
       In a calm, steady voice, Marius was giving his final
instructions. 'No anaesthetics yet, Parsons, he's still in the self-
induced trance. K9, monitor the brain. If he shows signs of emerging
from the coma, warn me at once, otherwise the shock might kill him.'
       'Affirmative, Master.'
       Marius leaned forward, ready to make the first delicate
insertion of the laser micro-probe into the Doctor's brain. A voice
blared from the speaker. 'Emergency, emergency! All stations, all
stations, emergency. Supply shuttle approaching base on collision
course, apparently out of control, refusing to respond to signals. All
medical personnel report to casualty at once. Repeat, all medical
personnel.'
       Marius lowered the scalpel with a groan of protest. 'Now? Why
now?'
       For a moment he considered continuing with the operation,
then abandoned the idea. He could scarcely carry out a delicate brain-
operation with the entire base in chaos. Besides, it was impossible to
predict what damage the collision might cause. An interruption in
power supplies for instance would be literally fatal.
       'Repeat, emergency, emergency!' said the speaker voice. 'All
medical personnel to casualty immediately.'
       'We'll have to go, sir,' said Parsons despairingly.
       'Yes, yes, I know we have to go. K9, stay in charge here. No
one is to come into contact with him. Have you got that? No one!'
       'Affirmative! '
       'Well, come along, Parsons,' roared Marius, and rushed from
the room, Parsons trailing behind him. Leela stood looking anxiously
down at the Doctor.
       His face was calm and still. There was no sign that he was still
alive.

      The supply shuttle screamed out of space and crashed into the
side of the Bi-Al building. Debris shot up-wards and floated away.
Masonry, equipment and people too were sucked into space as the
damaged sections depressurised.
      The shuttle embedded itself deep into the side of the
building—but not at random. The point of impact had been precisely
calculated...

       There was a shattering thud, cries, screams, the shriek of
tortured metal and plastic. The whole room shook, lights flickered
and then came on again. Leela staggered, fighting to keep her
balance. The shock of the impact woke the Doctor up. He opened his
eyes and said peevishly, 'What's that?'
       Leela got to her feet. 'There's been some kind of accident—a
shuttle crashed. They've all gone to help.'
       'Where did it hit?'
       It was K9 who answered. 'On level X3 below. As a result of
structural damage this area is now cut off.' The Doctor sat up. 'What?'
he shouted.

      Lowe and his three helpers ran along a corridor, and found
their way completely blocked by fallen rubble. Lowe turned to the
consultant. 'We have to get to level X4. There must be other ways.'
      'We could try the service shaft—but it would take longer.'
      'Then hurry!' snarled Lowe.
      The consultant led them away.

       The voice from the speaker said, 'All available personnel to
accident zone on level X3, repeat, level X3.'
       The Doctor seemed to have recovered, at least for the moment.
'I don't think that was an accident.'
       'Why not?' asked Leela.
       'It must be something to do with whatever's in my head,' said
the Doctor positively. 'K9, could I have a word with you?'
       'Affirmative.'
       Leela began edging towards the door; and the Doctor said,
'Where are you off to?'
       'I think I'm needed out here.'
       Leela slipped out of the room and stationed herself just outside
the isolation ward door, drawing her blaster. She didn't completely
understand what was going on—but she had a well-developed
instinct for approaching danger. If the accident had been planned to
isolate them, as the Doctor seemed to think, it could mean only one
thing—their enemies were about to attack. Pleased to be faced with a
problem she could understand and deal with, Leela drew her blaster
and waited...
       Inside the isolation ward the Doctor was saying impatiently,
'Cloning techniques, K9! Give me a rundown, state of the art so far...'
       K9 liked nothing better than to be asked for some of his ample
store of scientific information. He gave a sudden beep, the robotic
equivalent of clearing his throat. 'Cloning is a form of replication,
making a copy of an individual using a single cell of that individual
as a matrix. Clones retain characteristics of original organism.'
       'Go on, go on! ' said the Doctor urgently.
       'Successful experiments first carried out in the year thirty-nine,
twenty-two.'
       'Thirty-nine, twenty-two. Good, good! Carry on.' K9 continued
his lecture. 'More recently, the development of the Kilbracken
technique of rapid holograph-cloning...'
       The Doctor listened, his mind racing. He was beginning to
form a plan... a plan that would enable him to fight back at the
strange force that threatened to take him over. He had very little
time...
                             6
                         The Clones
       The end of the corridor was totally blocked by a twisted mass
of metal—the remains of the shuttle-craft that had embedded itself
into the foundation. Surrounded by members of his rescue squad, the
faithful Parsons at his side, Marius was examining two shattered
bodies that had been recovered from the wreckage, Both had
curiously thickened eyebrows and a metallic rash about the eyes.
       Marius straightened up, his face grave. 'If these two
unfortunates have contracted the virus, we must assume that they all
have. If we attempt further rescue and treatment, the disease could
spread like wildfire and wipe out the entire Foundation.' He waved
the rescue squad away. 'Everybody back. Clear the area. Everybody
out of here! ' He turned to the head of the squad. 'I want the whole
area cryogenically cocooned until we find out more about the nature
of this virus. Get out the helium pumps. Parsons, nurse, come with
me, we must attend to the Doctor!'

       Other people had plans for the Doctor, too. Lowe and his three
aides were creeping towards the door of the isolation ward. They had
broken into a security-locker, and now all four were armed with
blasters.
       Lowe was in the lead. He edged round a corner—and found
himself facing Leela, blaster in hand. Mutually astonished, both fired
at the same time. Both missed.
       'Destroy her,' screamed Lowe. 'That's the reject.'
       'Reject yourself,' shouted Leela, and sent another blaster-bolt
sizzling towards his head. Lowe ducked back just in time. He and the
others found cover and began shooting back. Soon blaster-bolts were
sizzling up and down the corridor.
       In the middle of it all Marius and Parsons came running along
the corridor from the other direction, followed by Marius's nurse.
Leela yelled over her shoulder, 'It's Lowe—he's got the disease! Get
inside, I'll cover you.'
       The three leaped inside the isolation ward where K9 was just
concluding his lecture. 'At present, holographic-cloning technique is
simple but unreliable.'
       'Hurry, K9, hurry!'
       Rapidly speeding up his delivery K9 gabbled, 'Holographic
replicas do not maintain their existence because of possible unsolved
psychic problems.'
       'How long, how long?' demanded the Doctor.
       'Longest recorded life, ten minutes.'
       'Ten minutes fifty-five seconds,' corrected Marius. The Doctor
looked up eagerly. 'Professor Marius, could you clone me?'
       Marius shrugged. 'Certainly. The Kilbracken technique is
almost absurdly simple. But it's a circus trick, no medical value.'
       'Could you clone me now?'
       'Now?'
       'Yes. Because if you don't clone me now, and the virus gets to
me, it'll take the whole Centre over.'
       Leela fired off a final volley of blaster-bolts. The last one
fizzled out in a dispirited whine. She ducked back inside the ward.
'Can't hold them off any longer, out of ammunition.'
       'K9!' snapped Marius. 'Kalaylee!'
       'Affirmative, Master!'
       'What does that mean?'
       Marius smiled grimly. 'He knows!
       Blaster-muzzle projecting, K9 trundled out into the corridor
like a small canine tank. He blazed away at the attackers, who were
rushing forwards, confident of victory. His first shot blasted down the
astonished Hedges. Lowe and the others turned and fled. When they
were safe round the corner, Lowe paused. 'We'll never get past them
that way. Is there a visiphone?'
       'In my office,' said the consultant. They hurried away.
       Marius and his nurse were supervising the installation of a
portable booth with opaque plastic sides, not un-like a twentieth-
century telephone kiosk. A tiny control panel was set into one side.
'Hurry, Marius, hurry! ' urged the Doctor. His brief spell of recovery
seemed to be coming to an end, and he was weakening rapidly. Deep
in his mind, the dormant virus was struggling to reassert its control.
       Marius checked circuit-connections, and waved the technicians
away. He went over to the Doctor, lifted a scalpel from an
instrument-tray held by his nurse and took a minute sample of the
Doctor's skin.
       'You must realise, Doctor, that this will not be, in any real
sense a clone but a short-lived carbon-based imprint, a sort of living,
three-dimensional photograph.'
       The Doctor's strength was fading rapidly. 'Leela,' he muttered.
'I shall need Leela...' He fell back, unconscious.
       Leela checked the blaster she'd taken from Hedges's body.
'What did he mean, he needs me?'
       'It must be because you are immune. I think he wants you
cloned as well.'
       Marius picked up his scalpel and reached for Leela's hand.
       'But what will happen to me, the real me?'
       'Nothing. Nothing at all,' said Marius soothingly. 'But you said
it was just short-lived.'
       Marius transferred his skin sample into the special cloning dish
and added the necessary nutrient solutions, talking as he worked. 'A
permanent clone or copy is theoretically possible, but it would take
years to achieve because of the experiential gap.' He carried the
containers over to the booth. 'Now in this way we manage to transfer
both heredity and experience, but the transfer is unstable...'
       'What does that mean?'
       Marius sighed. 'It means that your photo-copy twin will
deteriorate and vanish after a maximum life of ten or eleven minutes.'
       Leela felt it would be rather unpleasant, watching yourself fade
away and disappear. 'Oh, I see,' she said politely. 'Then in that case I
don't think I'll stay to see her. If you need me I shall be with K9.'
       'Yes, yes, yes,' said Marius impatiently, and carried the first
cloning dish over to the booth. He nodded to Parsons, who switched
on the machine. There was a hum of power and a steadily rising beep.
The booth was flooded with dazzling light, and inside the radiance a
shape began to form
       It cohered, solidified, and seconds late the Doctor stepped out
of the booth. The second self was identical to the Doctor on the
couch—the Kilbracken technique had reproduced every detail,
including clothing. The new Doctor nodded briefly to Marius and
headed for the door.
       'Doctor, where are you going?'
       The new Doctor turned. 'Trust me, Professor Marius, just trust
me.' He disappeared through the door.
       Marius sighed. 'I hope he knows what he's doing. Come along,
Parsons, we'd better get on with cloning the girl.' He picked up the
second cloning dish and carried it over to the booth.
       Leela, the real Leela, looked up in astonishment when the
Doctor, apparently restored to full health, Caine out of the ward and
strode briskly down the corridor.
       Staring after his disappearing figure she asked, 'Which one was
that?'
       K9's sensors enabled him to differentiate between original and
carbon copy. 'That was the Doctor-2.'
       'Can you explain?'
       'Affirmative.'
       'Well?'
       'The Kilbracken holograph-cloning technique replicates from a
single cell a short-lived carbon copy. Efficacy of individuation not
completely guaranteed.'
       'Can you explain simply?'
       'Negative! ' said K9.

      The consultant led Lowe and Cruickshank into the eye
section—and straight into one of the consultant's students, who
looked curiously at them. 'Come here,' snapped the consultant. The
student came over to them. Lightning sizzled between the
consultant's forehead and his own...
       The cloned version of Leela stood fully formed inside the
booth. Marius was about to release her when he heard a horrified cry
from his nurse. 'Professor Marius —look at the Doctor!'
       Marius turned. While they had been busy, the virus had taken
over the Doctor's body with horrifying speed. The entire shape
seemed twisted and distorted, and a rash of wiry metallic hairs had
grown over his hands and face. It was as though the Doctor were
turning into some strange deformed beast before their eyes. His entire
body was twisting, writhing, convulsing with such force that Marius
feared he would break a limb. He fetched heavy plastic restraining
webbing from a locker, and he and Parsons fought to strap the
struggling figure down.
       As they fought with him the Doctor began to speak, not in his
own voice, but in deep, throaty, gurgling inhuman tones, that
sounded like someone choking on his own blood. 'Release this body,'
gurgled the voice. 'You cannot prevail. I am the One. It is my
Purpose. It is my destiny. Let me go, you fools!'
       'Shall we sedate him?' asked Parsons.
       Marius fastened the last buckle with a mighty effort. 'No. Not
yet.'
       'What about the danger of contagion?'
       'No, Parsons. If the disease was contagious during this stage,
we would all have got it by now.'
       Parsons looked down at the writhing figure. 'If the Doctor's
right, sir, and the virus is intelligent, it must have some reason for
choosing him.'
       'That's right. In my view, we could be dealing with some kind
of leader.'
       The horrifying voice came from the Doctor's twisted mouth
once more. 'My Purpose. You must not delay my Purpose. The place
of the Hive is ready. Release me!'

        The TARDIS doors opened and the carbon-copy Doctor
emerged carrying a complex piece of electronic equipment. Clasping
it to his chest, he hurried off down the corridor.
       The visiphone screen in the isolation ward suddenly lit up and
Lowe appeared on the screen. The rash had spread all over his face
now, and like the Doctor he seemed scarcely human. 'Professor
Marius, listen to me,' he said menacingly. 'You must release the
Doctor.'
       Marius struggled to hold down the writhing figure on the
couch. 'Never,' he gasped defiantly.
       'I warn you, we are in control of the entire Centre. We have
made contact with your atomic generator technicians. If you do not
do as I say, I shall destroy your Foundation!'

       Waiting in the corridor with K9, Leela saw the Doctor hurrying
towards them clutching a heavy piece of equipment, which she
recognised as part of the TARDIS console. He marched straight past
them and into the isolation ward.
       'That was the Doctor-2,' said Leela definitely.
       'Affirmative!'
       As the second Doctor came into the ward, Lowe was still
uttering threats from the visiphone screen. 'You have two minutes in
which to decide. Either you give us the Doctor or your Foundation
will be wiped out!' The screen went dark.
       The Doctor was carrying his piece of equipment over to the
cloning booth.
       Marius followed him. 'What are you doing, Doctor? Didn't you
hear? We've just had an ultimatum.'
       'Don't worry, Professor, if this doesn't work the whole place
will be wiped out anyway.'
       Marius stared at the machinery. 'What is it?'
       'It's a Relative Dimensional Stabiliser, RDS.' 'What does it do?'
       'It's part of the TARDIS control system, the part that allows me
to cross the dimensional barriers.'
       Marius looked blank. The Doctor said, 'It's quite simple, really.
It means that I can change size, large or small as I wish.' He opened
the door to the booth, and found himself facing an angry carbon-copy
Leela. 'Why have I been left here?'
       'Sorry, Leela, shan't keep you a minute.' The new Doctor began
setting up the RDS inside the booth. 'Now listen carefully, Professor.
I'll operate the RDS. I've set it so that we'll be reduced to micro-
dimensions. You then scoop us both up and inject us into my master-
print, there.' He nodded briefly at the figure on the couch. 'When we
return, you simply throw the RDS in reverse to restore us to normal
size. This lever here... Any questions?'
       Marius had only one. 'Why take Leela?'
       'Because she's immune—and because she's a hunter!
       'Yes, of course. Well, we'd better get on with it, there's not
much time. Is there anything we can do meanwhile?'
       'Yes, just stay here and hope we come up with the antidote.
And Professor, when we emerge, we'll be corning out through the
tear duct!'
       'Right. Good luck! '
       The carbon-copy Doctor stepped inside the booth with the
carbon-copy Leela.
       Meanwhile the original Leela, overcome by curiosity, was
watching from the doorway. She caught a glimpse of her carbon copy
through the open door of the booth. 'K9, do I really look like that?'
       'Aflrmative.'
       There was a hum of power from inside the booth and the dim
shapes of the Doctor and Leela dwindled rapidly to nothingness.
       Marius waited a moment longer, then opened the door. The
booth was empty except for the little dish of serum in the centre of
the floor. Marius picked it up carefully, and his nurse handed him a
specially prepared pneumatic syringe. Marius sucked up the few
drops of colourless fluid in the dish and carried the syringe over to
the couch. He looked at Parsons. 'Well, here they go!' He bent over
the couch. 'Pleasant journey, Doctor,' he whispered, and injected the
fluid into the back of the Doctor's neck.
       Lowe's face appeared on the visiphone screen. 'Your time is
up,' he said harshly. 'Surrender the Doctor!'

     Carbon-copied and miniaturised, the Doctor and Leela found
themselves spinning round and round in a rushing crimson whirlpool,
as the Doctor's blood-stream carried them along the spinal cord,
towards the menace that lurked in his brain...
                              7
                          Mind Hunt
       Like swimmers carried to the bank of a rushing river, the
crimson tide deposited the cloned Doctor and Leela on to a solid,
lumpy, blue and pink surface, in a gloomy, echoing tunnel. The
Doctor helped Leela to her feet. 'We must be somewhere near the top
of the spinal column...' He looked round interestedly. 'Well, what do
you think?'
       Leela wasn't quite sure what to say. 'I don't know what to think,
I've never been inside anybody's head before.' Politely she added, 'It's
very interesting.'
       'Thank you,' said the Doctor, with equal politeness.
       'Why aren't we wet?'
       'Because we're too small to break the surface tension...'
       A kind of abbreviated lightning-flash crackled over their heads
and zipped away into the distance. 'What was that?'
       'Oh, just a passing thought,' said the Doctor airily.
'Electrochemical reaction in the synapses. Leg wants to move,
probably...'

       The leg of the tied-down Doctor flailed violently, kicking
against the restraining straps. Marius looked worried. 'Don't think he
can hold out much longer, the virus seems to be strengthening its
grip.'
       From the visiphone screen Lowe said angrily, 'Professor
Marius! You have not replied to my ultimatum. I can destroy this
Centre!'
       Marius swung round, holding up his hand. 'No, wait! I agree to
your terms. I have no further use for the Doctor, he's yours whenever
you want.'
       'A wise decision,' said Lowe coldly. 'Tell me, Professor, is the
reject Leela with you?'
        'No, as you can see, there's simply myself and my assistants.
She's somewhere in the Foundation, I've no idea where.'
        'No matter. She will be found and destroyed. Stay where you
are—we are on our way.' The visiphone went blank.
        Marius moved to the doorway and called softly, 'Leela?'
        Leela hurried into the room, K9 at her heels.
        'They're coming, Leela,' whispered Marius urgently. 'We've got
to hold them off for at least ten minutes. Can you do that?'
        'Can I borrow K9?'
        'Yes, certainly. K9, co-operate with Leela.'
        'Master.'
        Leela looked down at her ally. 'We'll have to wait for them in
the corridor. If we could just make some sort of barrier...'
        'Re-check! ' said K9 firmly. 'First we must eliminate the service
shaft.'
        Leela was pleased to see K9 had good strategic sense. 'Yes, of
course, otherwise they can attack us from behind... What we'll do—'
        Marius broke in on their planning session. 'Whatever you're
going to do, I should get on with it. We haven't got much time.'
        Leela took command. 'K9, you go and destroy the shaft, and
then meet me back here.'
        'Affirmative.'
        They moved off, K9 in one direction, Leela in the other.
        'Suppose they fail?' asked Parsons gloomily. He was beginning
to feel that their success depended on increasingly strange allies. First
two cloned miniatures, now a savage and a robot dog.
        Marius crossed to a security locker, opened it and took out two
hand-blasters. 'Ever used one of these?'
        He pressed one of the weapons into his assistant's hand. 'Here,
take it. If by any chance I am taken over by the virus, I hope you
won't hesitate to use that blaster on me. Because if you are taken
over, I shall certainly use mine on you. Whatever happens, we must
give the Doctor his ten minutes.'
        'I understand, sir,' said Parsons loyally, hiding the blaster
beneath his gown.
       The cloned Doctor and Leela were trudging through a sort of
soft swampy grotto, festooned with hanging veils of tissue and fine,
fungoid webs. Everything was enveloped in murky gloom, though
from time to time a bright, lightning-like thought-flash zipped by
over-head.
       'Doctor,' said Leela reproachfully, 'I do not think you have any
idea where we're going.'
       'What do you mean, no idea? We're travelling along my neural
pathways, looking for a sort of bridge, a crossover point between left
and right lobe.'
       'Is that where the virus will be?'
       'Wells since it seems to be able to control both conscious and
unconscious functions, it's a good place to start looking.'
       'Suppose we meet it?'
       'I don't think we will, not just yet. It came through the optic
nerve. We're still somewhere between the spinal cord and the
cerebellum. But keep your eyes open for tissue degeneration.'
       'Like this?' Leela jabbed her foot at a darker patch of the tissue
that surrounded them.
       The Doctor winced. 'Steady, that's me you're kicking!'
       'Sorry,' said Leela penitently. They hurried on.
       Behind them, white formless shapes were gathering, trailing
them through the neural pathways. The Doctor's body was preparing
to deal with the alien intruders...

      K9 glided back to Leela. 'Mission accomplished,' he announced
proudly. 'Service shaft destroyed—Mistress.'
      'Thank you, K9. Now what we need is some sort of barrier.'
      K9's blaster-nozzle protruded and he blasted the opposite wall
and ceiling with maximum force. Immediately most of the ceiling
crashed down. K9 fired again, and a chunk of wall landed on top of
it, making a wall of rubble across the corridor.
      'Acceptable?' enquired K9.
      'Perfect! Thank you, K9.'
      'There is no need for gratitude. I am an automaton.'
      Leela was scanning the corridor ahead. 'Really?'
      'I am without emotional circuits. Only memory and awareness.'
All the same, K9's tail antenna was wagging gently. He, too, was
scanning the corridor and his sensors picked up the sound of the
enemies' approach before they could be seen. 'Attention, hostiles
approaching!'
      K9 drew back, and Leela took shelter behind a chunk of rubble.
      Lowe appeared, with Cruickshank and a number of other
Centre staff behind him. All had the metallic rash around the eyes,
and all were carrying blasters.
      Lowe raised a hand to halt his little army. 'It is the reject.' He
moved cautiously forward and peered across the barrier. 'Leela,' he
called. 'Leela! Bring me the Doctor!
      'Come and get him,' shouted Leela, and opened fire.
      Lowe and his men fired back, and a fierce blaster-battle raged
across the barricade.

      The Doctor moaned and writhed in his bonds. Marius checked
his wrist chronometer. 'Less than eight minutes to go. Anything,
Parsons?'
      Parsons was studying Leela's tissue sample under a
computerised electron microscope, in the desperate hope of finding
some explanation of her immunity from the disease. He studied the
computer read-out screen. 'It's all here, sir. Leela's tissue profile,
adaptation, disease resistance...'
      'Bit of a mongrel, isn't she,' said Marius thoughtfully. 'Probably
explains why her race survived. But no sign of any physical
immunity.'
      'There's a wide range of possible blood characteristics, sir,' the
nurse pointed out. 'It will take hours to check them all.'
      'On the other hand it could be a psychological factor,' mused
Marius. 'Something in her mind, her way of looking at things.'
      There was a crackle of blaster-fire from outside the room. and a
yell of triumph from Leela as she scored a hit. 'Aggression?'
suggested Parsons.
      'Determination, stamina,' said Marius. 'The predator's instinct!'
       Leela ducked instinctively as another thought-flash whizzed
over her head.
       The Doctor looked proudly around him. 'You'd never think it
was the most advanced computer system ever, would you?'
       Leela pointed to a glowing, knotted mass of tissue hanging just
ahead of them. 'Ugh, what's that?'
       '"That is why my brain is so much superior to yours,' said the
Doctor huffily. 'It's a super-ganglion.
       Leela wasn't listening. 'Doctor, I can sense danger,' she
whispered.
       'Rubbish! If there was any danger about, I'd be the first to sense
it. I know this brain like the back of my hand. What do you know
about brains anyway?'
       'All right, all right, don't get excited,' said Leela. It was a pity
the Doctor's bad temper had been cloned along with the rest of him.
       'I'll get excited if I like, it's my brain! Do you want to know
something?'
       'Not particularly!
       'Well, I'll tell you anyway. Somebody once tried to build a
machine as efficient as the brain. Trouble was, it would have had to
be bigger than London—you remem ber London?—and powered by
the entire European grid. And that was only a human brain, mine is
much more complex. Left and right side working in unison via these
specialised neural ganglia, thus combining data storage retrieval with
logical inference and the intuitive leap—' The Doctor broke off. 'Are
you listening, Leela?'
       'Yes,' said Leela, though she'd hardly heard a word.
       They'd reached another massive complex of glowing, twisted
ganglia. The Doctor pointed, rather like a guide displaying the crown
jewels. 'That is the reflex link,' he said impressively. 'With that I can
tune myself in to the Time Lord intelligentsia—a thousand
superbrains in one!
       'Why don't you do it then?' suggested Leela. She was beginning
to get tired of being lectured. As far as she was concerned, they
needed all the help they could get.
       The Doctor coughed. 'Ah well, as it happens, I lost that
particular faculty when they kicked me out...'
       'They kicked you out?' asked Leela, intrigued. She knew little
of the Doctor's past history.
       The Doctor was studying another tangle of ganglia further
down the tunnel. 'Come and look here, Leela, these connections have
been severed.' The Doctor studied the rent. 'Hullo...'
       Leela popped her head through the other side of the gap.
'Hullo!'
       'Don't be funny,' said the Doctor disapprovingly.
       'Doctor, you're wasting time, we've got to keep moving in.'
       'No, don't you see, this is recent damage, Leela.'
       'The virus?'
       'What else? We must be getting close!
       A white blob dropped from nowhere to land on Leela's
shoulders. She screamed and tried to throw it off, but another
followed, and then another, until she was covered in the billowing
globular shapes. 'Doctor, help me,' she screamed.
       'I can't! It's my body's defence mechanisms, my own
phagocytes. Use your knife!'
       Leela drew her knife and slashed desperately about her, but the
number of attacking phagocytes seemed limitless, and soon she
disappeared from view buried beneath the seething white forms.
       With sudden inspiration, the Doctor dashed to the opposite side
of the tunnel, grabbed two dangling nerve-ends and thrust them
together. There was a crackle and a flash, and suddenly the army of
phagocytes began moving away from Leela, disappearing down the
tunnel as if summoned by some distant alarm.
       The Doctor helped her to her feet.
       'What did you do?'
       'Gave them a faked alarm call. I think I told them my liver was
disintegrating!'
       'That's very clever, Doctor! '
       'I know it's very clever,' agreed the Doctor. 'Come on!'
      In the isolation ward the Doctor struggled to reach the small of
his back. His whole body arched and he gave a groan.
      'What's happening?'
      Marius shrugged. 'No idea. But it proves they're in there...
some sensitive area...'
      They heard more blaster-fire from the corridor out-side. It was
closer now, as though K9 and Leela were being driven back.
      Marius looked at the chronometer. 'Seven and a half minutes to
go.' He sighed..'Not much chance of success now...'

       Lowe's attacking army seemed to be unlimited. Between them
Leela and K9 had shot a good many down, but there were always
others who stepped forward to take their place. Lowe and his aides
seemed to have managed to infect most of the staff of the Centre
between them.
       Cruickshank, more infected and more fanatical than the rest,
hurtled over the barrier in a desperate leap—and K9 shot him down.
Cruickshank fell dying directly in front of K9—and a sudden
lightning-flash crackled between his eyes and K9's eye-screen.
       In a slurred, dragging voice K9 said, 'Contact has been made—
Master...'
       From the other side of the barrier Lowe screamed, 'Kill her,
K9! Kill the reject!'
       'Affirmative. Kill the reject,' droned K9 obediently. He swung
round. Leela was moving about further along the barricade, ducking
from one piece of cover to another, returning the fire of Lowe and his
men.
       Vastly outnumbered, she was enjoying herself enormously.
       Absorbed in her battle, she didn't notice K9 gliding towards
her, the nozzle of his blaster aimed at her back...
                                8
                            Interface
       The Doctor paused at a gaping, blackened split in the tunnel
wall. 'After you, Leela.'
       'Are you afraid?'
       'Not necessarily,' said the Doctor a little defensively. 'But from
now on we're right on the trail of the virus. That's the path it took.'
       'Where to?'
       'Well if I knew that I wouldn't have brought you along. This is
where your tracking skills come in.'
       Leela nodded and drew her knife. She slipped through the dark,
sinister-looking gap, the Doctor close behind her.

       Not for the first time, Leela's uncanny instinct saved her life.
Sensing danger she swung round—to find K9's blaster covering her.
K9 fired, but she was already hurling herself through the air in a
flying leap. K9's blaster-bolt missed, and Leela landed awkwardly.
She twisted her foot on a chunk of rubble, and pitched forward. Her
head thumped against the wall.
       K9 wheeled to face Lowe who was clambering over the
barricade. In a slurred voice K9 said, 'Reject liquidated. K9 into self-
regeneration—non-functional...' K9's eye-screen went dim, and all his
antennae drooped. He glided slowly over to the wall beside Leela,
bumped his nose against it and stayed motion-less.
       Lowe dropped down over the barricade, saw the knocked-out
Leela and drew the obvious conclusion. The reject was dead, the
automaton de-activated. He had no further interest in either of them.
'Good—and now for the Doctor,' he whispered exultantly. He headed
for the door of the isolation ward.

       Leela said, 'Ouch! ' and clutched the back of her head. 'What is
it, Leela? What's the matter?'
       'Something banged my head... a real thud...'
       'Not in here, Leela, that must have been your outside head.'
       'Oh, well, that's all right then.'
       'No it isn't,' said the Doctor seriously. 'You and I have only got
a limited life in here as it is. Your outside self and your inside self are
made of the same tissue. If your outside self is hurt, then you feel the
shock. And if your outside self is killed...'
       Leela shuddered. 'We'd better make the most of the next six
minutes then.'
       They moved on their way, following the blackened trail of
virus damage. It was very plain now, and it led them at last to what
looked like a colossal chasm. Into the chasm projected a kind of
bridge, a narrow strip of tissue arching up into the darkness. But the
bridge stopped, abruptly, half-way across. It was a bridge to nowhere.
A rushing wind filled the air, howling through the depths of the
chasm.
       'Where are we?' whispered Leela.
       'This is the gap between one side of my mind and the other.'
       'But it's dark on the other side!'
       'Well of course it's dark, Leela. It's the gap between logic and
imagination. You can't see one side from the other side.'
       'But it is there? There is something on the other side?'
       'This is the mind-brain interface, Leela—at least, I think it is.'
The Doctor gestured expansively. 'There's the mind and there's the
brain. Two things entirely different, yet part of the same thing.'
       'Like the land and the sea?'
       Pleased with her understanding, the Doctor said, 'That's right,
Leela. That's exactly right!'
       Leela stared down into the chasm. 'It's very deep!'
       The Doctor looked thoughtfully into the darkness of his own
unconscious mind. 'Yes... sometimes I don't quite understand it
myself!'
       Giving Leela one end of his scarf to hold, the Doctor began
edging his way across the narrow bridge.
       Leela followed nervously. The ridge of tissue was appallingly
narrow and it felt spongy and unreliable beneath her feet. The wind
howled around her, plucking at her clothes. Several times she came
close to losing her balance.
       When he got to the point where the bridge appeared to vanish
the Doctor stepped confidently off into blackness. He vanished. His
scarf vanished too, except for the section Leela was holding. Leela
hesitated. "There came an indignant tug from the invisible Doctor on
the end of the invisible bit of scarf. Leela closed her eyes and stepped
off into nothingness...

      Marius looked at his chronometer. 'Five minutes to go...' he
said despondently.
      'Don't move, Professor,' said a harsh triumphant voice. Lowe
was covering him from the doorway.
      Parsons made a desperate attempt to reach the blaster under his
gown. Lowe swung his blaster and shot him down. He turned the
blaster back on Marius. 'Release the Doctor.'
      'No,' said Marius defiantly. 'No, I can't!'
      Lowe came menacingly forward. When he stood face to face
with Marius, a jagged lightning-streak flashed between his own
forehead and the professor's.
      'Release him,' said Lowe again.
      In a slurred, dragging voice Marius said, 'Contact has been
made.' He moved to unfasten the straps.
      (Unseen, Marius's nurse crouched down behind the cloning
booth, too terrified to move.)
      'We must make contact with the Nucleus,' said Lowe eagerly.
      With the virus in control of his mind, all Marius's loyalties
were now devoted to the Purpose. 'No, wait,' he said. 'The Nucleus is
in danger.'
      'What?' snarled Lowe.
      Marius's words seemed to come tumbling out. 'Micro-cloned
copies have been injected into the brain to hunt down and destroy the
Nucleus... If they succeed...'
      'They must not succeed!'
      'We can't stop them,' babbled Marius. 'There is no time.'
      'I say we must! ' roared Lowe. 'We must! '
      (Unseen, the nurse began edging towards the door.)

       Outside in the corridor, K9 came slowly back to life. Leela,
too, was beginning to revive. K9 glided up to her and sent out a probe
from his head to touch her forehead. 'Mistress! ' he called.
       A mild electric tingle brought Leela to full consciousness, and
she scrambled to her feet. 'Why did you attack me?'
       'I had to. I was temporarily overpowered, and my motivational
circuits were in confusion. I have now fully regenerated, and await
your further orders—Mistress.'
       'Where are our enemies? Have they captured the Doctor?'
       Sadly K9 said, 'Affirmative, Mistress.'
       Suddenly the nurse slipped out of the isolation ward and ran
down the corridor towards them. 'They've got Professor Marius—he's
been taken over by the virus. They've killed Doctor Parsons...'
       She began to sob. Leela grabbed her by the shoulders and
shook her hard. 'What are they doing now?'
       'They're cloning Lowe. Marius is going to inject him into the
Doctor's brain.'
       Leela headed for the ward door. 'We'd better stop them.'
       K9 glided forward to bar her way. 'Negative!'
       'Why?'
       'We cannot interfere while there is still a possibility that the
micro-clone of the Doctor will succeed in destroying the Nucleus.
We must wait. '

      The micro-cloned Leela found herself following the Doctor
across the other side of the narrow bridge. The only difference was
that now instead of not seeing where she was going, she couldn't see
where she'd been. The brain storm howled round them with renewed
force now, and she wondered when the other side of the chasm would
come in sight.
      'Bracing, isn't it?' shouted the Doctor.
      'Very!' said Leela grimly.
      The Doctor looked around him. They were facing a great cliff
of sheer, solid blackness. There was blackness above and below
them, blackness on every side. 'Magnificent, isn't it? The interface!
The mind, un-sullied by a single thought!'
      'Where are we going?' asked Leela practically.
      'Into the land of dreams and fantasy, Leela..

      Professor Marius bent over the deformed body of the Doctor, a
hypodermic in his hand. The colourless fluid inside it held the micro-
cloned body of Lowe. Carefully Marius injected the fluid into the
Doctor's head...
      A horrible gurgling voice came from the Doctor's twisted
mouth. 'Hurry, hurry. They are closing in. Hurry, hurry, hurry...'

      With the panic-stricken voice of the Nucleus urging him on,
Lowe raced through the Doctor's brain. He forced his way through
the blackened split in the neural tissue, and raced recklessly across
the narrow windswept bridge...
      The Doctor and Leela meanwhile were forcing their way
through a tunnel in what looked and felt like black, shiny rock. 'Is this
your land of dreams?' asked Leela.
      'Well, on the way to it...'
      They emerged from the cleft into an enormous cavern, bigger
than a thousand cathedrals. Huge silver pillars stretched away into the
immeasurable distance.
      Near-by, on the floor of the cavern, was a twisted honeycomb
of rock, a strange distorted growth that was obviously out of place.
      'There it is,' said the Doctor quietly. They began hurrying
towards it. As they came closer, Leela could see that something
living was stirring inside the rock. She caught a glimpse of lashing
tentacles, the evil gleam of a bulbous eye.
      'The evil thing,' breathed Leela. She paused to listen. 'And
another follows, close behind us, Doctor. We're trapped!'
                                 9
                               Nucleus
       Before the Doctor could speak, Leela drew her blaster and ran
back towards the tunnel.
       The Doctor walked forward to confront his enemy. As he got
closer to the twisted honeycomb, he saw through the many holes and
gaps that some strange living creature seemed to permeate the whole
structure. He saw waving antennae, glistening wet red flesh, and a
bulbous black eye that. seemed to swivel to and fro in search of him.
From the little he could see, thought the Doctor, it was probably just
as well that the rest was concealed.
       He strode up to the rock and said, 'Hullo! Who are you?'
       A slobbering, gurgling voice said arrogantly, 'I am the
Nucleus!'
       'You're trespassing, you know,' said the Doctor reprovingly.
'Disturbing my unconscious, affecting my metabolism—' He paused.
'Nucleus of what?'
       'The Nucleus of the Swarm,' gurgled the voice.
       'I see,' said the Doctor thoughtfully. Then he napped, 'Why did
you choose my brain?'
       'Because of your intelligence.'
       'Well, I can understand that,' said the Doctor. 'But you've no
right—'
       'I have every right,' interrupted the hateful voice. 'It is the right
of every creature across the Universe to survive, multiply and
perpetuate its species... How else does the predator exist? And we are
all predators, Doctor. We kill, we devour to live. Survival is all! You
agree?'
       'Oh yes, I do. And on your own argument, I have a perfect right
to dispose of you.'
       'Of course! The law is survival of the fittest!'
       A long whip-like tentacle lashed out at the Doctor's face,
nicking his check. The Doctor touched the cut, and looked at the little
smear of blood on his fingers. ' Touché!' he said wryly.
       'Your time is running short,' sneered the Nucleus. 'How do you
intend to dispose of me? You have no weapons and in minutes you
will cease to exist!'
       The Doctor said nothing. The Nucleus began a long, ranting
speech of self-justification. 'I am the Virus and the Nucleus of the
Swarm. For millennia we have hung dormant in space, waiting for
the right carrier to come along...'
       This was too much for the Doctor. 'Carrier?' he said
indignantly. 'What do you mean, carrier? I'm not a porter!'
       The Nucleus ignored him. 'Consider the human species. They
send hordes of settlers across the galaxy to breed, multiply, conquer
and dominate. We have as much right to conquer them, as they have
to strike out across the stars.'
       'But you intend to dominate both worlds,' said the Doctor
sombrely. 'The micro- and the macro-cosm.'
       'We have waited, waited,' said the gloating voice.
       'Waited in the cold wastes of space for mankind to come. Now
we have not only space but time itself within our grasp! '
       'Time?'
       'Through you—Time Lord!'
       So, thought the Doctor grimly, the Nucleus knew. Now more
than ever it had to be destroyed...

      Leela waited in the long black tunnel, knife in hand. She could
almost sense the approach of her enemy.
      A figure lurched into view and she sprang—then jumped back
in horror. A mass of pulsing white phagocytes was covering Lowe's
body. Only his incredible fanaticism could have enabled him to keep
moving.
      Leela hesitated, knife poised, looking for the human target
under the pulsating mass. Somehow Lowe managed to fire, and a
blaster-bolt scared Leela's side. She staggered back, drew her own
blaster, and fired again and again. Lowe's body slumped down, and
the phagocytes swarmed over it, devouring it. Leela ran back along
the tunnel.

       'So, Doctor,' concluded the Nucleus triumphantly, 'How can
you puny creatures compare yourselves to us, the Swarm? The new
masters of time, space and the cosmos!'
       'New masters?' said the Doctor grimly. 'Not if I can help it!'
       'But you cannot! Your time is up. You have fallen for my
stratagem. Already you cease to exist! '
       The Doctor touched a hand to his face. It felt insubstantial,
paper-thin... He could feel cracks appearing. Too late the Doctor
remembered that he was only a carbon copy with a strictly limited
life—a life that looked like ending before its work was done...
       Leela came staggering back into the great cave, blaster in hand,
and the Doctor shouted, 'Leela, the blaster! Give it to me!'
       She threw it, the Doctor caught it and swung round to fire at
the rock. Already the black rock was splitting as the Nucleus
struggled to escape... Eyes dimming, hand shaking, the Doctor fired
at the rock, muttering, 'Get out of my brain! Get out of my brain...'
The blaster dropped from his hand. He staggered and fell.
       Leela ran to kneel beside him. Her body was dry and cracking
too, and she could feel herself fading away. 'Has it gone, Doctor?'
       The Doctor pointed. The honeycomb rock was smashed to
pieces, and the fragments were rapidly crumbling to black dust. Of
the Nucleus there was no sign.
       The Doctor struggled to rise. 'The tear duct,' he muttered. 'Must
get to the tear duct...'
       Leela tried to help him, but he faded away in her arms, leaving
only a bundle of clothes and a long scarf. Then these too vanished.
       Next, Leela herself vanished. For a moment a knife and a lock
of long hair lay on the cavern floor, then faded and vanished. The real
Doctor and Leela, the originals, were still alive and struggling in the
Foundation, but their carbon copies were no more.
       Something red and glistening scuttled away through the
caverns of the Doctor's mind... towards the tear duct.
        The Doctor's face was almost entirely covered with the metallic
rash by now. A tear welled from the corner of one eye. Marius, his
own face affected by the rapidly spreading virus, caught the tear on a
glass rod and transferred it to a glass dish.
        Lowe, the real Lowe, glared malevolently at the tiny drop of
fluid. 'Destroy them. Destroy them now!'
        Marius shook his head. 'No. We must find out what happened
in there. We must restore them to their full size and interrogate them
while there is still time...'
        He carried the dish over to the cloning booth, reversed the RDS
controls as the Doctor had shown him, switched on the machine,
closed the booth door and stepped back.
        There was a hum of power, and a shape began to form inside
the booth. But it was not the shape of the Doctor or Leela... It was not
a humanoid shape at all...
        At the same time the signs of the virus infection were receding
from the Doctor's face with incredible speed. Soon he was completely
himself again. His eyes opened and he looked round alertly.
        Lowe opened the door. and stepped back reverently. A
horrible, incredible shape was filling the booth. It was blood-red in
colour and was as big as a man with a bony glistening body and
lashing tentacles. The huge black bulbous eyes swivelled
malevolently around the ward. The Doctor's RDS had magnified the
Nucleus to full human size.
        'Help me,' gurgled the creature. 'Help me out.'
        Lowe and one of his infected aides went to help.
        'Marius! ' hissed the Doctor.
        Marius swung round, and the Doctor saw the virus-rash
overspreading his face. 'Oh, no,' he groaned.
        'Yes, Doctor,' said Marius complacently. 'Contact has been
made. Now I serve the Purpose!'
        The Doctor looked at the pulsating creature being lifted from
the booth. 'What? And that pathetic crustacean is your leader?'
        'You are speaking of the Nucleus, the Nucleus of the Swarm,'
snarled Marius.
        'Take me to him,' ordered the Nucleus.
       Lowe and an aide lifted the horrible creature and carried it
across to where the Doctor lay on his couch. The Doctor studied the
Nucleus thoughtfully. It didn't look as if it could move or even stand
unassisted. Perhaps it hadn't grown fully used to its new size. No
doubt in time it would adapt. grow strong... 'Finding the macro-world
difficult?' enquired the Doctor affably.
       'Soon it will suit me well,' promised the Nucleus. 'I thought I'd
got rid of you!
       'You were mistaken. I made use of your escape route, through
the eye.'
       'Yes, you'd have known about that,' said the Doctor
thoughtfully. 'Snooping about in my mind...'
       'Another mistake, Time Lord—and a costly one for you. Now,
thanks to your dimensional stabiliser, I am no longer forced to remain
in the micro-world to breed and multiply. My Swarm, when it is
hatched on Titan, will no longer take the form of invisible microbes,
weak and prey to all, but mighty and invulnerable creatures.
Invincible! The Age of Man is over, Doctor. The Age of the Virus
has begun!'
       'I've heard all that before,' said the Doctor scornfully. 'You
megalomaniacs are all the same!'
       Angry at the Doctor's blasphemy, Marius leaned over him,
staring hard into his eyes. A lightning-tentacle flashed between his
eyes and the Doctor's—and rebounded on to Marius again. He
staggered back.
       The Doctor felt a sudden surge of hope. He was immune!
Perhaps because he'd survived such a massive attack, perhaps for
some other reason, the virus could no longer take over his mind. Now
he could really fight back.
       His relief was short-lived. Lowe stepped forward, face twisted
with anger, raising his blaster.
       'No, not yet,' commanded the Nucleus.
       Apparently, it felt that a quick death was too good for the
Doctor. 'We shall take him with us to Titan—to be consumed by the
Swarm!'
                              10
                         The Antidote
       Leela looked admiringly at herself in the mirror set into the
locker door. She'd broken open a first-aid locker in the reception area,
and was using a random assortment of ointments and dressings to
produce a fair approximation of someone in the first stages of virus
infection. A nurse's robe she found hanging in another locker
completed her disguise. 'How do I look, K9?'
       'Friend, Mistress,' said K9, failing to understand her question.
       Leela checked the blaster hidden under her robe. 'If I can just
get close enough to that Nucleus, it'll see how friendly I am.'
       'Hostiles approaching, Mistress,' warned K9. 'With the Doctor.'
       They ducked into a doorway for cover.
       An extraordinary procession was coming down the main
corridor. First came the heaving, pulsating Nucleus, its breath
gurgling liquidly in its throat. Lowe and a medic were supporting it
between them. Behind them came the Doctor, firmly strapped down
to a hospital trolley, pushed by Marius.
       The Nucleus was growing impatient. 'Hurry! Hurry! It is time
for the spawning. I must go to the place prepared on Titan.'
       From the corner of his eye Marius caught sight of Leela's
uniform. 'Nurse, take over here. I must assist with the Nucleus!
       Hesitantly Leela came forward. Marius showed no signs of
recognising her, perhaps because of her disguise, perhaps because
personality meant little to those who served the Purpose. Marius let
Leela take over the pushing of the trolley, while he went to help
Lowe and the others with the cumbersome, constantly complaining
Nucleus.
       The Doctor looked up. 'Your eye make-up's running, Leela! '
he whispered.
       'Ssh! ' reproved Leela. She slipped the knife from under her
coat and began sawing at the Doctor's bonds.
       By the time they reached the TARDIS, standing forgotten in its
corner, the Doctor was free.
       With a sudden shove, Leela whizzed the trolley towards the
TARDIS door.
       Marius turned. 'Nurse, not that way!'
       But it was too late. The Doctor sprang from the trolley, opened
the TARDIS door and leaped inside. K9, who had been lurking
behind the TARDIS, whizzed round to the front and followed the
Doctor in. Hampered by the cumbersome Nucleus, it took Lowe and
Marius too long to react. Lowe detached himself from the group and
raised his blaster. Leela fired a quick blast at random. It missed, but it
was enough to spoil Lowe's aim. The blaster-bolt sizzled harmlessly
over her head, and seconds later she was safe inside the TARDIS
with the others. The door closed behind her.
       'They have escaped,' screamed Lowe.
       'They are trapped,' corrected the Nucleus. 'Without its missing
component. the Doctor's craft cannot move. Marius, you will stay
here, to make sure the Doctor does not escape. Recruit other host
bodies. When the Doctor emerges, recapture him, and join us on
Titan.'
       Marius bowed his head in assent.
       Lowe and the others carried the Nucleus towards the airlock. A
Foundation shuttle craft stood fuelled and ready in the departure bay.
Soon the Nucleus would be on Titan, and the spawning could begin.

      Thankfully Leela peeled off the last of her disguise. 'Well,
Doctor, now what?'
      'Now nothing,' said the Doctor gloomily. He was watching the
airlock door on the scanner, as it closed behind the Nucleus and its
attendants.
      'Doctor, if we can get to Titan first we can still beat that
horrible thing.'
      'Well, we can't. The dimensional stabiliser's still in the isolation
ward. Without it the TARDIS won't move an inch.'
      'So there's nothing we can do?' asked Leela disgustedly.
       'Did I say that, K9?' The Doctor looked down. K9 was gliding
inquisitively round the TARDIS control room, pausing to sniff, or
rather to sense, various interesting pieces of equipment. 'Listen to me,
K9! Do you think you could go out there and poleaxe Marius?'
       K9 said 'Query: please clarify term "poleaxe".'
       'Knock him out!'
       'Affirmative. My weaponry has four levels of intensity. Kill,
stun, paralyse...
       'No, no, no, not kill. Just knock him out, eh?'
       'Affirmative.'
       'Good dog! '
       The Doctor looked at the scanner screen. After hovering
indecisively for some time, Marius was heading for the reception
desk.
       'Off you go then, K9.' He opened the TARDIS door and K9
glided out.
       Marius was at the reception desk microphone. 'All senior staff
to reception. This is Professor Marius. Senior staff to reception...' He
looked down coldly as K9 approached. With the virus now
controlling his mind, Marius could no longer understand the streak of
sentiment that had caused him to want a computer in the shape of a
dog. 'K9,' he said coldly, 'I no longer need you.'
       K9 blasted him, and Marius slumped to the ground. The Doctor
and Leela rushed from the TARDIS, picked up Marius, threw him on
to the trolley that had been used for the Doctor, and whizzed him
away.
       The trolley sped along the corridors and shot into the isolation
ward. The Doctor burst into a flurry of activity. He took a blood
sample from his own finger, mounted it on a slide, then turned to
Leela. 'Your turn, Leela, finger! Quickly, we haven't got a moment to
spare.'
       Leela winced as the Doctor pricked her finger with the little
scalpel.
       The Doctor smiled. 'Come on, Leela, not frightened of a spot of
blood are you—mighty hunter! '
       'Just hurry up,' said Leela, sucking her finger.
       The Doctor mounted Leela's blood sample next to his own and
slid the slide into the computerised electron microscope. Leela
watched him, baffled. 'Haven't we been through all this before?'
       'I had the virus then—I'm immune now. Something must have
happened while you and I were inside my head. I want to find out
what!' The Doctor switched on the microscope's read-out screen and
studied it absorbedly. 'Ah, now that's very interesting.'
       Leela looked at the swarming patterns on the screen, her blood
sample and the Doctor's side by side. To Leela they looked
completely different—but not to the Doctor.
       He leaned forward and tapped the screen. 'See that fish-hook
shape wriggling about? That's an antibody, the only one you and I
have in common. I didn't have that before, so it must be the immunity
factor.'
       'How did what I have get into your blood?'
       'Quite simple. Your clone. which was produced from your
tissue, was absorbed into my bloodstream and passed on the
immunity to me. All we've got to do is isolate it, analyse it, duplicate
it, and inject it into Marius here, and he in turn will be able to cure all
the others.'
       Leela couldn't believe things were quite that simple. 'What
about the Nucleus? What about Titan?'
       'One thing at a time, Leela,' said the Doctor reproachfully. 'One
thing at a time!'

       The Foundation shuttle, sides marked with the red cross, was
carrying its strange passengers towards Titan. Lowe was at the
controls, while the Nucleus was pulsating on an acceleration couch,
surrounded and supported by its taken-over aides. 'Faster, faster!'
roared the Nucleus. It was in a slavering frenzy of impatience.
       'We can't,' said Lowe. 'Any faster and the motors will burn out.'
       'Let them burn out. Once we reach Titan and the breeding
tanks, your task is finished.'
       'What about the Doctor?'
       'He will follow us to Titan, a prisoner. Marius will make sure
of that. Faster, now. Use all the fuel! Faster!'
      Obediently Lowe thrust the speed-control lever to maximum.
The shuttle surged forward with a roar that shook the little cabin.

       The Doctor and Leela hovered anxiously over Professor
Marius. He had been injected with the antidote some time ago. Now
they were waiting to see the results.
       'It's working,' whispered Leela. 'Look, Doctor!'
       With incredible speed the virus rash was receding from
Marius's face. Soon it was completely back to normal.
       'Sometimes my brilliance astonishes even me,' murmured the
Doctor modestly. 'Come on, Marius, wake up, wake up!
       Marius opened his eyes and peered blearily at them. 'What
happened?' He sat up and looked round. 'Where's Parsons?'
       'Dead, I'm afraid. Do you remember anything?' Marius
frowned. 'I remember Lowe coming in. then there was a flash... then
nothing... Doctor, did the experiment work?'
       'Yes—and no,' said the Doctor ruefully. 'Unfortunately, the
Nucleus got away, and the dimensional stabiliser increased it to
human size. It's on its way to Titan to breed.'
       'And was I taken over?' Marius rubbed a hand over his face,
relieved to find it normal.
       'Yes, it got you, for a while, Professor. But we've found the
immunity factor. So we're safe here, at least for the time being...'
       Marius was overjoyed. 'The immunity factor? What was it?'
       'It was something in Leela, something we all missed.' He
handed Marius a phial of milky liquid. 'This is the antidote, but you'll
have to make a great deal more. And Professor, if those antibodies
can confer immunity, they can be developed to attack the Nucleus! '
       'Attack the Nucleus?' said Marius, alarmed. 'That will be highly
dangerous, Doctor.'
       'Of course it's dangerous! But if we allow the Nucleus to breed
and swarm, it will go through the entire galaxy like a plague of giant
locusts.'
       'But even if we develop a way to destroy the virus, will you be
able to get it to Titan on time?'
      'Yes!' said the Doctor triumphantly. He crossed to the booth
and picked up the complex electronic equipment. 'Now I've got this
back, we can use the TARDIS...'

       The huge bubbling tank was completely walled-in, the only
entrance by a heavy metal door.
       Safran looked through the thick plasti-glass viewing window
set into the door. The giant tank was filled with a bubbling, seething
fluid. He studied a control panel beside the door. Temperature,
nutrients, atmosphere, all were exactly right.
       With a smile of pride, Safran crossed to a space-radio set up in
the corner and leaned over the speaker-microphone. 'Safran on Titan.
Safran on Titan. The Hive is prepared. The breeding tanks are ready.
Temperature and humidity are set.'
       Safran glanced back proudly at the seething, glowing tank. 'I
await your arrival—and the generation of the Swarm!'

       The entire control cabin was shuddering with the speed of the
shuttle's flight. But still the Nucleus was not satisfied. 'Faster, faster!'
it screamed.
       'There is no more I can do,' shouted Lowe helplessly. 'We have
already reached maximum speed!'
       'We must go faster, Lowe,' it roared. 'The time for spawning is
very close...'
       The shuttle sped on. As soon as it arrived on Titan, mankind
would be doomed...
                               11
                            The Hive
       The isolation ward was a scene of bustling activity again.
Leela, the Doctor and K9 had been scouring the Foundation for
infected medics, knocking them out, and dragging them back to the
isolation ward where they were forcibly injected with the antidote.
When a sufficient number of medics had been cured, they were set to
work manufacturing supplies of the antidote and sent out in teams to
cure their fellow workers. It would be a long time before everything
was back to normal, but slowly the Foundation was coming back to
life.
       Leela had quite enjoyed that part of the proceedings, but now
she was restless again. The Doctor and Marius were busily trying to
produce a killer-virus that would destroy the Nucleus and its Swarm.
It seemed to be a very long and complicated business, and Leela soon
grew tired of watching masked and robed medics bustling about with
dishes of virus-culture.
       'How much longer, Doctor?' she asked impatiently.
       The Doctor was absorbed in his work. 'Can't rush these things,
they're breeding them as fast as they can. K9's linked to the
computer-microscope. He'll tell us when we've got the most powerful
strain.'
       Leela brooded for a while. 'Why don't we just blow up Titan?'
she suggested cheerfully. 'Nucleus, breeding tanks and all! '
       The Doctor looked reprovingly at her. 'That's your answer to
everything, isn't it? Knock it on the head!'
       'Well, it's effective, isn't it? Smash it, once and for all...'
       'With what?' demanded the Doctor. 'This happens to be a
hospital, not an arsenal!'
       'All right,' said Leela sulkily. 'How are you going to fight it?'
       K9 bustled forward importantly. 'Confirm strain C531 has
optimum lethal capacity.'
       Marius hurried up to them, in a state of great excitement.
'Doctor, we've done it! Congratulations!' He turned to his assistants.
'Manufacture a batch of C531 immediately. Hurry now, there isn't a
moment to be lost!'
       The Doctor leaned down and patted K9 on the head. 'Thank
you,' he said solemnly.
       Leela was impatient. 'And now what?'
       'We just chuck it into the breeding tank, and wait for it to
attack the Nucleus the same way the virus attacked us...
microscopically! Neat, don't you think?'
       'Oh, is that all?' asked Leela satirically. 'If we can get to Titan
in time, if we can get past Lowe and the others, if it works when we
finally let it into the breeding tank ' She checked herself. 'I thought
you didn't like killing?'
       'I don't.'
       'Then why are you doing all this?' asked Leela, confident she'd
caught the Doctor out for once.
       'The virus has a perfect right to exist as a virus—but not as a
giant swarm threatening the galaxy. Everything has its place.
Otherwise the delicate balance of the whole cosmos is destroyed!'
       'I still say we should blow it up,' muttered Leela sulkily.
       Marius came hurrying forward, holding a vacuum-container.
'Doctor, the batch is complete!'
       The Doctor took the container in his hands, and stood looking
down at it for a moment. 'Good! Now for the TARDIS!'

       The Nucleus emerged from the airlock on Titan Base and
moved slowly and painfully along the corridors, assisted by its
solicitous helpers.
       Safran stood waiting at the door of the giant fuel tank. Proudly
he opened the hatch and the Nucleus heaved itself to the brim of the
tank. 'Remember,' said the gurgling voice, 'I must be protected while
I am in the Hive. The future of the Swarm depends on you!'
       Lowe and Safran and the aides bowed their heads in reverence.
The Nucleus disappeared into the seething tank of nutrient.
      Safran stepped back, and closed the door reverently. The
breeding of the Swarm was about to begin.

       The Doctor and Leela paused by the open door of the TARDIS
to say good-bye to Marius and K9. 'Good luck, Doctor,' said Marius.
       'Thank you.' The Doctor turned to enter the TARDIS and then
paused. 'Oh Professor?'
       'Yes?'
       'I don't suppose we could borrow K9, could we?' asked the
Doctor hopefully.
       'Borrow K9—what for?'
       'I've got used to having him around—and he can be very
useful.'
       'Of course, I understand.' Marius looked down. 'K9! Obey the
Doctor.'
       'Affirmative,' said K9 happily, and disappeared into the
TARDIS.
       Marius stepped back, the TARDIS door closed and a few
minutes later there was a strange, wheezing, groaning sound. The
TARDIS disappeared. Marius blinked in mild surprise, and then
hurried away. There was still a great deal to do before the Foundation
could be got back to normal.

       Lowe moved along the gloomy, winding corridors of Titan
Base, followed by his medics. All were armed with blasters, and
Lowe posted a guard at each main intersection.
       When he was satisfied his defences were complete he returned
to the great fuel tank and looked through the viewing window.
       The Nucleus lay inert, pulsating gently in a sea of bubbling
grey jelly. Surrounding it were thousands upon thousands of eggs,
round and white, as big as tennis balls. They lay floating on the
seething tank of jelly awaiting the moment when it was time for them
to hatch...

     By means of a rather nifty feat of navigation, the Doctor
managed to materialise the TARDIS in Supervisor Lowe's office. The
visiphone screen showed the interior of the breeding tank. The
Doctor studied the seething mass of eggs. 'The breeding season's
already under way!
       Leela stared at the screen in alarm. 'Doctor, what is it?'
       'It's the Swarm—and it's starting to hatch. We must hurry!'
       The Doctor looked out of the office door, and then stepped
back.
       'What's the matter?' whispered Leela.
       'There's a guard coming. He must have heard the TARDIS...'
       Leela motioned to the Doctor to step back, and waited, drawing
her blaster.
       'Come in! ' shouted the Doctor cheerfully.
       The guard stepped through the door, blaster at the ready. Leela
fired. The guard staggered back. Incredibly he didn't fall, even though
he'd been shot at point-blank range. Slowly, painfully, he raised his
blaster to cover Leela. She fired again but there was no effect. It
wasn't until K9 glided forward and added his blaster-fire to her own
that the guard staggered, and finally fell.
       'Thank you, K9,' said Leela. 'Doctor, what went wrong? Why
didn't my blaster work?'
       The Doctor was kneeling by the fallen guard. The man was in
an advanced stage of viral infection, face and hands almost covered
by the growth of stiff, metallic hair. 'Their internal cell structure must
be changing. They're developing a resistance to radiation—'
       'Master, I have a problem,' K9 broke in suddenly.
       'Offensive capability seriously diminished, reserves... very
low.' K9's eye-screen went dim, all his antennae drooped, and he
became very still.
       'K9's breaking up, my blaster's finished,' said Leela worriedly.
'Doctor, what are we going to do?'
       'Shall we try using our intelligence?'
       'Well, if you think that's a good idea,' said Leela dubiously.
       The Doctor was already disappearing down the corridor. 'Come
on,' he shouted. 'And you, K9.'
       Leela ran after the Doctor and K9 glided after them.
       They hadn't got very far before they carne to another
intersection—and another guard. They flattened themselves back
against the wall, and the Doctor whispered, 'K9, you see that guard?'
       'Affirmative.'
       'I want you to decoy him.'
       K9 glided into view. The astonished guard stared for a moment
and then raised his blaster. K9 zig-zagged wildly, the blaster-bolts
missed, and K9 vanished down the corridor with the guard in pursuit.
       The Doctor and Leela moved cautiously on. At the end of the
corridor was a gloomy shadowed cavern lined with enormous gas
storage tanks. In the centre on the other side was the breeding tank.
Lowe and Safran were standing guard outside.
       As the Doctor stood considering his next move, K9 glided up
behind them, having lost the guard in the maze of corridors.
       'Mission accomplished.'
       'Good dog. Your turn now, Leela. See you back at the
TARDIS.'
       'Good luck, Doctor,' whispered Leela. 'You know, I still think
we should have done what I said!'
       'What was that?'
       'Blown it up!' said Leela unrepentantly. She sprinted across the
open space.
       Safran reacted instantly, raising his blaster and firing after her.
But Leela had already disappeared down another corridor, and Safran
ran off in pursuit.
       Only Lowe was left on guard.
       'It's up to us now, K9,' whispered the Doctor. 'This may not be
easy.'
       'Concern is not necessary. I am an automaton.' Without waiting
for the Doctor's command, K9 glided forward to draw Lowe's fire.
       Lowe fired and missed. K9 fired back, but his powers were
failing now and his aim was poor. Lowe fired again, and K9 spun
round in a circle, shot blindly forwards, thudded against the side of
the tank, close to the door, and stopped there, motionless.
       Lowe raised his blaster to finish him off—then saw the Doctor
at the tank, vacuum box in one hand, struggling to open the hatch
door.
       Lowe fired at once—and a freak shot blasted the vacuum box
from the Doctor's hands. It flew open with the impact and the
precious serum leaked slowly across the floor.
       The Doctor stood quite still, shoulders slumped in defeat.
       Lowe came up to him, covering him with his blaster. 'Your
futile attempt has failed, as we knew it would. Now you will join the
Nucleus.' With his free hand, Lowe reached for the breeding-tank
door.
       'Well, I'd rather not do that, actually,' said the Doctor mildly.
       Lowe raised his blaster. 'You have no choice!' He flung open
the hatch door. A fierce, whining, buzzing sound filled the air.
       The Doctor peered inside. Many of the eggs had broken open
by now, and the creatures inside were stirring, waving transparent
wings in a blur of speed...
       'Oh look, they appear to be hatching! ' said the Doctor
pleasantly. 'Are congratulations in order?'
       'You will join the Swarm,' howled Lowe. 'To be consumed! To
become part of our Purpose!' With a wave of his blaster, he motioned
the Doctor towards the open hatch.
       In order to reach the hatch Lowe had moved past K9, who was
now directly behind him, apparently inert. But not quite. K9's eye
screen lit up, dimly, and his antennae raised. His blaster-nozzle tilted
upwards, and using the last vestige of power in his storage batteries,
K9 blasted away at Lowe, firing until his power was exhausted. With
a choking scream, Lowe staggered and collapsed, falling dead at the
Doctor's feet.
       'Well done, K9, well done!' breathed the Doctor. He ran to
slam the tank door shut. 'Come on, K9, let's get out of here while
there's still time. They'll burst out in a minute...'
       'I cannot, Doctor. All reserves finished,' whispered K9.
       'Come on,' said the Doctor. Grabbing K9 by a handy antenna
he began towing him.
     From inside the breeding tank came the fierce gurgling voice of
the Nucleus. 'Come hack, Doctor, come back. We need you!' The
Doctor shuddered, and dragged K9 away.

       In a patch of shadow Lcela waited, motionless, knife in hand.
       Safran came cautiously down the corridor. Leela stayed
completely still, let hire pass her—and then sprang, bearing him to
the ground. Her knife rose and fell. Safran gave a brief choking
gurgle and went limp.
       Leela wiped her knife on the body and straightened up, just as
the Doctor towed K9 round the corner.
       'Enjoying yourself?' asked the Doctor.
       'What about the Nucleus, Doctor? Did you kill it?'
       'No. I lost the antibodies! '
       'Never mind, Doctor,' said Leela cheerfully, 'I've found the
answer—knife them in the neck!
       'Can you do that to a thousand? A thousand thou-sand? You
haven't seen what's hatching in that tank!' 'What are we going to do?'
       'I think I've got an idea. Take K9 back to the TARDIS, he's out
of juice!.'
       'But Doctor...'
       'Move, Leela!'
       Leela shrugged, and began towing K9 away. The Doctor
snatched up the fallen Lowe's blaster and began running back
towards the breeding tank.
       There was just one possible chance—and strangely enough, it
had been Leela's idea all along...
                                12
                             Inferno
       The buzzing sound was fiercer, louder now when the Doctor
reached the storage area. He paused for a moment, looking round him
at the looming rows of tanks. 'This one, I think,' he muttered. He spun
a wheel and there was a hiss of escaping gas. The Doctor went to a
tank on the other side of the one that held the Swarm. Here, too, he
opened a locking valve. The gas hissed out...
       The Doctor ran to the hatch on the central tank, and wedged the
blaster into an angle of the iron frame which supported it at the foot.
Fumbling in his pocket he produced a little ball of fishing line. He
unrolled it, fastened one end to the blaster trigger, the other to the
handle of the hatch. A massive thudding came from inside the tank,
and the Doctor peered through the little window. The Nucleus,
swollen now to enormous size, was lurching towards him through the
bodies of the hatching swarm. They looked like huge, malevolent
dragonflies--and more and more of them were hatching every second.
       'Is that you, Time Lord?' roared the Nucleus.
       The Doctor's fingers were busily checking the knots in the
twine. 'Well, as far as I know, there's no one else except you and me
here, so it must be me!' he babbled nonsensically.
       'You are finished, Doctor!'
       'Not quite,' yelled the Doctor cheerfully. He tied a final knot
and checked that the blaster was securely wedged and pointing in the
right direction.
       'There is no escape for you now,' gloated the Nucleus. 'You are
destined to become part of the Purpose...'
       The Doctor stepped back. 'Well,' he said thoughtfully, 'that
depends how long it's going to take you to get out of there!'
       'Fool! ' screamed the Nucleus. 'Do you think a metal barrier can
hope to contain the Swarm?'
       But the Doctor was already tearing back towards the TARDIS.
       Tentacles flailing, bulbous black eyes glaring with maniacal
rage, the Nucleus hurled its enormous bulk against the inside of the
hatchway door. The heavy metal began to bulge outwards.
       Behind the maddened Nucleus, the fierce buzzing of the
Swarm rose to a pitch of fury.
       The Doctor shot into Lowe's office to find Leela and K9
waiting by the TARDIS door. Fishing the key from around his neck
the Doctor opened the door and vanished inside.
       'Wait, Doctor!' yelled Leela, and began heaving K9 over the
threshold. No sooner were they inside than the door slammed behind
them.
       The Doctor was already busy at the controls. the central
column began its rise and fall, the TARDIS was in flight.
       'Why did you not wait for us?' demanded Leela crossly. 'What's
the hurry?'
       The Doctor leaned back against the TARDIS console, too out
of breath to explain the desperate need for haste. 'You'll see, Leela.
You'll see! ' He turned on the scanner.

      With a final tremendous heave, the Nucleus burst open the
hatchway door. The string round the blaster trigger tightened and the
blaster fired—straight into the methane storage tank opposite. There
was a ferocious roar, and a searing pillar of fire sprang from the tank.
As the Nucleus lurched from the tank, the swirling gases around it
exploded into flame.
      With a last gurgling scream. the Nucleus and all its brood
vanished, consumed in the roaring sea of fire...

      Hovering in space at a safe distance, the Doctor and Leela
watched the explosion on the TARDIS scanner screen. It was an
incredible sight. First the storage station itself sent out a flowering
rose of flame. The flames grew and grew until the entire satellite was
ablaze, a roaring ball of fire against the blackness of space.
      The Doctor chuckled and rubbed his hands, as if warming them
against the blaze.
      'Is it gone?' asked Lecla, awestruck.
       'Yes!' said the Doctor exultantly.
       'All of it?'
       'Yes! Methane atmosphere, you see. Mix well with oxygen, fire
off a blaster and run!'
       The Doctor leaned down to the recovering K9. 'That was a
good idea of mine to blow it up, eh, K9?'
       'Affirmative,' said K9 faintly.
       'What do you mean, a good idea of yours?' said Leela
indignantly. 'That was my ideal '
       'What was?'
       'To blow it up!'
       'Well, then you should be feeling very happy,' said the Doctor,
quite unabashed.
       'Yes, I am...' said Leela, smiling. Then her face became serious.
'I suppose we'd better return K9 to Professor Marius. I mean, he isn't
ours—is he?'

       Things were almost back to normal in the reception area at the
Foundation. The icily efficient receptionist sat enthroned behind her
desk, ready to book in new arrivals. Lofty consultants strode through
the white corridors in solitary majesty, while little groups of nurses
and students hurried by. And the Doctor and Leela stood by the open
door of the TARDIS, about to say good-bye to Professor Marius and
the faithful K9—who was now restored to full vigour, his storage
cells recharged.
       Everyone was a little sad at the parting. Marius shook the
Doctor warmly by the hand. 'Good-bye, Doctor. And thank you for
everything you've done for us! '
       'It was a pleasure, Professor. And we mustn't forget K9. Do
you know, without K9's help, I think we'd all be part of the Swarm by
now...'
       Leela nodded. 'We'd never have managed without him—her—
it! Sorry, K9.'
       'Apologies are not necessary.' Leela bent down and patted him,
and K9 said, 'Thank you—Mistress.'
       Marius laughed. 'K9 seems to have taken to you.'
       Leela nodded without saying anything.
       Marius looked from her to the Doctor and came to a decision.
He cleared his throat. 'Harrum, well, actually...'
       'What is it, Professor?'
       'Well, actually I have to return to Earth shortly, and you could
do me a great favour. Do you think you could possibly—'
       Excitedly Leela finished his sentence. 'Take K9 with us?'
       'Yes!' beamed Marius.
       Leela was ecstatic. 'Please, Doctor, please, please, let's take
him!
       Leela looked beseechingly at the Doctor. Before he could say
yes or no, K9 shot through the open door of the TARDIS like a dog
returning to his kennel.
       Marius smiled. 'I'm afraid K9 seems to have made up his own
mind.'
       Leela dashed into the TARDIS after K9, the Doctor waved
good-bye and followed her and the TARDIS door closed. There was
a wheeling, groaning sound, and it faded away.
       A little sadly, Marius watched it go. Then he brightened. 'Oh,
well, I only hope K9 is TARDIS trained!' Chuckling at his own little
joke. Professor Marius went on his way. It was nice to think that his
old friend was in such good hands...