'Really. I mean, am I criticising you because you'd rather stay here than help look for Nyssa?'

That did it. She turned and went out through the doorway.

Turlough watched for a moment in case Tegan changed her mind, but he wasn't expecting it. Of the three, she was the easiest to manipulate. All he needed to do was to annoy her a little, and she'd jump off impulsively in whatever direction he wanted. He reached into his pocket and brought out the contact cube.

Although he couldn't say so, he blamed his controller for his earlier failure. There had to be a better way of bringing the Doctor down than by striking at his technology; that, after all, was the Doctor's strength. The cube started to glow.

'They've left me alone,' Turlough said as soon as contact was established. 'What can I do?'

' Nothing. Destroying the TARDIS is nothing if the Doctor Nothing. Destroying the TARDIS is nothing if the Doctor lives. lives. ' '

'He's gone.'

' Then follow and kill him. Find a way. Then follow and kill him. Find a way. ' '

Tegan hadn't even gone out of sight of the door when Turlough stepped down into the corridor. It wasn't going to be as simple as it had seemed at first; the corridor branched and divided further down, and the monotony of its appearance was disorienting. She heard her name being called, and she turned back to see what he wanted.

He was walking towards her, and she saw with a start of fear that the door was closing itself behind him.

No doubt it would open again when someone approached it, and if there was any problem in tracking it down there was always Nyssa's book that they could use as a marker, but Tegan still felt as if a cell door had been slammed on her.

But the big surprise was Turlough. He was looking sheepish. He was embarra.s.sed embarra.s.sed.

'Sorry,' he said, 'That must have looked really selfish. I couldn't let you come out here alone.'

It was certainly a change of heart, but Tegan wasn't about to take any bets on how long it might last. When she turned around to lead the way, there was that familiar uncomfortable feeling between her shoulders again.

In fact, she'd been on the point of turning back. It no longer seemed like a good idea to try to catch up with the Doctor, and it was only the thought of Turlough waiting and smirking at her lack of resolve that had caused her to hesitate, but now that he was with her and tagging along, she felt even less able to give up the notion.

So they followed the way laid down by the book, as the Doctor had done, pressing deeper into the unknown craft and walking in what they hoped were his footsteps. They paused only once, when the steady engine sounds from under the decks changed and became less intense. By then they were already some distance away from their starting point; there was no way that they might have seen their link to the TARDIS slowly fading out and leaving a blank section of corridor wall.

The Doctor was either staying well ahead of them or else he'd turned off somewhere. Tegan and Turlough moved as fast as they dared without making too much noise, staying with the main line of the corridor; this way they stood the least chance of getting lost, because they'd be able to trace a straight line back to their starting-point.

They met n.o.body. The place even had an empty feel about it, helped along by the low-level lights. For Tegan it was like an engine yard at midnight, and the only life was that which throbbed through the decks under their feet. Even so, this didn't make her any less uneasy lights of any kind, even at the lowest level, must have been provided for someone to see by. There were sliding doors at regular intervals down one side of the main corridor, but none was open.

Thanks for that, at least, Tegan thought as they pressed on. Tegan thought as they pressed on.

'Was that her?' Turlough said suddenly, and Tegan realised that she'd been letting her attention wander.

'What?' she said, but Turlough signed for her to be quiet.

They listened for nearly a minute, and finally it came again: what Tegan had a.s.sumed to be the far-off moaning of air through the craft's recirculation system was augmented by another, more distinctive sound. It was something very like a human cry.

'Well?' Turlough said.

Tegan listened again, but the sound wasn't repeated. 'I don't know,' she said, 'I suppose it could have been...'

But Turlough was already convinced. He even seemed to be sure of the direction, down a tunnel that intersected with the main corridor only a little way ahead. 'Come on,' he said, 'we'll catch up with the Doctor on the way.'

'Wait a minute! We could get lost!'

'All taken care of,' Turlough said, and he held something out under the nearest of the dim lights.

Tegan took a closer look and saw that it was the abacus.

Turlough took hold of one of the crosswires and sprung it loose from the frame. The beads ran from it easily into his hand, and he crouched. 'We'll leave a trail,' he explained, and he took one of the beads and set it in one of the cut-out squares of the floor grating.

It sat neatly, too small to roll out and too big to fall through. 'All we'll have to do is follow the beads home.'

Tegan couldn't help being impressed. 'Don't miss a trick, do you?' she said.

d.a.m.n it if Turlough didn't come close to actually blushing. 'I look after myself,' he said.

Then both of them heard it, and this time there was no mistaking what it was: a girl's voice, far-off and filled with anguish. Even if Turlough hadn't already come up with a sure method of finding their way back, Tegan would probably have been unable to resist the summons. It was clear evidence that Nyssa was alive and hurt, and for Tegan there was no other explanation.

Leaving Turlough to take care of their trail, she was already heading down the tunnel.

Whatever was making the sound, Nyssa could hear it too.

It came from somewhere overhead. She crouched in the darkness below the metal stairway of the lower deck with her eyes shut, waiting for it to stop. Some of the dizziness was going but there was still the nausea whenever she tried to move, and any sound was like needles in her ears. She didn't know where she was, or how far she'd run; all that she could remember was the advancing edge of the field of instability as it devoured the room around her, and then the blinding pain and the Doctor's voice urging her to keep moving. Well, she'd kept moving even though her vision had been distorted worse than the worst of bad dreams and her head had been pounding with a dull, regular beat.

She'd kept on until a measure of conscious control had returned and she'd found herself half-way down the stairs to the lower deck, clutching the rail and on the point of pitching forward.

It'll pa.s.s, she'd told herself desperately, wanting nothing more than to let herself down slowly and let the bad feelings ebb away, She made it to the bottom of the stairs, where her legs almost gave out. It was then that she'd turned and seen the shadowed area underneath, and she'd crawled into the darkness much as a beaten fox might crawl into its hole. she'd told herself desperately, wanting nothing more than to let herself down slowly and let the bad feelings ebb away, She made it to the bottom of the stairs, where her legs almost gave out. It was then that she'd turned and seen the shadowed area underneath, and she'd crawled into the darkness much as a beaten fox might crawl into its hole.

The wailing had started then. Please, Please, someone seemed to be calling, someone seemed to be calling, help me help me. Even though there were no clear words, the message was plain. It was more than Nyssa could bear. After a few moments she covered her ears and did her best to sit it out.

As she rested, she started to feel better. The improvement was only relative, but at least the nausea began to subside. After a while she took her hands away from her ears and opened her eyes; even the lights no longer hurt. In a minute or so, she promised herself, she'd try to stand. As long as that far-off agony didn't start up again, Nyssa felt that she could face whatever she'd got into.

It was as she was standing that she heard a light footfall on the stairs above.

Nyssa froze, and waited. Whatever was coming down towards her had hesitated, too, but after a moment it came on. She could see its shadow through the open construction of the stairway, and hear its weight on the metal as it descended with stealth. She held her breath.

No details, just a dark shape. It came down to deck level and turned to step out into the light. Even though she'd been determined to stand quite still there was always the chance that it wouldn't see her, and pa.s.s on by Nyssa couldn't help taking half a pace back into the greater safety of the darkness.

The wall behind her was closer than she'd thought.

She came up against it with an almost inaudible b.u.mp... it was almost nothing, but it was enough to be heard.

'Nyssa?' the Doctor said. He was standing at the bottom of the stairway, one hand on the rail, peering uncertainly into the shadows.

For a moment she was sufficiently overcome to hug him, and he was sufficiently relieved to let her. He said, 'Where did you think you were going?'

'I had no idea,' Nyssa said, finally stepping back.

She could even stand without swaying, now. 'I got all scrambled up, and I didn't know where I was going. I was just about to start looking for the way back. Where are we?'

The Doctor looked around. 'My guess is that it's some old pa.s.senger liner.'

'But where are the pa.s.sengers?'

'I don't know. Let's get back.'

Tegan and Turlough had been going wrong for more than half the distance that they'd covered, but they had no way of knowing it. Tegan's preoccupation had been with speed keep going and they'd soon overtake the Doctor and she stayed with the idea much longer than was practical. It was because of this that she'd missed the simple clue that had taken the Doctor off down a side-branch some distance back and eventually to the lower deck where Nyssa had been hiding: the mark of Nyssa's hand, lightly printed into the dust and grime of the corridor wall as she'd reached out to support herself in turning the corner.

But now Tegan had a new preoccupation, which was to track down the source of the sound that they'd heard. In her own mind she was already convinced that it was Nyssa, and a Nyssa in severe distress at that.

Every step closer that she took increased her conviction. Turlough followed, marking their trail and doing his best to keep up.

Eventually, the inevitable happened. 'We're out of beads,' he called to Tegan.

Tegan stopped and looked back. 'But we're almost there,' she said. 'I'm sure of it.'

Turlough shrugged, and showed her the empty frame. Perhaps they could break it up and use the pieces to extend the trail a little, but the difference that it could make would be negligible.

There wasn't a choice. They'd seen enough of the complex of curves and turns that made up the several decks of the liner to know that, without some system of marking the way, they'd have only the slimmest chance of finding their way back. Tegan simply couldn't argue.

'All right,' she said reluctantly, 'we'll head back and see if we can meet up with the Doctor. But leave the trail so we can follow it again.'

Now it was Turlough's turn to lead. He left the frame against one wall as a sign of the trail's end, and they went back to the first intersection of the route back to the TARDIS. And here Turlough stopped.

Tegan looked at him; he was scanning the floor, confused, and she felt an immediate tremor of apprehension somewhere deep inside. 'What's the matter?' she said.

'It's gone.'

'What?'

Turlough pointed. 'The last of the beads. It was there.'

Tegan looked around; two other branch corridors joined close by. 'It must be one of the other sections, then,' she said, but even before she'd finished Turlough was shaking his head. There was no way he could expect to remember their entire route, but he was sure of the very last turning they'd made.

He wasn't quite so sure about the next intersection, but he set out to check with Tegan only a little way behind. She was thinking that perhaps the bead had dropped through the grating. They couldn't all be a regular size, and besides, there was no other explanation from all that they'd seen, they were alone on a deserted ship. She and Turlough had come far enough for her to be sure that, if there had been anyone around, they'd at least have seen a sign of it.

And if there was n.o.body to disturb the beads, it therefore didn't make sense that the beads should be disturbed...

Turlough reached the corner, and stopped abruptly. There was no more than a fraction of a second's reaction time in which he stood with amazement on his face, and then he was hustling Tegan over to the corridor wall and motioning urgently for her to be quiet.

She tried to pantomime a look of enquiry. He stepped aside so that she could take a cautious peek around the corner. His hand was on her arm, ready to pull her back if he saw unexpected danger.

There was some kind of robot, and it was picking up their beads.

It was small and battered, and no attempt had been made to mimic a humanoid shape. It was an obvious work-horse machine, a drone. From the front, its bodysh.e.l.l presented an octagonal profile with diode lights and indicator panels on the forward section.

Above this, in lieu of a head, was a camera housing raised on a curved gooseneck stalk. It looked like the flattened head of a snake as it scanned from side to side, searching across the flooring for anything else to collect. Folded flat against the sh.e.l.l were anglepoise arm mechanisms, each tipped with an evil-looking blade or drill facing forward like weapons at the ready.

Two of these both pincers had swung out for use, one to pick up the beads and the other to hold the growing collection in a semi-transparent bag.

Satisfied that there was nothing else to be found, the drone straightened. It had probably been programmed to keep the corridors clear of any obstruction, large or small. If it had any defence function in addition to simple maintenance, neither Tegan nor Turlough wanted to find out the hard way.

They watched as it turned, centred itself on its gyros, and moved off in the opposite direction. Some way down the corridor it stopped, turned, and set off again, and eventually disappeared out of sight.

And it took all their chances with it, rattling together in a semi-transparent bag.

Their names were Olvir and Kari, and they were raiders. Their entry into the liner was no less spectacular or unusual than that of the TARDIS party, and it was carried off with considerably more noise and damage.

The sequence had been well rehea.r.s.ed, in simulation and on countless other real-life missions.

The limited spread of the thermic charges attached on the outside instantly vapourised a ring of metal large enough for them to pa.s.s through. A high wind blew down the corridor section as air drained out through the hole and the ventilator pumps went into overload trying to replace it, and dust and debris whirled around in the vortex before the gap as the two suited figures entered.

Kari was first because she had the experience. She came through with her burner ready to fire and expecting trouble, bracing herself against the tug of the air-loss and scanning around in an even sweep.

Olvir was at her back in a moment, and as the strong winds died they stood and kept both main approaches covered.

They were wearing lightweight a.s.sault gear, enough for a few minutes' resistance to vacuum without slowing them down. The close-fitting suits and the smooth pressure-helmets gave them an intimidating appearance which, after the shock of the initial entry, was usually enough to overcome any resistance.

a.s.suming, that was, that any kind of resistance was presented; the lack of resistance was the first thing on the liner that didn't coincide with what they'd been expecting.

The outward rush of air finally stopped. Both raiders carried hand-radios clipped alongside the spare power-packs on their belts, but a.s.sault procedure required radio silence until primary reconnaissance had been carried out. They restricted themselves instead to the low-power helmet communication that couldn't be picked up outside a circle of a few metres.

'Check the air-seal,' Kari said, and she kept watch in both directions as Olvir went back to their entry point.

The hole was now plugged with what appeared to be solidified foam. Olvir spread his fingers and pushed against it, but his gloved hand barely made a dent. A few minutes longer, and the foam would have set as hard as the metal around it.

He signalled to Kari that there was no problem. A last check in both directions, and then with a jerk of her burner she indicated for him to follow as she set off down the corridor.

They'd spent six of the last twelve hours in deep hypnosis, memorising every turn of the route ahead as it was shown in plans that the Chief had bought under a false name for the servicing agents not that this particular model appeared to have seen a service bay in more than its safe quota of runs, which was a second worrying factor.

The plan was to fight their way from the access point to the bridge, where they were to take prisoners and over-ride the airlock seals so that the main force of the raiding party could enter. It was for this that they'd fixed in their minds every sc.r.a.p of cover, every firing angle, every short-cut and potential source of a hidden enemy. But this this... this wasn't right.

The light was bad, and the corridor was grimy.

There were no guards and no defensive devices. Ever suspicious, Kari wondered if it was some kind of original approach designed to get their defences down so they could be hit without expecting it; but as they came into the last part of the run leading to the liner's control room and they'd still seen no signs of life, she was starting to discount the theory.