'Why! Because that's when the moon's going to smash us.

Where have you been for the last ten years?'

'Never mind where, Mr Gelvert,' the Doctor snapped.

'Remember our bargain. What brought about this unfortunate state of affairs?'

Still looking at them very strangely, Gelvert said: 'An asteroid knocked it out of its...o...b..t so it came in close to us.

The equatorial regions got hit by meteor storms from the small pieces the asteroid blasted free. The moon went on out into s.p.a.ce again, only not quite so far as before. And its...o...b..t got a little shorter. It goes the opposite way to the way Sarath spins.

Every time it makes a close pa.s.s it loses more speed.

Something about our magnetic field.'

'Of course,' said the Doctor, half to himself. 'Its core must have an unusually high ferrous content. That would slow it down far more rapidly than gravitational forces alone. How large is the moon?'

'Uh, hundred and fifty Ks across, maybe.'

'Too large to destroy or deflect by conventional means,'

the Doctor said. 'Yes, the devastation would be tremendous.

The crust of the planet might be split wide open!'

Ian felt slightly sickened at the thought. 'So what we saw today was just a foretaste of what's to come.'

'It would be like comparing a few tossed pebbles to a landslide that carries away half a mountain,' the Doctor said solemnly. 'This city has evidently been very fortunate, so far.'

'Well away from the worst of it up here in the North,'

Gelvert said. 'Only get a few strikes like today, and the odd tidal wave. Before I got here, I saw...' he faltered, as though fighting against some intolerable memory, then anger took over. 'Doesn't matter what I saw. It won't happen to me like that!'

In the silence that followed Ian said: 'So the wall was built against tidal waves.'

'And the Bronzers,' said Gelvert moodily.

'Who?'

'The Taklarians. When the moon started falling and their lands were smashed they tried to move north. Overran everything until Arkhaven stopped them. That's the last of their battle craft out there on the beach. They wanted to take a ride on the Ship.' He laughed ghoulishly. 'Now all they've got is a pile of sand as a tombstone.'

Gelvert paused as a small powered cart appeared rolling along the path. Its open back was stacked with trays of a.s.sorted small goods. It halted a little way along from them and a man in a bright green coverall got out of the cab. Several NC2s emerged from their shelters and rapidly gathered about the cart, apparently negotiating to buy items from his selection.

'Back in a minute,' said Gelvert, and joined the back of the small crowd. He was the last to be served, and Ian noticed he spoke to the trader for significantly longer than the previous customers. Eventually Gelvert turned away, tucking a few small items into the inner pockets of his long, patched coat.

The trader climbed back into his cart and it trundled silently away.

'Who's that?' Ian asked Gelvert as he rejoined them.

'Lesitor. He's got the franchise to supply a few luxuries to the camp. Keep back a few ration slips and you can buy fresh fruit, sweet bars, a warm coat. Get you anything for a price.

Got an eye for a good deal, has Lesitor. He'll be trading right up to the day the Ship lifts.'

'Yes, the Ship,' said the Doctor. 'Where is it bound?' He quickly held up a hand to forestall another incredulous response from Gelvert. 'I know you cannot believe we need to ask, but tell us anyway.'

'Mirath, of course. Next planet out from us. When the moon started falling, Arkhaven sent an automatic probe rocket there. They found it was colder than Sarath, but it had breathable air and water and even some vegetation.'

The conditions sounded to Ian rather like those Mars had once been a.s.sumed to possess. 'What do you think about going there?'

Gelvert stared at them in frank disbelief. 'You really don't know, do you? Why do you think the people in this place look like they're already in the morgue?'

'Perhaps you would enlighten us,' the Doctor said.

For the second time Gelvert sounded angry and resentful, and a little colour came to his bony cheeks.

'When Arkhaven started building the Ship they designed it to carry their own people and the tools and supplies they'd need on Mirath, plus a bit of s.p.a.ce for special cargo. But that was before the war refugees from the other cities started arriving. Now there's only room for a few extra people with special skills, or those the Elite families want as servants...

slaves more like!

'The rest of us stuck in here,' he jabbed his finger, 'that's you and me, they're just going to leave behind. For a few days after the Ship lifts we'll have the whole city to ourselves. Then the moon'll hit.' Gelvert punched his fist into his palm. 'And the world'll crumble to pieces under our feet!'

Chapter Four.

Underground Barbara slowly recovered consciousness.

It was an effort to force open her eyes. When she did there was nothing but blackness and it took her several blinks to decide that her eyes really were open and that there simply wasn't any light to see by.

She was lying on her back with the taste of grit in her mouth. Her head was pounding and she felt dangerously sick.

Every part of her body seemed to ache but she was alive.

Stay still, she told herself. Get your breath back. Wait until everything stops spinning round.

She remembered the moments before the lift fell.

There had been a swelling roar as an avalanche of concrete filled the hollow sh.e.l.l of the building, smashing into the lattice of bracing struts and snapping them like matchsticks.

Instinctively she had pushed Susan back through the door of the lift, even as its supporting beams shivered and then bowed outwards under the impact of the descending debris. Metal screeched as one set of lift-runners came free of their supporting beams, the sudden shock of separation jerking her off her feet before she could follow Susan. Some automatic safety brake on the remaining runners slowed the lift's fall, but to Barbara it still seemed to plummet like a stone. It struck bottom with enough force to drive the breath from her body, even as debris began to pound its metal frame.

Then there was a blank.

Now she lay in blackness, its silence broken only by the sound of her breathing. As her daze lifted she became aware of a length of ribbon twisted about her hand. It took her a moment to work out what it was. Mustn't lose that, she thought muzzily, and tucked it into the seam pocket of her slacks. Even this simple movement hurt.

At least the lift cage had protected her from being crushed.

What were a few bruises compared to that? But she was still buried under many tons of rubble, somewhere in the lower levels of the tower.

She began to feel panic rising within her but firmly quashed the sensation before it had a chance to take hold.

Losing control of yourself won't do you any good, she thought. Wait until you feel better before trying to do anything.

She diverted herself for a minute or two by planning what she would say to the Doctor when she next saw him. Still, she knew he would do everything he could to find her. Ian and Susan would see to that. Yes, they would all come for her eventually.

But how long would it take?

If only she had a light.

Wait a minute, she thought. Inside the lift cage beside the control panel there had been a tubular object held in place by a spring clip. She hadn't paid it much attention at the time but it could have been a torch. It made sense to leave one there. Now if only she could find it.

Feeling the wave of sickness slowly subsiding she tried to sit up.

'Oww!' she gasped and lay quickly back down again.

She had cracked her head on something no more than two feet above the floor of the lift. Cautiously she reached upwards and felt buckled metal mesh, that had been torn through in places by the broken edges of concrete blocks. It must be the roof of the lift cage. It had been hammered down almost on top of her.

How much weight must it be supporting and how long would it continue to bear the load?

Again she fought down the impulse to panic. This was not the time or place. Later she would let her feelings out, but not now.

She reached out experimentally on either side. Her right hand brushed against crumpled heavy wire mesh. Yes, that must be the side panel of the lift cage. She rolled over, wincing as jagged shards of concrete ground into her, and pulled herself up to it. Now, feel along until you reach the corner post, she told herself. There it is. Now, if this is the front of the cage, the control panel should be up here and the clip should be to the right. Her questing hand ran across twisted mesh until it closed on what she sought. It was still in its place! She pulled it free, fumbled until she found a b.u.t.ton on its side and pressed.

White light flooded the cramped s.p.a.ce. Her gasp of relief was choked back as she saw the entire roof of the cage was bulging downwards to a frightening degree. The tilted and warped floor was already littered with dust and small fragments of stone that had apparently been driven through the many rents in the framework.

Somewhere in the ma.s.s of debris above her stone cracked and metal gave forth a rending tw.a.n.g. A dribble of dust and grit pattered softly on to the lift floor. She looked about desperately. The lift door was wrenched half off its hinges.

Beyond was a crazy jumble of concrete blocks and a twisted length of metal beam. Between them was a narrow aperture framed by the dancing shadows cast by the torch.

Barbara twisted round and kicked at the door, bending it back far enough for her to squeeze through. The lift cage groaned and squealed and the roof sagged lower.

She forced herself through the gap between the twisted mesh panels of the door. The hem of her jumper caught on a snag of wire, pulling her backwards. She tore it free with a frantic jerk, ripping the yarn, and hauled herself clear.

She crawled through an arch formed by two crossed pieces of concrete beam and, at her heels, the cage folded up and was crushed flat. Immediately the arch began to collapse in turn as the pressure from above shifted to fill the new void.

Ignoring sc.r.a.pes and grazes Barbara scrambled frantically along on her hands and knees, trying to hold the torch as she went, slithering into whatever gap next presented itself. All she cared about was getting clear of the settling ma.s.s of wreckage, driven by the horror that any second now it would all give way, trapping her helplessly as it crushed the life from her.

Her hands pressed down on a slab that rocked and then suddenly tilted upright. Before she could stop herself she fell forward headfirst into a black hole, taking a shower of loose rubble with her.

She struck the floor of a shaft running downwards at an angle of about thirty degrees. Its sides were wet and slick with slime and Barbara began to slide. She scrabbled frantically but could not find any grip to slow her descent.

Then the slope of the shaft abruptly flattened and she was shot out into a black void. Even as she screamed in utter terror she struck water with an echoing splash. Coughing and spluttering she surfaced, threshing about wildly for a moment until she found her feet were touching the bottom. She stood upright and found the water only came up to her hips, lapping about them under the impetus of a gentle current.

She was still holding the torch; locked in her clasp by the fear of being lost in the dark once more. She had to steady it with her other hand, and realised she was trembling violently.

Its beam illuminated a ledge rising clear of the water just a few feet from her. Above it a dark wall curved up and over to form the roof of a large tunnel. She waded over to the ledge, hauled herself out of the water and lay there panting.

She felt cold, wet, miserable, bruised and frightened. She pulled her knees up to her chest and allowed herself to cry heartily for a full minute.

When it was done she felt better. She sat up, wiped her eyes, and then took a careful look round at her new surroundings.

The tunnel, perhaps twenty feet across, vanished beyond the range of her torch beam in either direction. From where she sat she could see three openings s.p.a.ced along its sides, identical to the one she had emerged from so dramatically. She guessed she was in part of a storm-drain system. It was not the most pleasant location but she consoled herself with the thought that it could have been a sewer. The air was damp with the smell of mildew but the water seemed relatively clean.

So, what should she do next?

There was certainly no way she could climb back up the shaft she had come down. It might even be dangerous to try with all that wreckage up there. But when the Doctor and Ian and Susan came looking for her they would eventually uncover the upper opening. She would hear the activity and could call up to them.

But how long would that take? If the whole building had collapsed it might be days before they could dig down that far, a.s.suming they could get help from the locals. They might think she was already dead. If she could get herself back up to the surface, then she could spare them a lot of needless anxiety.

Suddenly Barbara pounded the sides of her head with her clenched fists in disgust. 'Self, self self!' she shouted angrily, the words echoing down the tunnel.

She had been so wrapped up in her own plight that she had forgotten that the others might have problems of their own.

Did Susan get dear in time? If there had been another meteor strike on the roadway while Ian and the Doctor were still out there...

She scrambled to her feet as rapidly as her stiffening and bruised muscles would allow. There was no way she could wait pa.s.sively to be rescued. She had to get out as soon as possible.

If she simply followed the direction of the flow of water she would be bound to come to some sort of maintenance access point or to the tunnel's outfall. Then she could make her way back to the others long before they could reach her.

But, just in case, she would leave a sign.

She made her way along the ledge until she reached the point below the shaft she had fallen through. Grimacing, she slid back into the water and felt around with her feet until she found a fist-sized splinter of concrete that had come down with her. She pulled herself back on to the ledge and began sc.r.a.ping at the stonework under the lip of the shaft. In a few minutes she had marked a bold B> in the wall, with the arrow pointing in the direction she intended to travel.

Then, torch shining hopefully ahead of her, Barbara set off down the tunnel.

Chapter Five.

Hospital The autosystem monitoring the new patient's progress beeped urgently, informing senior clinician Nyra Shardri that all was not well.

She left her station in the middle of the intensive care unit and crossed over to recovery tank five. She could have called up the information on her own console, but she liked to get close to her charges. Of course the machines did the actual work, but she felt human contact should be a part of the healing process. Theoretically, she could even take over if the machines and their back-ups failed. She had done well in simulated medical emergencies, but so far she had never been put to the test with a real person. A century ago practically all medical procedures had been performed by humans their primitive machines were there only to a.s.sist them. Now n.o.body in Arkhaven would trust themselves exclusively to a human doctor.

Within the tank a pale-faced young woman dressed in a hospital gown rested on a contoured body pad. Robot arms had already put the usual support and monitoring lines in place. Re-gen pads on her head, chest, left arm and right leg indicated that major injuries were being stimulated into accelerated healing.

The display read: NC2-Susan Foreman. Traumatic shock victim. No ident.i.ty code/registration number. No previous medical history. code/registration number. No previous medical history.