'All right... what do we do?'

'We go to the place where you lost track of the thing you chased. If there is any way out it will be there.'

'Doctor,' said the android Susan, standing before the nervous crowd of NC2s. 'We can't leave these people here. If there's a chance we must try to save them too.'

For a moment Ian thought the Doctor was going to argue.

Then he inclined his head slightly.

'You are right. They deserve the same chance as we have.'

He turned to Lant. 'Take Mr Curton and Miss Shardri with you, drive into the city and find additional transport.

Commandeer some of those dummy cars if you must, but bring back enough vehicles to carry these people. Quickly.'

The three climbed into Lant's car and sped off towards the city. They seemed relieved to have a job to do; to distract their thoughts from the destruction of the Ship. The Doctor addressed the NC2s.

'Divide up the provisions into bundles you can easily carry. If you can find more clothes put them on. Use anything in the camp you need. This... young woman will help you.'

Galvanised by the Doctor's words the NC2s began to move with a sense of purpose for the first time. They laid out blankets and plastic bedding-sheets and began piling goods from the storeroom on to them.

Suddenly Ian felt the ground tremble, and staggered slightly. A few of the children began crying again.

'Earth tremor,' said the Doctor. 'Shock waves generated by minor fragments from the moon's break-up striking the equatorial zone. We can expect worse to come.'

Lant and the others returned after only fifteen minutes with two low-slung six-wheeled light trucks.

'They were in a factory yard,' Lant explained. 'Power cells still half-charged.'

Two older NC2s who could drive the vehicles were found and the rest climbed on board. Once again Nyra rode in the back of Curton's car to watch Vendam, who was showing signs of regaining consciousness. The Susan android climbed in with her, while Ian and the Doctor rode with Lant. The little convoy swung about and drove out of the camp.

Over the tops of the distant towers they could see fresh columns of smoke rising from spreading fires to join the central pall, shrouding everything in a sudden twilight. Lant switched on his headlights as they sped along the streets that skirted the edge of the Outer Zone.

Out across the levelled land a wall-turret launcher suddenly belched fire as a salvo of missiles tore away into the sky.

'The meteor defences must be on automatic,' Lant explained, adding grimly: 'Let's hope they don't have anything too big to handle for the next hour.' He glanced at the Doctor, confusion distorting his normally composed features. 'You said the Ship couldn't fly. Did you really mean it? How do you know?'

'Do remember, young man, that I have considerable knowledge of nuclear drive systems and s.p.a.cecraft design. It was for those very skills that I was asked to check over the Ship's plans. But Professor Jarrasen tried to keep my attention focused exclusively on the landing module. That was what first reinforced my suspicions and the reason why I insisted on touring the Ship personally. It allowed me to estimate its structural weight, engine thrust and payload. I could soon tell it did not have enough power to take off.'

'But why? And who was attacking it... the NC2s? Did they destroy it by accident?'

'I do not know who was attacking the Ship, but I'm afraid the explosion might not have been an accident. It is consistent with the existence of the secret tunnel.'

Lant looked dazed. 'What tunnel?'

'The one that runs under the city towards the mountains...

at least, so the alignment suggests.'

'Alignment from where?'

'From the Ship through the point where you lost your mystery quarry.'

'What do you mean?'

'I'm sorry, Captain, you do not yet appreciate how completely you have been deceived. Remember my questioning the necessity of such a deep blast pit beneath the Ship? I imagine the tunnel was dug under cover of its excavation. It would have connected with a lift shaft concealed in one of those absurdly ma.s.sive supporting legs, opening through the base of the nacelle so nothing was visible above ground. The system ran up through the skin of the outer hull to the Lander. When I toured the control cabin I noticed one of its bulkheads was deeper than was shown on the plans.'

Ian saw Lant was clutching the steering wheel so tightly his knuckles were white. 'But why? What was the system for?'

'To secretly move people and supplies out of the Ship after those zealous faction guards at the perimeter gate had checked them in, naturally. They would then travel to a secret destination that served a purpose for which a manual labour force was also apparently required, hence the kidnapping of escaped NC2s in the Outer Zone. That was what first made me suspicious of an inst.i.tutional conspiracy. Camp security was really too lax for it to be accidental.'

Before Lant could ask any more questions, they were pulling into the dead-end yard where they had lost their mystery quarry the previous evening. The Doctor climbed out and began gesturing to the occupants of the other cars, including the NC2s, to disembark.

'Listen to me carefully. Somewhere in this yard we believe there is a concealed gateway. No doubt it is normally operated by remote control, but undoubtedly there is a manual switch for emergencies. We must find it if we are to survive. Examine every surface, check every brick in the walls. Press or twist anything that seems loose.

In seconds the yard was full of people tapping and sc.r.a.ping the walls and ground.

As Ian prodded a course of bricks, cinders began falling from the smoky overcast sky. The city was burning. Of course, none of this would matter in a few hours, but it reminded him that the TARDIS was lost and with it any hope of returning to their own time. But if there was a chance Barbara and the real Susan had been taken down the Doctor's hypothetical tunnel, then that was all that mattered. As long as they were together they would somehow win through.

The ground trembled again, the result of distant meteor impacts presumably. At least they might be underground before the sound reached them. But how long would the tunnel, if they could find it, remain intact under such conditions?

'Over here!' one of the NC2 women shouted.

Halfway along the left-hand wall she had found a false brick which hinged open to reveal a single large b.u.t.ton.

Without hesitation the Doctor pressed it.

The wall at the end of the yard slid aside to reveal a dark opening beyond.

'Everybody back in the vehicles,' the Doctor commanded.

'There's room enough for all at once.'

They drove forward into a featureless chamber. The wall automatically slid closed behind them. There was a faint whirr of motors and a sudden sinking sensation. The sides of a shaft rose up past the windows of the vehicles. In seconds the downwards motion ceased once more. They were in a recessed bay opening off a long tunnel with smoothly cut walls. Lant led the way forward, turning his car away from the centre of the city. The tunnel stretched before them in a straight line to the limit of the car's headlights.

As they accelerated, with the other vehicles following close behind them, Lant asked: 'Any idea what we'll find at the other end?'

'I have my suspicions,' the Doctor said. 'But princ.i.p.ally I expect to find somebody I have only seen over a vision screen, yet who should by all rights have been at the Ship yesterday.'

'You mean Jarrasen?'

'Yes. And the place where we find him may also hold our last chance of survival.'

Chapter Thirty-Two.

Reunion Barbara, lying on her bunk in the barracks cave, winced as Susan dabbed her head with a damp towel.

'How long was I unconscious?' she asked faintly.

'About two hours,' Susan said. 'The guards got control and drove us back in here. We had to carry you.'

Barbara grimaced. 'Did I really behave that strangely?'

Susan nodded. 'Yes. I was terribly worried. But you seem to be over it now. Maybe because of the knock the guard gave you.'

'I don't know what came over me. I simply knew I had to get back to the city and the Ship. It was like a compulsion.'

Susan shrugged. 'Well, it did let me to do something useful without anybody noticing. I hope it worked.'

'What?'

'You'll see. But I don't think we've got much time. Can you stand?'

Barbara swung her legs over the side of the bunk and sat up gingerly. With Susan's help she stood, swaying slightly.

'The guards aren't patrolling as usual,' Susan said. 'I think we can break down the inner barred doors without being heard.'

'But the others are solid.'

Susan simply smiled enigmatically and led her to the double part.i.tion that separated the men's and women's dormitories. Plaxander Vendam was pressed against the bars on his side looking at them across the narrow aisle between them. There was considerable activity going on behind him.

'Is she all right?' he asked. Barbara thought he sounded genuinely concerned. Quite a change from the brash young man they had met only the day before.

'Yes,' Susan said. 'How's it going?'

'Almost ready.'

'What are they doing?' Barbara asked.

'Making long levers out of the bed stanchions to use on the door bars.'

'But they're only light metal, aren't they? I wouldn't have thought they'd be strong enough.'

'That's what we worked out while you were sleeping.

They're laying three or four sections together and binding them tightly with belts. Then they'll use two or three levers at the same time to bend a single bar.'

Barbara laughed and winced, clutching her head. 'Like Archimedes said about levers: give me a firm place to stand and I will move the Earth.'

Susan smiled. 'Well, more or less. Although, as Grandfather pointed out to him, he hadn't explained what he would use as a fulcrum. Look, I think they're ready.'

The men were hefting their improvised levers. The women crowded about the corner of their section to watch as they inserted the levers through the bars and bent their backs. They heard grunts of effort and began to shout encouragement.

Suddenly there was a loud snap and metallic tw.a.n.g. There was a quick cheer, a few seconds wrestling with the broken bar to twist it out of the way, then Plax wriggled through the gap and stood up triumphantly outside the bars. The other men began to follow after him.

In a couple of minutes they had used the levers to break open the women's dormitory and the female prisoners jostled out to join them.

'We must get through the dining hall so we can reach the door of the equipment cave,' Susan said.

'That's too solid. We'll never break it down with these,'

said one of the men.

'Listen to her!' Plax said with an unexpected ring of command in his voice. 'She knows what she's saying.'

'During the confusion earlier I jammed a piece of metal into the latch slot,' Susan explained. 'Hopefully it won't be properly locked and we can slide it open.'

'You heard that?' Plax asked. 'Right, let's get the next door open.'

They set to work on the door leading to the dining hall.

'What if there are still guards out there?' Barbara wondered.

'The others seem to think they'll all have gone back to the city to get on the Ship,' Susan said, but she was frowning.

'Don't you think so?'

'I'm not sure. We still don't know what this place is for.

Why go to all the trouble of building that channel and embankment, and keeping it so secret? The most important thing on this planet seems to be the Ship so what were they doing here?'

'But Ian and the Doctor and the TARDIS are in the city so we have to get back there,' Barbara said. 'I just hope we can find some transport or else it'll take us a day to walk...' she broke off, feeling the ground tremble under her feet. Several workers glanced round nervously. 'If we've got that long,' she added.

A bar was bent aside. The workers began to squeeze through the gap into the dining hall.

Suddenly Semanov, standing at the back of the group, shouted: 'There's something coming through the air vent... it's gas, it's gas!'