He nudged the Doctor.

The TARDIS. Monitor must have had it brought here before the city was destroyed. If only we had a key!'

'Monitor,' the Doctor called out. 'I see you have my vessel here. Obviously you want to take it to Mirath to study it further. If you take these people with you, I'll tell you its secrets.'

'I will decipher its functions in my own time, Doctor.'

The Doctor bridled indignantly. 'Without my a.s.sistance you will fail even to open the door.'

'You have already outlined the principle behind the design of the key, Doctor. I will replicate it, given time. And I will have plenty of... of...'

Monitor's voice began to falter, its eye ring flickering unsteadily.

Susan and her android twin appeared out of the shadows.

They were walking shoulder to shoulder, holding hands in a firm grip. Behind them came Barbara, Nyra, Plax and his father, who was looking weak but resolute.

'You can't control me, Monitor,' the android Susan said.

'You can't control my mind because I'm not one of your androids and our minds are linked,' said the real Susan.

Monitor's androids tried to turn their guns on the pair but they seemed incapable of aiming properly. They began firing wildly into the air. The prisoners scattered away from their suddenly distracted guards.

'I... will not be controlled again!' Monitor grated.

The two Susans sank to their knees as though fighting some invisible weight bearing down upon them. Their companions were cl.u.s.tering round them protectively, as though adding their wills to the struggle.

'Doctor!' Barbara shouted. 'Turn Monitor off while they've got it trapped!'

Ian half-dragged the Doctor forward towards the terminal, dodging between staggering, confused androids, bullets flying about them. One of the facsimiles reeled into the Doctor, sending him sprawling. Ian tried to wrestle the thing out of their way but he suddenly found himself fighting inhuman strength. Its grip was like iron and it drove him to his knees.

Then he heard Nyra Shardri cry: 'Ben, help us!'

The android carrying the memories of Ben Lant felt the link with Monitor weaken for a second. It heard the voice of the woman who loved the human form it mirrored and felt the battle between Susan's twinned mind and Monitor. It knew what it had done and what it had to do. Steadying its hand for the last time it emptied the magazine of its gun into Monitor's terminal.

The androids in the hangar jerked as one and collapsed.

The screens above the bullet-ridden terminal flickered and went dark. Sparks crackled and smoke began to rise from under the control boards.

'He's transferring into the Lander!' Susan called out faintly. 'We can't hold him any more!'

Ian hauled the Doctor to his feet and helped him over to the terminal. The Doctor's hands flashed over the b.u.t.tons even as he coughed in the rising smoke. But after a few seconds he staggered backwards.

'It's no use. The input controls are severed. The transfer process is operating and I can't override it!'

'Then Monitor will take over the Lander!'

There was a screech of tyres and Curton's truck appeared, weaving between the running people, crates and machinery scattered about the hangar floor.

Ian waved at him and pointed at the terminal even as he pulled the Doctor out of the way. 'Smash it!'

Curton made a sharp turn, the engine whined and his truck seemed to leap forward. There was a crash of rending metal and a shower of sparks, as panels and fragments of circuitry flew through the air. The truck ploughed through the terminal, grazed a wall and came to a shuddering halt.

The echoes died away and for a moment the hangar was totally silent.

The truck door opened and Curton hauled himself out a little shakily. His nose was bleeding. He looked back at his handiwork and then at Ian.

'That what you wanted?' he said.

Ian nodded. 'That was exactly what I wanted.'

Cautiously people began to emerge from around the hangar where they had taken shelter.

Susan and her twin were being helped to their feet. All the other androids lay motionless where they had fallen.

'Are you all right?' Ian asked the Susan android.

'Monitor wiped their memories to shut them down, but my link with Susan blocked the command.' It smiled. 'I'm fine.'

Nyra was bending over the body of Lam. It was absolutely still and quite dead, the face almost calm in repose. Nyra began sobbing quietly.

There was a feeble moan from above. Ian looked up to see one of the flight crewmen, blood on the side of his uniform, clinging to the top of the Lander's access ladder. A wisp of smoke was coming from the open hatch above him.

'Fire... in the control room!' the man gasped.

There was a rush for the ladder. It took only minutes to extinguish the smouldering electrical circuits under the control boards, but by then it was too late. The Doctor surveyed the fused and charred remains and shook his head grimly.

'The piloting controls are ruined. It would take weeks to repair them, a.s.suming the proper replacements were available.

Was it an accident or a deliberate overload: a final spiteful act by Monitor. I wonder? How very human that would be.'

'Whichever way, we're done for, aren't we?' Ian asked.

The two Susans, Vendam, Plax and Curton looked equally dismayed. Barbara was frowning as though puzzled. She opened her mouth to speak when Draad, standing grey-faced at the Doctor's side, said: 'No, this can't be the end! Not after everything we've gone through!' His eyes flashed in desperation. 'What about Monitor's mainframe? It has parallel control circuits. Yes, the autopilot programme could still fly the Lander through that!'

He led the way in a stiff run back through the bulkheads which had been modified from the decks of the original design. Monitor's mainframe unit appeared intact. The Doctor tapped out a test pattern on the keyboard. The power lights burned but the screens remained blank.

'All the operating programmes have been purged from the system, including the back-ups,' the Doctor said. 'There are no autopilot functions to interpret the commands. We can launch this vessel... but there will be no way of landing it on Mirath.'

Chapter Thirty-Five.

At World's End Even as they took in the awful implication of the Doctor's announcement, Draad's face contorted with pain. He clutched at his chest and his legs seemed to give way. Ian caught him as he fell and lowered him gently to the deck.

Susan ran to the hatch and called out: 'Nyra... it's Mayor Draad. He's collapsed.'

Nyra had remained outside by Lant's body. Now she quickly wiped away her tears and climbed the ladder to the control room, watched intently by those in the crowd who had heard Susan's words. Kneeling beside Draad she unfolded her medical kit.

'Tablets... in pocket,' the mayor gasped.

Nyra found them and read the label, then hastily loaded a cartridge into her spray syringe, pulled Draad's jacket open and injected the cartridge into his chest.

'He needs a proper resuscitation facility,' she said. 'Have they got anything like that here?'

Draad's breath was coming in painfully short gasps. He beckoned feebly to the Doctor and Ian.

'Maybe this is a punishment for doubting the Maker,' he whispered. 'I know what's wrong... always hoped I'd make it through the flight. I did what I thought best... never forget... I just wanted to save as many as I could. Do you understand?'

They nodded. Draad winced again. Promise... you'll get them to Mirath... somehow.'

'I promise,' said the Doctor.

Draad's eyes closed. His back arched, then relaxed. The breath rattled in his throat, then the pain went from his face.

Nyra felt for the pulse in his neck, gave him another injection, then checked again. After a few moments her hand dropped away and she shook her head.

'He's dead.'

After a moment Curton said: 'That was decent of you, Doctor, but you know there's absolutely no way you can keep that promise.'

The android Susan broke the ensuing silence. 'Perhaps I can fly the Lander.' They stared at her and she continued hurriedly: 'If Monitor brought equipment here for our maintenance, then there should be an interface link that will allow me to connect my brain directly to this mainframe. I could control the ship through that.'

The Doctor looked at her with dawning hope, then shook his head. 'Even if you can make the link, there are no programmes to interpret your commands or tell you how to fly it.'

The android glanced at Susan. 'Remember the applied science moon camp? We flew simple ships like this. I'll have the printed flight plan to follow, I can study the systems on the way and I'll remember everything perfectly. That's one advantage of being a machine.'

'She's right,' said Susan. 'She can do it, Grandfather.'

The Doctor looked at the android gravely. 'But even if you succeed, the colony may not be able to maintain your mechanical systems. Eventually you will...' He broke off, and looked genuinely sorrowful,'... break down. You'll die.'

'I know. But I want to do this for myself, not as a copy of Susan. I'll just have to make the most of the time I've got.

Isn't that what people do?'

Slowly the Doctor smiled. 'Yes, that is what people do.'

He turned to Lord Vendam. 'If you have some influence with the crowd outside then use it. They must stay calm while we see if this will work.'

To his credit Vendam did not argue. 'I'll do my best, Doctor.'

With Plax supporting him he walked over to the hatchway and looked down at the crowd gathered below. Former slave workers and guards alike, enmity for the moment forgotten.

'I regret to tell you that Mayor Draad is dead,' he announced.

The crowd looked lost, bewildered, frightened. Draad had governed their lives, for good or ill, for years. There could be no more potent symbol of the death of their old existence.

'But his work continues,' Vendam added forcefully. 'Now move back from the ship... it has to he prepared for launch.

You in the grey uniform: where can we put these bodies...?'

They descended the ladder, Vendam giving orders as he went.

'I'd better check on the wounded,' Nyra said, repacking her medical kit and following them.

'Mr Curton,' the Doctor said. 'I think by default you are now the project's chief engineer, so you'd better begin an inspection. This ship must leave in a few hours. There must be some of Jarrasen's a.s.sistants about here somewhere, so I would suggest you find them.'

'Well, it's not really my field, but I'll do my best.'

'Meanwhile we must search the stores Monitor was having loaded,' the Doctor continued. 'There must be an interface connector in there somewhere.'

Twenty minutes later the Doctor gave a cry of satisfaction and pulled something out of the pile of cartons and packing material strewn across the hangar floor. It was a length of ribbon cable with a multi-pin plug on one end and a skullcap on the other. The inside of the cap was lined with silvery contact points.

With the others trailing anxiously behind him he carried it back into the Lander.

The plug fitted a socket on the side of Monitor's mainframe unit. The android sat beside it and carefully pulled the cap into place. The Doctor turned on the power.

Immediately lights started to come on across the panels and the screens flickered into life. The android gave a little gasp. 'I can feel the power flowing through the systems. It's almost like an extension of my body.' She smiled. 'Yes, I think I'll be able to fly the Lander all right.'

'I knew you could,' Susan said.

Ian felt dizzy with relief, but he knew it wasn't over yet.

He looked at the Doctor. 'So now we can take off... but counting the NC2s we brought, plus the surviving workers, can we carry... what... a hundred and fifty extra people? If only we could open the TARDIS at least we could take some of them with us.'

'This is no time for wishful thinking, Chesterton,' the Doctor admonished.

'What's the matter?' Barbara asked.

'Sorry, with all the confusion we didn't get a chance to tell you,' Ian said. 'This is going to come as a shock. Susan's key is lost and the Doctor's was stolen. We can't get into the TARDIS. We'll have to go to Mirath... if there's room.'

Barbara frowned, reached into the pocket of her slacks and pulled out a key on the end of a crumpled piece of ribbon.

'I've got Susan's key. She had it in her hand when the tower collapsed. I must have caught hold of it as I pushed her clear.'

They stared at her in astonished silence, which Ian broke with a hearty laugh. 'You have no idea how we've suffered over that.'

Barbara solemnly handed the key over to the Doctor.

'You know what we could do now,' said Susan excitedly.

'We could take the extra people on board the TARDIS, then have it loaded into the hold. That wouldn't increase the payload significantly.'