' You get back here You get back here. That Machine of yours has broken loose.

It's moving around the prison. It's killed Lenny Vosper, and it nearly killed me.'

'I tell you I can't leave.'

As far as the Master was concerned, the Machine could kill everyone in the prison and welcome. Mailer's next words forced him to think again. 'Now you listen to me, mate. My mob won't stay here with that thing on the loose.

They'll start running, and I'll be running with them.'

'But you'll be caught.'

'Maybe so. But if I get caught, remember, so do you.

They'll be asking where that missile is and I just might tell them. Think about it.'

There was a click, as Mailer slammed down the phone.

The Master sighed. He really should have killed Mailer once he was no longer useful. It was always a mistake to be too compa.s.sionate. He turned to Mike Yates, and swung round the swivel chair so that his captive faced him. 'You can stop shamming unconsciousness, Captain Yates. I hope you're quite comfortable?'

Mike opened his eyes, still a little dazed from the combination of his wound, the fall, and the subsequent rough handling. 'Why?'

'Why did I take the missile? I intend to use it.'

'You'll never be able to fire it, it's too complex.'

The Master chuckled, glancing at the firing control console which he had already rigged up in the corner of the office hut.

'Nonsense. The mechanism is childishly simple.

Besides, I have all the technical a.s.sistance I need.' He waved towards the open door of the hut, through which could be seen a team of uniformed men hard at work readying the missile for launching.

'I was going to ask you about those soldiers.'

'Hired mercenaries in faked uniforms. Everything's a matter of money these days, my dear Captain. Now, if you'll excuse me?'

The Master turned away, then paused in the doorway.

'Ah, yes, you're probably wondering why you are still alive?'

'It did cross my mind.'

'In the event the extremely unlikely event of your UNIT friends finding us before the missile is ready to fire, you will make a very useful hostage. Remember that!'

The Master left.

As soon as he was out of sight, Mike Yates set to work, sawing his bonds against the steel strut at the back of the chair. It was a slim chance, but so long as there was any chance at all he would go on trying.

Mailer looked disgustedly at the Doctor, Jo and Barnham.

'Well done, Fuller, where did you find 'em?'

'Outside in the courtyard,' said Fuller. 'Waving to a helicopter.'

'What? Did it see them?'

'Dunno. I don't think so. Anyway, it's cleared off now.'

Mailer looked uneasily at Barnham, who smiled back at him.

Mailer shivered, thinking of what he too might have become. 'Get that zombie out of here, he gives me the creeps.' One of the convicts led Barnham away. Mailer turned back to the Doctor. 'I don't know what we're going to do about you, Doctor.'

The Doctor leaned forward, and Mailer raised the automatic. 'Back ofll'

'Mailer, why why are you helping the Master?' demanded the Doctor. are you helping the Master?' demanded the Doctor.

'Simple. I'm helping him because he's helping me.'

'What did he promise you?'

'Money. A free pardon. A ticket to anywhere in the world.'

'Do you really believe he'll keep his promises?'

'Why not?'

'He doesn't care if you live or die,' said Jo. 'He's using you.'

Mailer shrugged. 'He's using me, I'm using him. Can you make me a better offer, Doc?'

The Doctor considered. 'Let us go free and I'll do my best for you.'

Mailer chuckled. 'Well, if that's your best offer, it really ain't good enough. All right, Fuller, wheel 'em out. Back to the condemned cell.'

The Brigadier was back in his mobile HQ with Major Cosgrove. 'I tell you I know exactly where that missile is, Major.' He pointed to a wall map with his swagger stick.

'Stangmoor Prison. It all adds up. Benton saw a Black Maria when the convoy was ambushed, and I saw the Doctor and Miss Grant. The Master's taken over the prison and I'm convinced he's using it as a hideout for the missile.'

Cosgrove nodded. 'I a.s.sume we'll be taking the place, sir?'

'Major Cosgrove, have you ever seen seen Stangmoor Prison? Stangmoor Prison?

It used to be an old fortress. You'd need an army to get in there.'

And for political reasons, thought the Brigadier, an army was just what they couldn't have. The place would have to be taken with his own relatively small force of UNIT troops.

Major Cosgrove was thinking hard. 'A fortress, you said, sir? I suppose there couldn't possibly be some kind of secret entrance an underground tunnel, something like that?'

The Brigadier gave him a look.

Unperturbed, Cosgrove said, 'I've got a plan of the prison here, sir.'

Trust Cosgrove to have everything ready, thought the Brigadier. He studied the plan and blinked. 'It appears that you're right, Major Cosgrove.' He pointed to the map.

'There's a sort of underground pa.s.sage, here. It doesn't lead into the prison itself of course, but it'll get us to the far side of the inner courtyard.'

Cosgrove beamed. 'I say, it's almost like something in a film, isn't it, sir?'

The Brigadier gave him another quelling look, and resumed his study of the map.

Suddenly a voice crackled from the RT 'Greyhound Seven to Trap One.'

Cosgrove flicked a switch. 'Go ahead, Trap One here.'

'I'm on observation at the prison gates, sir. A black limousine has just entered the prison. Bearded pa.s.senger in the back.'

'It must be the Master,' said the Brigadier. 'They wouldn't let anyone else inside anyway. That settles it, Cosgrove, we're going to take that prison.'

'By using the underground pa.s.sage, sir?'

'Yes,' said the Brigadier. To prove that Cosgrove didn't have a monopoly on good ideas, he added, 'And by using a Trojan horse!'

The Doctor and Jo were playing draughts in the condemned cell. The door was flung open and the Master appeared dramatically in the doorway. 'Ah, Doctor!'

The Doctor held a finger to his lips. 'Sssh!' He studied the board for a moment, then made his move, taking two of Jo's pieces. 'There!'

The Master wasn't used to being ignored. 'I was about to say, Doctor '

'Ssh!' said Jo. She moved one of her pieces in a complicated zig-zag across the board, taking nearly all the Doctor's pieces, and conclusively winning the game.

'There!'

The Doctor rose and yawned. 'The trouble with this game is it's really too simple,' he said sulkily. 'I'm really only used to three-dimensional chess.'

He stretched out on the bed and lay back, his hands behind his head.

The Master sighed. 'All right, Doctor, I have allowed you your little gesture of defiance. Now perhaps we,can talk seriously?'

'I suppose you're going to ask me to control that mind parasite for you?'

'I am.'

'Well, I can't. No one can.'

'You underestimate yourself, Doctor. I'm sure you are perfectly capable of controlling it for a time at least.'

'Even if I could control it, why should I help you?'

'To save lives?' suggested the Master. 'A number of people have died already.'

'Most of them hard-case criminals who were helping you., 'Very well then. To save one particular life.'

'My own?'

The Master shook his head. He stepped aside and Mailer came into the cell, the inevitable automatic in his hand. Fuller closed the door behind him.

The Master nodded, not towards the Doctor, but to Jo Grant.

'Don't take any notice of him, Doctor,' said Jo. 'He's bluffing.'

'Am I? I a.s.sure you, that unless the Doctor agrees to help me, Miss Grant, Mailer will shoot you. Here and now.'

Mailer c.o.c.ked the automatic.

There was a long pause at least, it seemed long to Jo Grant.

Then the Doctor rose, and began pacing thoughtfully about the cell. 'It's only a theory, but I think there may be a way to inhibit that Machine's power of movement.'

'You'll never have a better chance to put your theory to the test, Doctor.'

'Where is the thing now? Still wandering about?'

Mailer said, 'One of the lads said it's back in the Process Chamber.'

'Temporarily glutted no doubt,' said the Master. 'Well, Doctor?'

'I'll need a lot of equipment.'

'Stangmoor is a progressive prison, Doctor,' said the Master expansively. 'The contents of the Prison Workshop are at your disposal.'

'All right. I'll give it a try.'

The Doctor moved towards the door.

'All right, Fuller, let us out,' called the Master.

The door opened and Mailer, the Doctor and the Master left the cell.