'I see,' said the voice. 'Is the Doctor available by any chance?'

'I'll see, sir. Who's calling?'

'Oh, just tell him it's an old friend.'

Benton pa.s.sed the phone to the Doctor. 'For you, Doctor. Says it's an old friend.'

The Doctor took the phone. 'h.e.l.lo?'

'Ah, Doctor,' said a familiar voice. 'I gather that the tables have been turned at Stangmoor?'

'You have gathered correctly,' said the Doctor acidly.

'Let me tell you exactly what's been going on..

Jo and Barnham had long ago run out of conversation.

They were sitting tensely, trying not to look at the creature in the Machine when Doctor Summers burst into the room.

'Jo, what the devil do you think you're doing? And you, Barnham! I've been looking for you, everywhere. I told you to stay in the Medical Wing. Come on!'

'Doctor Summers, he can't go,' pleaded Jo. 'We've got to stay by the Machine.'

'But you'll get yourselves killed.'

'We can't leave,' said Jo obstinately.

'Look, Jo, you know Barnham isn't really well yet and you know that thing is dangerous.' He turned to Barnham.

'Come on, now.'

Barnham looked worriedly from one to the other.

'Please, I can't... my head's hurting...'

As Barnham's concentration was weakened, the Machine began a low angry throbbing, and the strange sponge-like substance began to pulsate.

Doctor Summers stared at it in horror. 'That thing it's alive!'

'That's right,' said Jo fiercely. 'And unless Barnham stays here undisturbed undisturbed it will break loose and kill us all!' it will break loose and kill us all!'

The Doctor was concluding his account of recent events at Stangmoor. 'So you've lost, you see,' he concluded. 'The prison is in our hands, and UNIT has you surrounded.

Now, in the light of present circ.u.mstances, do you still intend to fire that missile at London?'

'I most certainly do, Doctor. And later, when this miserable planet is in ruins, I shall take over.'

'Aren't you forgetting something?'

'Am I, Doctor? What?'

'The dematerialisation circuit I took from your TARDIS. You can never leave Earth without it.'

On a previous encounter, the Doctor had removed the vital dematerialisation circuit from the Master's TARDIS which was why the Master, like the Doctor, was currently stranded on Earth.

There was a long silence.

'Are you offering me a deal, Doctor?'

'I am. Hand over that rocket and I'll give you back your dematerialisation circuit.'

'How very generous of you.'

'You can leave Earth and leave us in peace. Go and make trouble somewhere else.'

There was another pause.

'Well,' said the Doctor impatiently. 'What do you say?'

'Very well. You will bring the circuit to me at the hangar, Doctor. You, and you alone. Any sign of treachery, any interference from your UNIT friends and I shall launch the missile immediately.'

The Doctor heard a click as the phone was put down at the other end.

The Doctor turned to Benton. 'Can you contact the Brigadier for me?'

'Yes, Doctor. He'll be at the Mobile HQ by now.'

'Then get me on to him at once. He's got to cancel that attack.'

Doctor Summers was reluctantly preparing to leave the Process Chamber. 'If you're sure I can't do anything?'

'No, really,' Jo liked Doctor Summers, but she was wishing desperately that he would just go, before he distracted Barnham further.

'Very well. I've got a lot of wounded men to look after.

I'll be in the Medical Wing if you need me. Look after him, Jo and look after yourself.' He patted Barnham on the shoulder. 'Mind you do exactly as Miss Grant says.'

Doctor Summers hurried away.

Jo looked worriedly at Barnham. 'How are you feeling now?'

'I'm tired, but I'm all right.'

'Try and concentrate on keeping calm. It won't be much longer...'

The Doctor said, 'Don't you understand, Brigadier? You mustn't go anywhere near the Master. If he catches sight of a uniform, he'll fire that missile immediately.'

The Brigadier's voice was too confident for the Doctor's liking. 'Don't you worry, Doctor. Leave everything to us.'

'Will you do as I ask?'

'We'll cancel the attack, and I'll send a despatch rider to HQ for your circuit just in case.'

'What do you mean, just in case? Persuading him to make that exchange is our only chance!'

'Oh, I don't think so, Doctor. There are other ways to deal with him.'

'Now don't do anything stupid, Brigadier. The Master means what he says.'

The Brigadier remained infuriatingly cheerful. 'Don't you worry, Doctor. Over and out.'

'Lethbridge-Stewart, wait!' shouted the Doctor. But the RT was dead.

The Brigadier was feeling rather pleased with himself. The Doctor had been trying to deal with the Master for goodness knows how many years and now he he was about to do it for him. He turned to Major Cosgrove. 'I want you to get on to the Missile Control people. Confirm that they're to maintain radio link with us, and explode the missile when I give the word.' was about to do it for him. He turned to Major Cosgrove. 'I want you to get on to the Missile Control people. Confirm that they're to maintain radio link with us, and explode the missile when I give the word.'

'Right away, sir.'

'Captain Yates, you'll be in charge of the evacuation. I want the area around that hangar completely cleared within a ten-mile radius.'

'Right, sir.'

Cosgrove picked up the RT. 'Trap One to Missile Control...'

The Doctor was pacing about the Process Chamber.

Barnham sat with his hands on his knees, and the Machine was still.

'I don't see why you're so upset, Doctor,' said Jo. 'If you give him back the circuit, and he hands over the missile..

The Doctor sighed. 'You don't understand, do you Jo?

Once he gets that circuit back he's free to roam through Time and s.p.a.ce. We'd never catch him.'

Jo could hear the yearning in the Doctor's voice.

Suddenly she realised what it would mean to him to give the Master his freedom, while he himself remained an exile.

Sadly Jo said, 'You'll just have to give in, Doctor. The Master's got the missile, and all we've got is this wretched Machine.'

'There's no need to point out the obvious, Jo ' The Doctor broke off, staring hard at her. 'What did you say?'

'I said all we've got is the Machine.'

'That's it! That's the answer! We've got the Machine and we've also got our friend Barnham.'

Barnham looked puzzled. 'I don't understand.'

The Doctor rubbed his hands. 'With a little help from you, old chap, we're going to destroy this Machine and the Master both at the same time.'

The Master was busy dismantling the abort circuit on the missile control console. He smiled. 'Just in case anyone tries to be clever...'

To everyone's relief the dome had been put back on the Keller Machine, concealing the mind parasite inside.

Benton hurried into the Process Chamber. 'Everything's laid on, Doctor.'

'Thank you, Sergeant. Are you ready, Barnham? Do you understand what to do?'

'I think so...'

Reluctantly, Barnham approached the Machine. It began throbbing angrily.

'Don't worry, it can't hurt you,' said Jo encouragingly.

s.c.r.e.w.i.n.g up his courage, Barnham seized the Machine and lifted it up. The throbbing stopped immediately.

'Well done, old chap,' said the Doctor. 'Just remember, whatever you do, don't drop it. Now then, off we go. Easy does it, that's the idea.'

Slowly Barnham carried the box towards the door. The others followed.

When the Doctor arrived at the Mobile HQ followed by his entourage, he found the Brigadier distinctly crestfallen.

'We tried to explode the missile on the ground with the abort circuit Doctor, but nothing happened.'

'Well, what did you expect?' said the Doctor scorn-fully.

'The Master may be a scoundrel, but he is a scientist. He'll have disconnected the abort mechanism.'

'Which means there's only one thing for it, Doctor.

You'll have to go through with your deal and give him back his wretched circuit.'

'Is it here?'

The Brigadier looked at Major Cosgrove who said calmly, 'Just arrived, sir.' He handed the Doctor a small sealed packet.

The Doctor ripped it open and took out a little box.

Inside it was the Master's dematerialisation circuit, a complicated little affair that looked vaguely like the model of an atom. The Doctor looked sadly at it.

'I know how you feel, Doctor,' said the Brigadier sympathetically. 'I hate to see the Master escape as much as you do.'