'Reverse the polarity of the binary transmission decoder unit and link it to the reception unit -' muttered the Doctor.

You'd better hurry up, thought Jo. She wasn't sure how much time had pa.s.sed since they'd left the brood chamber, but she knew that there couldn't possibly be much more than a minute left.

The Doctor took a step back from the creature, a cl.u.s.ter of wires in each hand. 'Well, Jo, here goes,' he said, and pushed the two cl.u.s.ters together.

There was a crackle, a shower of sparks, and then a very loud bang.

The Doctor stood up, turned to Jo, his expression serious.

'It didn't work, did it?' she said quietly.

'It might have done,' said the Doctor. 'I put the whole of the residual voltage in that thing's batteries through the circuit in about three-fifths of a second. It should have been long enough.'

'Long enough to what?'

'Long enough to scramble the detonation mechanisms on the incoming missiles.'

'And if it wasn't?'

'Well, Jo,' said the Doctor slowly. 'If we're still alive after about thirty seconds, I think we can say it worked.'

Jo looked away, swallowed.

Thirty seconds.

She reached out and took the Doctor's hands, then let herself be hugged. She tried to imagine what it would be like, if the bomb went off. Would she feel anything? Or would she simply cease to exist?

Fifteen seconds, she thought. Fourteen. Thirteen. No. They're too precious to count.

She stared over the blurry edge of the Doctor's jacket at the sunlight streaming in through the window. Felt the warmth of it.

The sun will still shine, she thought. Even if - 'Time's up, Jo,' said the Doctor's voice softly. 'I think we've won.'

Epilogue.

Aveil of smoke was still hanging over Kebir City, smoke that was scented of honey and roses and cloves. Jo stared through it at the low red disc of the sun setting over the distant domes of the People's Palace. Then she turned to the Doctor and Mike Yates, who were standing on the dry shingle beach, looking out over the Mediterranean.

The sea was smooth, oily; Jo could see grey shapes moving in the haze of smoke, hear the clatter of engines.

Helicopters: American helicopters, searching for bodies from the Eisenhower Eisenhower.

She shuddered.

'After Tahir picked me up we had a look for Vincent's body,' Mike was saying. 'We had a job on finding it; I thought it had been taken by the Xarax.'

'But you did find it?' Jo was surprised that she was so concerned.

Vincent had been a murderer; but his death still touched her.

Mike nodded. 'We burned it, in case it was infected. The Sakir Sakir insisted.' He paused, turned to the Doctor. 'What did you do to the Xarax?' insisted.' He paused, turned to the Doctor. 'What did you do to the Xarax?'

'Well basically I told them to switch themselves off.' He looked at Jo, gave her a rueful smile. 'I don't think humanity's ready for such a tool yet, do you?'

Jo shook her head.

'Is that all they were?' asked Mike. 'A tool kit?'

The Doctor nodded. 'A biological tool kit, but a tool kit nonetheless. They just obey whatever program they're given. I imagine that originally they existed as very sophisticated symbiotes.

Then some intelligent species discovered them, adapted them for their own ends, gave them control mechanisms that could be used by other species.' He paused. 'I realized that as soon as Zalloua told us how easily he could control the Xarax. Even though he said he was making mistakes, for him to be able to do it at all there had to be some pre-existing control mechanism.' He glanced at Jo. 'Of course, I should have realized that with a built-in control mechanism, it really wasn't very likely that Zalloua was having the problems he was claiming to have.'

'So how did they get to Earth?' asked Jo.

The Doctor shrugged. 'By accident, possibly. Or maybe they were dropped off deliberately; perhaps their masters thought they were doing humanity a favour. But of course they reckoned without humans like Monsieur Zalloua - '

He broke off as the Sakir Sakir Mohammad came into view, his head bowed. Mohammad came into view, his head bowed.

'It is as you told us, Doctor,' he said. 'They are all gone.'

'Everyone in the city?' asked Mike.

The Sakir Sakir shrugged. 'Tahir and Jamil have checked all the districts. shrugged. 'Tahir and Jamil have checked all the districts.

No-one answers them when they call. There may be a few that are hiding, but -' He broke off, shaking his head.

'Burnous Asi was empty when we came through it,' said Mike.

'Doctor, how far do you think the Xarax would have spread?'

The Doctor was staring out to sea. The helicopters were further away now, the sound of their engines fading. The smoke haze had thinned a little, revealing a gunmetal-grey horizon.

'Doctor?' asked Jo, when he didn't speak for a while.

'They wouldn't have bothered much with small population centres,'

said the Doctor at last. 'Not when they were fighting for survival. The Kebiriz coastal towns should be all right, I think. And the Gilteans'

desert oases, if they weren't too near the nest.'

There was a long silence.

'Kebiria was a country of six million people,' said the Sakir Sakir eventually. eventually.

There was another long silence. Mike slowly walked away, his hands in his pockets. After a while he picked up his binoculars and looked at the city through them, perhaps hoping to spot some sign of life.

'What will you do now, Sakir Sakir?' asked Jo.

The old man shook his head. 'I don't know. Start again, I suppose.

But we will not call the country Kebiria any more.' He paused. 'And we will not call it Giltea either. I will think of a new name.'

Somewhere behind them, a man's voice began a soft recital, half-spoken, half-chanted. At some points, other voices joined in.

'I must join my people,' said the Sakir Sakir. He walked quickly up the shingle slope to the sea wall. Beyond it, Jo saw the jeeps drawn up in a circle in the middle of the wide concrete promenade, in front of the tourist hotels. Someone had put a camel-wool tent up; the voices appeared to be coming from inside it.

An encampment, thought Jo. A desert encampment in the middle of a city.

She turned back to the Doctor. 'They won't be able to bury any of them, will they? They'll have to burn them all.' She was thinking of Catriona. Catriona who had died saving her life.

The Doctor nodded. 'But they'll probably put up a memorial.'

It's not much compensation.' Jo stared at the gunmetal horizon until her eyes watered. She thought about the Brigadier, shooting the copies of the Doctor and herself with that cold expression on his face.

About the guard dying in the prison. About the little girl dying in Vincent's camp.

All the deaths.

'Perhaps I could be a reporter, like Catriona,' she said at last. 'I could tell people what it's really like. How horrible it is.'

The Doctor smiled at her. 'Not everything's horrible, Jo. I know it seems that way sometimes, but - '

He broke off, looked up at the jeeps. Jo heard the sound of raised voices.

' - new state ... Kebiriz welcome ...' The Sakir Sakir's voice.

'I would die first! After what the Kebiriz have done to us we can never allow them to be a part of our country. It must be ours ours!'

'The conflict must come to an end, and the only way is to let the Kebiriz take part - '

'We cannot! I will kill them first!'

Jo started up the shingle towards the makeshift encampment, but the Doctor caught her arm.

'It's better not to interfere, Jo. You don't know enough about this quarrel to decide - '

But Jo shook her head, and shook off his arm.

'We can't just let it start again, Doctor,' she said. 'We've got to do something something.'

PAUL LEONARD is the author of the highly acclaimed VENUSIAN LULLABY, a Missing Adventure featuring the first Doctor, Barbara and Ian.