Billy opened his mouth. His lips were ruddy and slick, as if he were wearing lipstick.

'Now ...' he said, trying to speak between painful breaths. '... now what shall we do?'

The act of speaking seemed too much for him. He made a gagging sound in the back of his throat, and pressed his hand to his mouth. Cleve moved aside as Billy stood up and stumbled across to the bucket in the corner of the cell, kept there for their night-wastes. He failed to reach it before nausea overtook him; fluid splashed between his fingers and hit the floor. Cleve looked away as Billy threw up, preparing himself for the stench he would have to tolerate until slopping-out time the following morning. It was not the smell of vomit that filled the cell, however, but something sweeter and more cloying.

Mystified, Cleve looked back towards the figure crouching in the corner. On the floor between his feet were splashes of dark fluid; rivulets of the same ran down his bare legs. Even in the gloom of the cell, it was unmistakably blood.

In the most well-ordered of prisons violence could - and inevitably did - erupt without warning. The relationship of two cons, incarcerated together for sixteen hours out of every twenty-four, was an unpredictable thing. But as far as had been apparent to either prisoners or officers there had been no bad blood between Lowell and Nayler; nor, until that scream began, had there been a sound from their cell: no argument, no raised voices. What had induced Nayler to spontaneously attack and slaughter his cell-mate, and then inflict devastating wounds upon himself, was a subject for debate in dining-hall and exercise yard alike. The why of the problem, however, took second place to the how. The rumours describing the condition of Lowell's body when found defied the imagination; even amongst men inured against casual brutality the descriptions were met with shock. Lowell had not been much liked; he had been a bully and a cheat. But nothing he'd done deserved such mutilation. The man had been ripped open: his eyes put out, his genitals torn off. Nayler, the only possible antagonist, had then contrived to open up his own belly. He was now in an Intensive Care Unit; the prognosis was not hopeful.

It was easy, with such a buzz of outrage going about the Wing, for Cleve to spend the day all but unnoticed. He too had a story to tell: but who would believe it? He barely believed it himself. In fact on and off through the day - when the images came back to him afresh -he asked himself if he were entirely sane. But then sanity was a movable feast wasn't it?; one man's madness might be another's politics. All he knew for certain was that he had seen Billy Tait transform. He clung to that certainty with a tenaciousness born of near-despair. If he ceased to believe the evidence of his own eyes, he had no defence left to hold the darkness at bay.

After ablutions and breakfast, the entire Wing was confined to cells; workshops, recreation - any activity which required movement around the landings - was cancelled while Lowell's cell was photographed and examined, then swabbed out. Following breakfast, Billy slept through the morning; a state more akin to coma than sleep, such was its profundity. When he awoke for lunch he was brighter and more out-going than Cleve had seen him in weeks. There was no sign beneath the vacuous chatter that he knew what had happened the previous night. In the afternoon Cleve faced him with the truth.

'You killed Lowell,' he said. There was no point in trying to pretend ignorance any longer; if the boy didn't remember now what he'd done, he would surely recall in time. And with that memory, how long before he remembered that Cleve had watched him transform? Better to confess it now. 'I saw you,' Cleve said, 'I saw you change...'

Billy didn't seem much disturbed by these revelations.

'Yes,' he said. 'I killed Lowell. Do you blame me?' The question, begging a hundred others, was put lightly, as a matter of mild interest, no more.

'What happened to you?' Cleve said. 'I saw you - there - ' he pointed, appalled at the memory, at the lower bunk, 'you weren't human.'

'I didn't mean you to see,' the boy replied. 'I gave you the pills, didn't I? You shouldn't have spied.'

'And the night before ...' Cleve said, 'I was awake then too.'

The boy blinked like a bemused bird, head slightly cocked. 'You really have been stupid,' he said. 'So stupid.'

'Whether I like it or not, I'm not out of this,' Cleve said, 'I have dreams.'

'Oh, yes.' Now a frown marred the porcelain brow. 'Yes. You dream the city, don't you?'

'What is that place, Billy?'

'I read somewhere: the dead have highways. You ever hear that? Well... they have cities too.'

'The dead? You mean it's some kind of ghost town?'

'I never wanted you to become involved. You've been better to me than most here. But I told you, I came to Pentonville to do business.'

'With Tait.'

That's right.'

Cleve wanted to laugh; what he was being told - a city of the dead? - only heaped nonsense upon nonsense. And yet his exasperated reason had not sniffed out one explanation more plausible.

'My grandfather killed his children,' Billy said, 'because he didn't want to pass his condition on to another generation. He learned late, you see. He didn't realize, until he had a wife and children, that he wasn't like most men. He was special. But he didn't want the skills he'd been given; and he didn't want his children to survive with that same power in their blood. He would have killed himself, and finished the job, but that my mother escaped. Before he could find her and kill her too, he was arrested.'

'And hanged. And buried.'

'Hanged and buried; but not lost. Nobody's lost, Cleve. Not ever.'

'You came here to find him.'

'More than find him: make him help me. I knew from the age of ten what I was capable of. Not quite consciously; but I had an inkling. And I was afraid. Of course I was afraid: it was a terrible mystery.'

'This mutation: you've always done it?'

'No. Only known I was capable of it. I came here to make my grandfather tutor me, make him show me how. Even now ...' he looked down at his wasted arms,'... with him teaching me ... the pain is almost unbearable.'

'Why do it then?'

The boy looked at Cleve incredulously. 'To be not myself; to be smoke and shadow. To be something terrible.' He seemed genuinely puzzled by Cleve's unwillingness. 'Wouldn't you do the same?'

Cleve shook his head.

"What you became last night was repellent.'

Billy nodded. 'That's what my grandfather thought. At his trial he called himself an abomination. Not that they knew what he was talking about of course, but that's what he said. He stood up and said: "I am Satan's excrement - ".' Billy smiled at the thought. ' " - for God's sake hang me and burn me." He's changed his mind since then. The century's getting old and stale; it needs new tribes.' He looked at Cleve intently. 'Don't be afraid,' he said. 'I won't hurt you, unless you try to tell tales. You won't do that, will you?'

'What could I say that would sound like sanity?' Cleve returned mildly. 'No; I won't tell tales.'

'Good. And in a little while I'll be gone; and you'll be gone. And you can forget.'

'I doubt it.'

'Even the dreams will stop, when I'm not here. You only share them because you have some mild talents as a sensitive. Trust me. There's nothing to be afraid of.'

The city -'

'What about it?'

"Where are its citizens? I never see anybody. No; that's not quite true. I saw one. A man with a knife... going out into the desert...'

'I can't help you. I go as a visitor myself. All I know is what my grandfather tells me: that it's a city occupied by dead souls. Whatever you've seen there, forget about it. You don't belong there. You're not dead yet.'