Nick answered her. 'From eternity, love. I'm an Angel. Michael makes what he calls Angels. He thinks he's God.'

'No I don't.'

The blue eyes were fixed upon him. 'You're God to me. Shall I tell you what's going to happen to you, Michael? You're going to have the same life that God had.' Nick gave a narrow amused little smile. 'And God has had a terrible life.' He sniffed. 'He keeps trying to do good.'

'I'm going to put you where you can do no harm. You know how they seal radioactive material away? They drop it into salt caverns a mile deep and the salt migrates and closes, so nothing can get out. I'm going to put you into one of those caverns, Nick. And I'll give you companions. You can make a kind of porn with them, if that's all you think they're good for. They can be your little demons.'

Nick was sourly resigned. 'I always said. Prison went with the territory.'

'Then maybe prison is what you want.'

'Watcha.' Nick made his fingers into a pistol.

You could have been such a handsome devil, Nick. You could have been one of those bitchy stand-up comedians who trade on their whiff of cordite, and who mellow with success. A chat show host? Or a racing car driver, something flash with sporting gear and sponsorship but nothing actually athletic. Anything that required aggression and the common touch. What you will need to become now, is a philosopher.

'Be yourself,' said Michael, and cast him down.

The air folded around Nick like a pair of closing buttocks.

The room was still, except for the sweat trickling down Ebru's forehead.

'Michael. What was that?'

Michael sat up. He was very weak, but he had been fed and rehydrated. He felt light as if his bones were hollow. Michael felt like a bird.

'I'll explain,' he promised. 'Excuse me while I dress. There is something I need to do.'

'You will stay here, Michael,' said Ebru, folding her arms. A trolley with food came. A cheerful black lady came. 'I am your nutritionist,' she announced. 'This may not look good, but it is delicious.' It was a kind of pabulum with mashed bananas. Eating it gave Michael stomach cramps, but soothed his throat.

It was night by the time the doctor had examined him, and the discharge papers were filled in. 'Thank you, Ebru, thank you for helping me. Do you think you could come with me to the lab?'

Ebru took him by the arm and walked him to Goodge Street tube station. Michael was too weak to talk over the noise of the train. It lurched and made him feel queasy.

He thought instead of what he was going to do. He saw himself setting the chicks free in the park. They were nervous at first, clustering around his feet, their down blown in different directions by the wind. Then suddenly they spread out around him, showing against the dark grass as if fluorescent.

As Ebru led him from Lambeth North, Michael told her everything that had happened since the first day of the project.

'I would not even begin to believe,' said Ebru. 'If I had not seen with my own eyes.' She pointed outward from her cheekbones as if warding off the evil eye.

'There will come a time, Ebru, when you won't remember this. All you'll remember is that I was ill. But you'll think more kindly of me.'

'I always thought kindly of you, Michael.'

Shafiq was at the security desk. Ebru called to him. He looked up in alarm. 'Shafiq, it is only us,' she said. Reassurance seemed to slim Shafiq down; he grew sleeker. He stood up grinning. 'Michael. You are all right! They said you were…' He looked at Ebru, for reassurance. 'Not well.'

'I'm OK, Shafiq. I… I would like us to let the birds loose.'

Shafiq and Ebru glanced at each other.

Michael insisted. 'They can't die, Ebru. They don't need to eat.'

'So, they stay cold and miserable all winter long,' she said.

'These are the ones we killed.'

Ebru said, 'No, they're not. See for yourself.'

She helped him down the corridor, which was longer than he remembered, to the darkroom door. She swung it open. The light, as he had left it, was on. They would have seen light for a week. Ebru picked one of them up and gave it to him. Already, the creature was bigger, older, than any of their chicks had been. It looked up at Michael with reptilian eyes.

'They are already different,' Ebru said.

Michael smiled at himself. 'So, I could have set free a race of immortal superhens in Archbishop's Park.' He saw them chasing children. He saw vermin control gassing them to no effect.

Shafiq tried to help. 'We thought we might sell them to a chicken farmer.'

'Yuck,' said Michael. He thought of someone eating Angels.

There was only one thing to do, really, faced with it.

'Goodbye, then,' he said to his children, and he sent them to rejoin their immortal selves. The air throughout the darkroom roiled as if full of evaporating gas fumes. The chicks were gone.

Shafiq gasped and looked round-eyed at Michael. Michael didn't have to look at him to know that. He kept his eyes averted.

'It's just something temporary, Shafiq. It's just something temporary that I can do.'

And it will be a good sign when it stops, for that will mean the wastes have stopped howling.

Michael sighed and slapped his thigh, as if closing a boot, and he asked Ebru, 'Well, did we prove anything?'

Ebru paused for a moment, as if asked to cross a chasm on a rope bridge.

Michael asked again: 'Our experiment. Did we learn anything by killing all those chickens?'

Ebru considered. 'We prove they learn. But we also prove that what they had to learn was in their brains to begin with.'

'Is that something worth knowing?'

'Yes,' Ebru said, and then again more fiercely, 'Yes, it is.'

'Was it worth killing them?'

Ebru sighed. 'You need to find your own answer for that, Michael.'

Michael rubbed his eyes. Was there a chair? He needed to sit down. 'I know what the chicken's answer would be.'

Ebru shook her head. 'But you don't, Michael. You can't know. That is the whole difficulty.'

She took him by one arm, and spurred by her example, Shafiq took the other. They led him hobbling back to the soon-to-be-emptied office where he could sit down.

Michael slumped into his chair. 'We're real,' he said. 'We can't undo what we've done.' He surveyed the filing cabinets, the dark PC screens. 'That's what makes us real.'

Part III. What do you want for Christmas?

For a while, Michael stalled.

The project wound down. The results were conclusive. The learning process caused a range of chemical changes in nerve cells. The pathway of that chemical change through the brain was common. Some neural pathways for learning about light seemed to be pre-established, at least in chickens.

Michael began work on a small, publishable paper, for a respected scientific journal. He let Emilio go to his new job early. Shafiq was fine; he simply went back to his agency and a new post. Geoffrey Malterton at the Council found another project that could use their facility. He was pleased: he would end up being the lab's new Director, not Michael. It was left to Michael and Ebru to turn out the lights on the lab one last time, and share a quiet drink at the Pineapple.

Michael still had his teaching once a week, which was a living, not a calling. He explained the basics of neurology to students for whom it was not a calling either. It was a way of increasing their earning potential. They argued with him about each and every mark on their phase tests and worked out from their percentages so far whether or not getting an A on the final test would make any difference to their overall grade. If it wouldn't, then they would stop studying.

Christmas came, full of tinsel and loneliness. The students left for home, except the ones who had no home. They stayed on in student accommodation playing disconsolate dance music.