'It looks like a rubbish tip to me.' Walter surveyed the deep furrows, the small pits with planks laid across them, the yellow clay, the pieces of brick and stone apparently thrown haphazardly to the edges of the site.

'Yes, but where did it come from? You know, Walter, from dust to dust…'

And his voice trailed off when he realised that they were being watched. A woman, wearing rubber boots and a bright red sweater, was standing in the far corner of the excavations. 'Hello love!' Walter shouted to her, 'We're police officers. What are you up to?' His voice had no echo as it passed over the freshly dug earth.

'Come on down and see!' she called back. 'But there's nothing here!

Nothing's been touched overnight!' In confirmation of this, she kicked a piece of plastic sheeting which remained firmly in place. 'Come on, I'll show you!'

Hawksmoor seemed to hesitate, but at this moment a group of children turned the corner into King William Street and he suddenly descended into the site by means of a metal ladder. Tentatively he crossed around the edge of the open pits, smelling the dankness of the earth as he did so. It was quieter here beneath the level of the pavement, and he lowered his voice when he reached the archaeologist: 'What have you found here?'

'Oh, flint blocks, some bits of masonry. That's a foundation trench there, you see.' As she talked she was scraping the skin off the palm of her hand. 'But what have you found?'

Hawksmoor chose to ignore the question. 'And how far down have you reached?' he asked her, peering into a dark pit at his feet.

'Well it's all very complicated, but at this point we've got down to the sixth century. It really is a treasure trove. As far as I'm concerned we could keep on digging for ever'. And as Hawksmoor looked down at what he thought was freshly opened earth, he saw his own image staring back up at him from the plastic sheeting.

'Do you mean this is the sixth century here?' he asked, pointing at his reflection.

'Yes, that's right. But it's not very surprising, you know. There's always been a church here. Always. And there's a lot more to find.'

She was certain of this because she saw time as a rock face, which in her dreams she sometimes descended.

Hawksmoor knelt down by the side of the pit; as he took a piece of earth and rubbed it between his fingers, he imagined himself tumbling through the centuries to become dust or clay. 'Isn't it dangerous,' he said at last, 'To dig so close to the church?'

'Dangerous?'

'Well, might it fall?'

'On us? No, that won't happen, not now.'

Walter, who had been examining the wooden supports which held up the church, had joined them: 'Not now?' he asked her.

'Well, we did find a skeleton recently. Not something you would be interested in, of course.'

But Walter was interested. 'Where did you find it?'

'It was there, next to the church, where the pipes are being laid.

They were pretty new, too.' Hawksmoor glanced in the direction to which she pointed, and he could see soil which was the colour of rust.

He looked away.

'And how new is new?' Walter was asking her.

'Two or three hundred years, but we haven't completed our tests yet. It may have been a workman who was killed when the church was rebuilt.'

'Well,' said Hawksmoor. 'It's a theory, and a theory can do no harm.' Then he suggested to Walter that they might leave, since time was pressing, and they ascended into the street where once more they heard the noises of traffic. He looked up at an office-building on the other side, and saw the people moving around in small lighted rooms.

And it was while Walter lingered with the policemen who were still methodically searching the immediate area of the murder that Hawksmoor noticed the tramp kneeling by the corner of Pope's Head Alley, opposite the north wall of St Mary Woolnoth. He seemed at first to be praying to the church but then Hawksmoor realised that, although the pavement was still damp after the morning rain, he was finishing a sketch in white chalk. He crossed the road slowly and stood by the side of the kneeling man: for a moment he looked with horror at his hair, which was thickly matted into slabs like tobacco.

The tramp had drawn the figure of a man who had put a circular object up to his right eye and was peering through it as if it were a spy glass, although it might equally have been a piece of plastic or a communion wafer. He paid no attention to Hawksmoor, but then he looked up and they stared at each other; Hawksmoor was about to say something when Walter called out and beckoned him towards their car. 'We ought to go back,' he was saying when Hawksmoor came up to him.

'They've found someone. Someone's confessed.'

Hawksmoor drew his hand three times across his face. 'Oh no,' he muttered, 'Oh no. Not yet.'

The young man sat, with bowed head, in a small waiting room; as soon as Hawksmoor saw his hands, small with the nails bitten down to the flesh, he knew that this was not the one. 'My name is Hawksmoor,' he said, 'and I am involved with this enquiry. Can you go in?'

He opened the door to the interview room. Tn you go. Sit down over there. How do you do? Have they treated you well, Mr Wilson?' There was a muttered reply which Hawksmoor did not care to hear: the man sat down on a small wooden chair and started rocking slightly, as if he were trying to comfort himself. At this point Hawksmoor did not want to go on; he did not want to enter this chamber of tortures and look around within it. 'I'm going to interview you,' he said very quietly, 'with regard to the murder of Matthew Hayes, whose body was found at the church of St Mary Woolnoth at about 5.30 a.m. on Saturday, October 24. The boy was last seen alive on Friday, October 23. You have given yourself up. What do you know about his death?' Walter came in with a note-book, as the two men stared at each other across the table.

'What do you want me to say? I've already told them.'

'Well, tell me. Take your time. We have plenty of time.'

'It doesn't take any time. I killed him.'

'Who did you kill?'

'The boy. Don't ask me why.' And once more he bowed his head; but he looked up at Hawksmoor in the silence which followed, as if pleading with him to make him go on, to make him say more. He was hunched forward, rubbing his hands against his knees, and in that instant Hawksmoor saw the man's thoughts as a swarm of small flies trapped in a bare room, swerving to one side and then another in an effort to break free.

'Well I am asking you why,' he said gently, 'I have to know why, Brian.'

He did not register the fact that Hawksmoor knew his name. 'What else can I do, if that's the way it is? I can't help it. That's the way it is.'

Hawksmoor examined him: he saw that his fingers, now clenched, were stained with nicotine; he saw that his clothes were too small; he saw the carotid artery pulsing on the side of his neck, and he restrained an impulse to touch it. Then without a trace of eagerness he enquired, 'And how do you go about killing, when you get the chance?'

'I just get hold of them and I do it. They need to be killed.'

They need to be killed? That's a bit strong, isn't it?'

'I don't see why it is. You should know -' And he was about to say something when, for the first time, he noticed that Walter was standing behind him, and he stopped short.

'Go on. Would you like a glass of water, Brian?' With a sudden gesture Hawksmoor motioned Walter out of the room. 'Go on, I'm listening. It's just you and me.'

But the moment had gone. 'Well it's up to you to do something then, isn't it?' The young man concentrated upon a small crack in the floor. 'I can't be held responsible once I've told you.'

'You haven't told me anything I didn't know.'

Then you know everything.'