'People used to be glad to pay to touch it, you know. They were disappointed when the injunctions forbade relics to be shown for lucre.'

'It is quite large, I imagine?'

He nodded. 'There is an illustration in the library, if you would care to see.'

'I would. Thank you. Tell me, who found the relic missing?'

'I did. I found the desecrated altar too.'

'Pray tell me what happened.' I sat down on a projecting buttress. My back was much better, but I did not wish to stand around for too long.

'I rose towards five as usual, and came to prepare the church for Nocturns. There are only a few candles lit before the statues at night, so when first I came into the church with my assistant, Brother Andrew, we noticed nothing amiss. We went into the choir; Andrew lit the candles at the stalls and I set the books open at that morning's prayers. As he was lighting the candles Brother Andrew saw a trail of blood on the floor, and called out. The trail led-' he gave a shuddering sigh '-into the presbytery. There, on the table before the high altar, was a black cock, its throat cut. God have mercy on us, black bloodstained feathers lying on the very altar, a candle lit on either side in satanic mockery.' He crossed himself again.

'Would you show me the place, Brother?'

He hesitated. 'The church has been reconsecrated, but I do not believe it is fitting to relive those events before the altar itself.'

'Nevertheless, I must ask-'

With reluctant steps he led me through a door in the rood screen, into the choir stalls. I remembered Goodhaps's remark that the monks seemed more upset by the desecration than by Singleton's death.

The choir held two rows of wooden pews, black with age and richly carved, facing each other across a tiled space. Brother Gabriel pointed to the floor. 'That's where the blood was. The trail led in here.' I followed him through to the presbytery, where the high altar stood, covered with a white cloth, before a beautifully carved altar screen decorated with gold leaf. The air was full of incense. He pointed to two ornate silver candlesticks flanking the centre of the altar table, where the paten and chalice would be laid for Mass.

'It was there.'

I believe the Mass should be a simple ceremony in good English, so men can reflect on their relationship with God, rather than be distracted by magnificent surroundings and ornate Latin. Perhaps because of that, or perhaps because of what had happened there, looking at the richly decorated altar in the dim candlelight I had a sudden sense of evil, so strong that I shuddered. Not a sense of some ordinary crime, nor some furtive little sins, but of evil itself in this business. Beside me, the sacrist's face was bleak with sorrow. 'I have been a monk for twenty years,' he said. 'In the darkest, coldest days of winter I have stood watching the altar at Matins, and whatever weight there has been on my soul it has lifted with the first ray of light coming through the east window. It fills one with the promise of light, the promise of God. But now I will never be able to contemplate the altar without that scene coming into my mind. It was the Devil's work.'

'Well, Brother,' I said quietly, 'there was a human perpetrator, and I must find him.' I led the way back to the choir, where I took a seat in one of the pews, indicating Brother Gabriel should sit beside me.

'When you saw this outrage, Brother Sacrist, what did you do?'

'I said we must fetch the prior. But just then the door from the night stairs was thrown open and one of the monks ran in to tell us the commissioner had been found murdered. We all left the church together.'

'And saw the relic was gone?'

'No. That was later. Around eleven I passed the shrine and saw it was empty. But it must have been done at the same time, surely.'

'Perhaps. Now you too would have come in from the night stairs linking the monks' dormitory to the church. Is that door kept locked?'

'Of course. I unlocked it.'

'So whoever desecrated the church would have had to come in by the main door, which is unlocked?'

Yes. It is our principle that servants and visitors as well as monks should be able to enter the church when they please.'

'And you arrived just after five. You are sure?'

'I have been performing the routine for the last eight years.'

'So the intruder was working in semi-darkness, spreading the fowl's blood and – probably – stealing the relic. Both the desecration and Singleton's murder were carried out between a quarter past four, when Bugge met the commissioner, and five, when you entered the church. Whoever it was worked quickly. That implies they knew the layout of the church.'

He gave me a keen look. 'Yes. It does.'

'And townsfolk do not attend Mass at monastery churches. When outsiders attend special festivals or come to pray to the relics, they are not allowed beyond the rood screen?'

'No. Only monks may come into the choir and before the altar.'

'So, only a monk would know these routines and the layout of the church. Or a servant who worked here – like that man peregrinating the church lighting the candles.'

He looked at me seriously. 'Geoffrey Walters is seventy years old and deaf. The church servants have all been here for years. I know them well and none of them could conceivably have done this.'

'That leaves us with one of the monks, then. Abbot Fabian, and your friend the bursar, would have it that an outsider was responsible. I have to disagree.'

'I think an outsider may be possible,' he said hesitantly.

'Go on.'

'On rising some mornings this autumn I have seen lights out on the marsh; my chamber in the dormitory overlooks it. I think the smugglers are active again.'

'The abbot talked of smugglers. But I thought that marsh was dangerous.'

'It is. But there are paths known to the smugglers running by the little island of higher ground, where the ruins of the founders' church stands, out to the river. Boats can be loaded with contraband wool for France. The abbot complains to the town authorities now and again, but they're not interested. Some of the officials no doubt profit from the trade.'

'So someone who knew those paths could have got in and out of the monastery that night?'

'Possibly. The wall down there is in poor shape.'

'Did you mention seeing lights to the abbot?'

'No. As I said, he has given up complaining. I have been too sore in my mind to think clearly, but now-' An eager look came into his face. 'Perhaps that is the answer. Those men are criminals and one sin can lead to another, even to blasphemy-'

'Of course it would suit the community to lay the blame elsewhere.'

He turned to me, his face set. 'Master Shardlake, it may be you see our prayers, our devotion to the relics of the saints, as foolish ceremonies performed by men who live easily while the world outside groans and suffers.'

I inclined my head non-committally.

He spoke with a sudden intentness. 'Our life of prayer and worship is an effort to approach Christ, to come nearer to his light and further from this sinful world. Every prayer, every Mass is an attempt to come closer to him, every statue and ritual and piece of stained glass is a reminder of his glory, a distraction from the world's wickedness.'

'I see you believe so, Brother.'

'I know we live easier than we should, our comfortable clothes and food are not what St Benedict intended. But our purpose is the same.'

'To seek communion with God?'

He turned, looking at me intently. 'It is not easy. People who say it is are wrong. Sinful mankind is full of wicked impulses, planted by the Devil. Do not think monks are immune, sir. Sometimes I believe the more we aspire to approach God, the more the Devil stirs himself to tempt our minds to wickedness. And the more we have to strive against him.'