Kytchyn came to a halt by a wall. 'They brought me here, sir,' Kytchyn said. 'There was a barrel standing by the wall, a heavy old wooden barrel.'

'How big?'

'You can see the mark in the dust.'

He lowered the candle and I saw a wide circle in the dust on the stone flags. The barrel had been as large as a wine cask, big enough but not enormous. I nodded and stood up again. Kytchyn held the candle near his chest, making his lined face appear disembodied.

'Had it been opened?' I asked.

'Yes. One of the Augmentations men was there, holding a chisel he'd used to prise the lid off. He looked relieved to see us. Master Gristwood said, "Look in here, Brother Librarian" – I was still brother then – "and tell me if you recognize what's inside. I warn you, though, it stinks." Master Gristwood laughed, but I saw the other Augmentations man cross himself before he lifted the lid for me.'

'And what was inside?' I asked.

'Blackness,' he replied. 'Nothing but blackness, deeper than the blackness of the crypt. And a dreadful smell, like nothing I'd ever known before. Sharp, with a strange sweetness, like something rotting yet lifeless too. It caught my throat and made me cough.'

'That's what I smelt,' Barak said. 'You've caught it well, fellow.'

Kytchyn swallowed. 'I lifted the candle I carried and held it over the barrel. The darkness inside reflected the light. It was so strange I nearly dropped the candle into it.'

Barak laughed. 'God's death, it's as well you didn't.'

'I saw it was a liquid. I touched my finger to it.' Kytchyn shuddered. 'It had a horrible feel, thick and slimy. I told them I'd no idea what it was. Then they pointed to the plaque with St John's name on, that showed it had been there a hundred years. I said there might be some record of it in the library. I tell you, sir, I wanted to get away.' He looked round him fearfully.

'I can understand,' I said. 'So it was dark, black. That explains why one of the names the ancients had was Dark Fire.'

'Dark as the pit of hell. Master Gristwood agreed, ordered his man to seal the barrel up again, then came back to the library with me.'

'Let's go there too,' I said. 'Come, I can see you would like to be out of here.'

'Thank you, yes.'

We made our way back to the church, then out into the sunlight. Kytchyn stood looking at the rubble, tears at the corners of his eyes. In the old days, when a monk or friar entered the cloister he ceased to have a separate legal personality, he died to the world. An act had just gone through parliament restoring their legal status as individuals. In Lincoln's Inn people joked about them being 'restored to life' by Cromwell. But to what life? 'Come, Master Kytchyn,' I said gently, 'the library.'

He led us through the roofless chapter house and I realized we would have to pass across the garden. The children were still playing there; a maid taking in the washing gave us a curious look.

We were halfway across when a door opened and a small man in a fine silk shirt came out. I drew a sharp breath, for I recognized Sir Richard Rich at once. I had been introduced to him at a function at the Inn. 'Shit,' Barak murmured under his breath, then bowed low as Rich came over. I bowed too, as did Kytchyn, whose eyes had widened with fear.

Rich halted before us. There was a puzzled frown on his handsome, delicately pointed features. Piercing grey eyes surveyed us.

'Brother Shardlake,' he said in a tone of amused surprise.

'You remember me, sir?'

'I never forget a hunchback.' His smile reminded me of his reputation for cruelty; it was said he had sometimes operated the rack himself in his days investigating heresy. To my surprise the little girls ran towards him, arms outstretched. 'Daddy, Daddy!' they cried.

'Now, girls, I am busy. Mary, take them indoors.'

The servant gathered the children together. Rich looked after them as they were led away. 'My brood,' he said indulgently. 'My wife says I don't whip them enough. Now then, what are you three doing in my garden? Ah, the former Brother Bernard, is it not? White suits you better than Dominican black.'

'Sir – I – sir-' Poor Kytchyn was tongue-tied.

I spoke up, trying to make my tone as light as Sir Richard's. 'Master Kytchyn is showing us the library. Lord Cromwell said I might see it as a favour.'

Rich inclined his head. 'There are no books left, Brother, my Augmentations men have burned them all.' He smiled mockingly at poor Kytchyn.

'It was the design of the building, my lord,' I said. 'I am thinking of building a library.'

He chuckled. 'You'd be better looking at one with the roof still on. By God's wounds, you must be doing well at Lincoln's Inn. Or does your wealth come from Lord Cromwell? Back in favour, eh?' Rich's penetrating eyes narrowed. 'Well, if the earl says you may look at the library I suppose you may. Watch the crows nesting on the roofbeams don't shit on you. From papist shit to birdshit, eh, Brother?' He smiled again at Kytchyn, who hung his head. Rich's mouth set hard as he turned his eyes to me.

'But ask permission if you wish to walk though my garden again, Shardlake.' Without another word he followed his children indoors. Kytchyn turned and led us rapidly away to a gate in the wall.

'I knew it was a bad idea to come here,' Barak said. 'My master said Rich was to know nothing.'

'We didn't tell him anything,' I said uncomfortably.

'He's curious. Don't look round, but the arsehole's watching us through the window.'

Kytchyn led us through the gate onto a trampled lawn surrounded on three sides by roofless buildings. He pointed. 'The library's there, next to the infirmary.'

We followed him into what must once have been a large, imposing library. Empty shelving covered the walls to a height of two storeys, and the floor was strewn with broken cupboards and torn manuscripts. It saddened me even more than the church had. I looked up to where a few skeletal roofbeams still stood, casting lines of shadow on the floor. A flock of crows took off, cawing. They circled and settled again. Through a glassless window I caught a glimpse of a lawned close with houses beyond. A fountain in the middle was dry. Kytchyn stood looking around miserably.

'So,' I asked quietly, 'when you came here with Master Gristwood, what did you find?'

'He wanted me to look for references to that soldier St John. Any papers of note left by those who died in the hospital were filed away. There were some under St John's name and Master Gristwood took them all. Then the next day he came back and spent a whole afternoon here, looking up any references to Byzantium or Greek Fire.'

'How did you know that was what he was after?'

'He got me to help him, sir. He took some more papers and some books. He never brought them back and soon after all the shelves were cleared, everything burned.' He shook his head. 'Some of the books were very beautiful, sir.'

'Well, it's all done now.'

There was a sudden clatter of wings as the crows took off again. They circled above, cawing noisily. 'What made them do that?' Barak muttered.

'You helped Master Gristwood search for papers. Did you look at any of them?'

'No, sir. I didn't want to know.' He looked at me seriously. His face was covered in sweat; it was hot in there, the sun shining down on us. 'I am not a bold man, sir. All I want is to be left to my prayers.'

'I understand. Do you know what happened to the barrel?'

'Master Gristwood had it taken away on a cart. I don't know where, I didn't ask.' Kytchyn took a deep breath, and lifted his hand to open the collar of his surplice. 'Excuse me, sir, it's so hot-' As he spoke he took a sideways step. From somewhere I heard a faint click.

Kytchyn's gesture saved my life. Suddenly he jerked forward with a high-pitched scream, and to my horror I saw a crossbow bolt embedded in his upper arm, blood welling red over his white surplice. He staggered against the wall, looking at his arm in horror.