'So the demonstrations, the one I saw and the other one, used up all the stuff from the barrel?'

'They must have. All, or nearly all.'

'Ay. There must have been nearly half a barrelful in that tank, even if it was only partly filled.'

'By March I think Cromwell's enemy was losing patience with the Gristwoods. Perhaps with a better alchemist they could have divined some alternative, perhaps not. But they dared not spread the word beyond a very small circle. So they devised another plan – they decided to try and turn the fact they only had a limited amount of Greek Fire to their advantage. Oh, they have been very clever.'

'So -' Barak raised a hand, frowning – 'they went to the earl and said they had got Greek Fire, said they had made some, and he told the king.'

'Exactly. And they used a chain of contacts to reach him – Bealknap, Marchamount, Lady Honor – that would make the story sound more plausible.'

'Then none of those three need have been involved.'

'None, or some, or all.'

Barak whistled. 'And then they staged the demonstrations, using what was in the barrel. To trick the earl into making a promise to the king that he could never keep.'

'Yes. Perhaps the Gristwoods were told they'd be paid off and could flee England before Cromwell found out that there was no more Greek Fire. They weren't told about the final part of the plan – to kill them and make it appear as though the formula had been stolen and might be given to a foreign power. After Cromwell had got the king excited, and promised him a demonstration.'

'On Thursday.'

'Yes. The unfortunate founder was killed because he knew too much, I'd guess. Also the throwing device was probably in his yard and Cromwell's enemy needed to take it away.'

Barak nodded. 'You were right to go back to the beginning after all.' He frowned. 'If you're right.'

'It's the only reconstruction of events that makes everything fit.'

He stood a few moments, nibbling thoughtfully at his knuckles. I watched him anxiously, frightened he might see some hole in my theory that I had missed. But he only nodded. 'And poor Bathsheba was killed lest Michael Gristwood might have told her something between the sheets. As he had.'

'I suspect they fired Goodwife Gristwood's house with what little of the stuff they had left to show Cromwell it still existed. And as a warning of what it could do; everyone who saw that fire remarked how the house was aflame from end to end in a moment. If there was an enquiry, that would come out. Imagine how the king would react.'

Barak gave me a look of horror. 'But if you're right, there can never be another demonstration. The earl will have to tell the king anyway.'

'Yes, yes. But he can tell him the whole thing was a plot by his enemies, that the king was deceived as well. Cromwell could still turn it to his advantage. If we can find who's behind it, if he can give the king a name.'

Barak ran a hand over his shaven skull. 'Marchamount? But Marchamount may be only a victim.'

'Yes,' I agreed. 'He may.' My enthusiasm started to wane.

Barak looked at me eagerly. 'If we can uncover who the earl's enemy is, they may still have some Greek Fire. Surely they'd keep at least a little back. If that were given to the king, he could set a troop of alchemists to make it and he might have it after all.'

I had forgotten that possibility. Of course they would keep some back. I cursed inwardly, then took a deep breath.

'Why does nobody think of the death and destruction this thing could wreak? You most of all, Barak – you've seen it, you were nearly killed by it! How can you be so disturbed by what was down that well, yet face the death of thousands by fire without a second thought?'

My appeal fell on deaf ears. 'They would be soldiers. Soldiers expect to fight and die for their country.' He looked at me fixedly. 'If it will save my master, he shall have it.'

I said nothing. Fortunately he was too excited to notice the depth of my concern. 'You should write a letter to the earl at once,' he urged. 'I'll take it to Grey. He should know about this.'

I hesitated. 'Very well. It's too late to go to Lincoln's Inn now, but we'll go tomorrow and see what we can find in Marchamount's rooms.'

'If it turns out he's behind it, and we can bring proof, the earl is safe.' He smiled eagerly.

I nodded. But if we find more Greek Fire, I said to myself, Cromwell shall not have it. If I have to, I will prevent Barak from giving it to him.

Chapter Forty-one

DESPITE EVERYTHING, I slept peacefully that night. I woke towards six refreshed, although my back ached when I got up. I changed the bandage on my arm, pleased to see it had almost healed, then for the first time in days I did Guy's exercises, carefully lest I do more harm than good. It was the eighth of June; we had two days left now.

After breakfast Barak and I walked up to Lincoln's Inn, where the lawyers' day was just beginning. A carousing student lay collapsed on the bench where I had met Lady Honor. He sat up and winced at the light; barristers walking past with papers under their arms gave him disapproving scowls. We passed my rooms and headed for Marchamount's chambers.

The two clerks in his outer office were agitated. One was anxiously explaining a case where Marchamount was due to appear that morning to another serjeant. The other clerk was leafing frantically through a pile of papers; he gave a groan and sped across to Marchamount's room, the door of which was open. We followed him in. He glanced up from searching through another pile of papers and gave us a harassed look.

'This room is private. If you're here about one of Serjeant Marchamount's cases, please wait. We have to find the papers for this morning.'

'We're here on Lord Cromwell's orders.' I said. 'To investigate his disappearance. And make a search.' Barak produced his seal. The man looked at it, hesitated, then shook his head in despair. 'The serjeant will be angry, he has private things in here.' The clerk found the paper he was looking for, grasped it and hurried out. Barak shut the door behind him.

'What are we looking for?' he asked.

'I don't know. Anything. We'll search his living quarters after.'

'If he's gone of his own will, he won't have left anything incriminating behind.'

'If he has. Look in those drawers, I'll search the desk.'

It felt strange to be rifling through Marchamount's possessions. A locked drawer roused our hopes but when Barak prised it open we found nothing inside but a genealogical chart. It traced Marchamount's family back two hundred years. Occupations were scribbled under the names; fishmonger, bell-founder, and worst of all 'villein'. Under one name from a hundred years back Marchamount had scrawled 'This man was of Norman descent!'

Barak laughed. 'How he lusted after that title.'

'Ay. He was always a vain man. Come, let's try his living quarters.'

But there was nothing there either, only clothes, more legal papers and some money, which we left. We quizzed the clerks but all they could tell us was that they had come in to work the day before to find Marchamount gone, with no message and a hundred jobs waiting. Defeated, we left and crossed the courtyard to my chambers.

'I'd hoped there would be something,' Barak said.

I shook my head. 'The people involved in this wouldn't leave evidence of Greek Fire in their homes. Even the Gristwoods kept that apparatus out at Lothbury.'

'They kept the formula at home.'

'And look what happened to them. No, everything's hidden away somewhere.'

'But where, if not in a house?'

I stopped dead. 'What about a warehouse?'

'That's possible. But there are dozens along the river bank.'