‘Perhaps. We may be able to help there.’ I paused. ‘The liquid that was to be put in the tank? Did you see anything of that?’
Harper shook his head. ‘Michael said it was a secret, it was better I didn’t know. They did some tests in Master Leighton’s yard. They leased the whole yard from him and wouldn’t let him near. It has a high wall; he keeps lead pipes there for work on the conduits.’
I wondered what Harper’s relationship had been with Gristwood, who was, after all, his stepfather. I guessed it had not been one of affection, but that the nature of his employment made him useful.
‘What was this apparatus like?’ I asked.
He shrugged. ‘Complicated. A big watertight tank with a pump attached and a pipe leading off. It took weeks to make, then Master Leighton said I’d have to have another try—the pipe was too broad.’
‘When did the brothers first employ you?’
‘November. It took till January to get the apparatus right.’
Two months before they went to Cromwell. ‘Are you sure?’
‘Yes.’
‘And where was it kept? In Master Leighton’s yard?’
‘I believe so. They paid him well for its use.’
Goodwife Gristwood laughed mirthlessly. ‘Did Master Leighton get his money?’
‘Ay, Mother, he did. He insisted on payment in advance.’
She frowned. ‘Then where did Michael get the money? Neither he nor Sepultus had any.’
‘Perhaps someone else paid,’ I suggested.
‘They’d have had to,’ the goodwife answered bitterly. ‘I spent fifteen years dealing with Michael’s mad schemes. Sometimes I had hardly any bread for the table. And it’s all ended with him dead and David in danger.’ She looked at her son with a tenderness that softened her face.
‘I can make sure you are both kept safe,’ I said. ‘But I would like to speak to Master Leighton.’ I looked at David Harper. ‘Have you told him I was coming?’
‘No, sir. We thought it better not.’
‘Will he be at his foundry?’
‘Ay, he has a new contract to repair the Fleet Street conduit. He said last Friday he’d have some casting for me. Pleased with himself, he was.’
‘Can you take us there?’
‘And will that be the end of this business?’ Goodwife Gristwood asked.
‘You need be involved no further, madam.’
She nodded at her son. He rose and led the way outside. His mother scuttled after him.
We walked up the lane, further into Lothbury. Through open doors we saw sweat-soaked founders, stripped to the waist, labouring over their fires. People looked out at us curiously as we passed by. At the bottom of a winding lane David stopped before a corner house, larger than most, with a workshop next to it and a high wall beside that.
‘If there were sounds and signs of fire,’ Barak muttered to me, ‘they wouldn’t attract attention here.’
‘No. This was a clever place to choose.’
David knocked at the door of the house. It was shuttered, as were the windows of the workshop. Harper tried the workshop doors too, but they were locked.
‘Master Leighton,’ he called. ‘Master Leighton, it’s David.’ He turned to us apologetically. ‘Many founders grow deaf in their later years. But it’s odd his furnace isn’t lit.’
I had a sense of foreboding. ‘When did you last see him?’
‘Friday, sir, when he told me about his new contract.’
Barak looked at the lock. ‘I could have that open.’
‘No,’ Harper said. ‘I know who has a key. Everyone has a neighbour’s key in case of fire. Wait here.’ He went off down the lane. All around us the banging and clanging resounded in our ears. Goodwife Gristwood began twisting her hands together nervously.
Her son reappeared, a large key in his hands. He unlocked the door and we entered the yard. It was indeed a good place for Michael and Sepultus to have chosen; the high wall enclosed it on three sides and the windowless rear of the adjacent house occupied the fourth. There was a pile of pipes and valves, for Leighton’s work on the conduits, no doubt. Blackened patches all over the walls caught my eye, like the ones I had seen in the Gristwoods’ yard only larger.
Goodwife Gristwood and her son were standing nervously by the gate. I gave David Harper a reassuring smile - he looked as though he might run off any minute.
‘Master Harper,’ I said, ‘tell me: does anything unusual strike you about this yard?’
He looked around. ‘Only that it’s been given a good clean recently.’
I nodded. ‘That’s what I thought. It’s spotless.’
‘Why would anyone want to keep a founder’s yard spotless?’ Barak asked.
‘To hide all traces of what had been here.’ I bent close to him and whispered, ‘I think someone has removed the apparatus, and all traces of Greek Fire as well.’
‘Leighton?’
‘Possibly. Come, I think we should have a look in the house.’