None of those people, however, was named Jesse. None of them sounded even remotely like him. When David was through, he looked up at me hopefully.

‘Maybe the ghost belongs to that Chinese launderer,’ he said. ‘The one who was shot because he didn’t wash that dandy’s shirts fine enough.’

I shook my head. ‘No. Our ghost isn’t Chinese.’

‘Oh.’ David consulted the book again. ‘How about this guy? The guy who was killed by his slaves?’

‘I don’t think so,’ I said. ‘He was only five feet tall.’

‘Well, what about this guy? This Dane who they caught cheating at cards, and blew away?’

‘He’s not Danish,’ I said, with a sigh.

David pursed his lips. ‘Well, what was he, then? This ghost?’

I shook my head. ‘I don’t know. At least part Spanish. And . . .’ I didn’t want to go into it right there in my room, where Jesse might overhear. You know, about his liquid eyes and long brown fingers and all that.

I mean, I didn’t want him to think that I liked him, or anything.

Then I remembered the handkerchief. It had been gone when I’d woken up the next morning, after I’d washed my blood out of it, but I still remembered the initials. MDS. I told them to David. ‘Do those letters mean anything to you?’

He looked thoughtful for a minute. Then he closed Colonel Clemmings’s book, and picked up another one. This one was even older and dustier. It was so old, the title had rubbed off the spine. But when David opened it, I saw by the title page that it was called Life in Northern California, 1800–1850.

David scanned the index in the back, and then went, ‘Ah ha.’

‘Ah ha what?’ I asked.

‘Ah ha, I thought so,’ David said. He flipped to a page towards the end. ‘Here,’ he said. ‘I knew it. There’s a picture of her.’ He handed me the book, and I saw a page with a layer of tissue over it.

‘What’s this?’ I said. ‘There’s Kleenex in this book.’

‘It isn’t Kleenex. It’s tissue. They used to put that over pictures in books to protect them. Lift it up.’

I lifted up the tissue. Underneath it was a black and white copy on glossy paper of a painting. The painting was a portrait of a woman. Underneath the woman’s portrait were the words Maria de Silva Diego, 1830–1916.

My jaw dropped. MDS! Maria de Silva!

She looked like the type who would have a handkerchief like that tucked up her sleeve. She was dressed in a frilly white thing – at least, it looked white in the black and white picture – with her shiny black hair all ringleted on either side of her head, and a big old expensive-looking jewel hanging from a gold chain round her long neck. A beautiful, proud-looking woman, she stared out of the frame of the portrait with an expression you just had to call . . . well, contemptuous.