“Why not?” I asked. “I used to make shapes when I was going to sleep when I was a kid, or listening to music. Everyone does it and among billions of people, no matter how unlikely something is, if you repeat the action enough times there’s a result—there’s magic. How else could Newton stumble onto the principle in the first place. They were the wrong girls doing the wrong thing in the wrong place and …”

“And what?” asked Dr. Walid.

“I think they survived the blast at the Café de Paris because they channeled magic, or life energy, or whatever this stuff is, through the forma in their minds. We know that magic can be released at the point of death—hence sacrifices.”

“Hence vampires,” said Nightingale.

“Not vampires,” I said. I’d been studying my Wolfe. “Tactus disvitae, the antilife, is the mark of the vampire. This is more like alcohol or drug dependency; the damage is an unintended consequence, like cirrhosis of the liver or gout.”

“Human beings are not bottles of brandy,” said Nightingale. “And Wolfe always was too keen on categorizing and subcategorizing everything. A rose by any other name and all that. Still—where would she have gone?”

“Most likely the flat on Berwick Street,” I said.

“Back to the nest,” said Nightingale. And I didn’t like the way he said it.

Dr. Walid handed me a couple of painkillers and half a bottle of Diet Pepsi he must have found in the fridge. There was no fizz when I unscrewed the top and it tasted flat when I swallowed the tablets—it must have been in there for ages.

He sat down next to me on the sofa and put his hand on my arm. “If your father really did have a close encounter with Simone at some point in the past we may be able to find evidence of that. So I want you to bring your father to the UCH tomorrow at eleven,” he said and then pointed at Nightingale. “You I want in bed in the next half hour with a hot milk and a sleeping tablet.”

“There’s—” said Nightingale but Dr. Walid didn’t give him a chance to start, let alone finish.

“If you don’t follow my instructions, I swear on my father’s life that I’ll have you both put on medical leave,” he said. “Do you both ken me on this?” We nodded obediently.

“Good,” he said. “I’ll see you tomorrow.”

Later, while we were wrangling hot drinks out of Molly in her kitchen, Nightingale asked me if I thought Dr. Walid actually had the authority to carry out his threat. “I think so,” I said. “He’s down on paper as our OCU’s registered medical adviser. If we had any cells here he’d be the one we called in if our prisoners needed medical attention. Do we have any cells?”

“Not anymore,” said Nightingale. “They were all bricked up after the war.”