“That’s just a nickname,” said Nightingale. “It’s a booby trap. I suppose you could call it a magical land mine. I haven’t seen one of those since 1946.”

“Shouldn’t I know about these things?” I said.

“The list of things you need to know about, Peter, is extraordinarily long,” said Nightingale. “And I have no doubt that even you will eventually cover them all. But there’s no point learning about demon traps until you’ve studied basic enchantment.” He held up his cane to show that the silver top was blackened and melted in places. Enchantment, I knew from my reading, was the process by which inanimate objects are imbued with magical qualities.

Nightingale examined the cane ruefully. “Although I may be demonstrating how it’s done in the next couple of months,” he said. “That being the case, we may as well provide you with a training staff while we’re at it.”

“The demon trap,” I said. “Did you recognize the signature?”

“The signare?” he asked. “Not the individual, but I think I know who trained the vicious little so-and-so.”

“Geoffrey Wheatcroft?” I asked.

“The very same.”

“Could he have been the original magician?”

“That’s something we’re going to have to look into,” said Nightingale.

“He’d have to have schlepped back and forth between here and Oxford,” I said. “If he was doing that, then he must have had an assistant.”

“One of his pupils?”

“Who might have gone on to be our new magician,” I said.

“This is all terribly speculative,” he said. “We need to find the assistant.”

“We should start interviewing all the people who had contact with Geoffrey Wheatcroft or Jason Dunlop.”

There was an ironic cheer as one of the portable floodlights was restarted.

“That’s an ambitious list of suspects,” said Nightingale.

“Then we start with the ones who knew both of them,” I said. “We can do it under the pretext of investigating Jason Dunlop’s murder.”

“First,” said Nightingale, “I want you to go and secure Smith’s office.”

“You don’t need me here then?” I asked.

“I’d rather you didn’t see what’s in there,” said Nightingale.

For a moment I thought I’d misheard him. “What is in there?” I asked.

“Some very beastly things,” said Nightingale. “Dr. Walid has people coming in who’ve handled this sort of situation before.”

“What sort of situation?” I said. “What sort of people?”

“Forensic pathologists,” he said. “People who’ve worked in Bosnia, Rwanda—that sort of situation.”

“Are we talking mass graves here?”

“Among other things,” he said.

“Shouldn’t I—”

“No,” said Nightingale. “There’s nothing in there that it would profit you to see. Trust me in this, Peter, as master to apprentice, as a man who’s sworn to protect and nurture you. I don’t want you going in there.”

And I thought—do I really want to go in there?