It had been fifty years since it was occupied, you could tell that. The lawn and the formal beds had reverted to brambles, stinging nettles, toadflax, and cow parsley—I learned those names later in case you’re wondering—and the house was a weathered gray color, its large sash windows boarded shut. I’d been expecting something Gothic but this was more like a Regency terrace that had escaped to the countryside and had shot out in all directions before some cruel architect could round it up and pen it back into its original narrow frontage. It was abandoned but not derelict. I could see the guttering was clear, and there were patches of the roof that had clearly been retiled.

Toby came whirring past, yapped a couple of times to get my attention, and then headed into a patch of overgrown woods to the left of the school. Clearly he was a country dog at heart. Nightingale arrived soon after.

“I expected it to have been redeveloped,” I said.

“As what?” asked Nightingale.

“I don’t know. Country hotel and conference center, health spa, celebrity rehab clinic?”

“No,” said Nightingale after I’d explained what a celebrity rehab clinic was. “The Folly still owns the whole estate, and the rents from the farms pay for the maintenance.”

“Why wasn’t it sold off?”

“There was a lot of confusion after the war,” said Nightingale. “By the time it was all sorted out, I was the only person left with any kind of official standing. Selling off the school on my own recognizance seemed … presumptuous.”

“You thought the school might reopen?”

Nightingale winced. “I was trying not to think about the school.”

“The land must be worth a packet now,” I said.

“Do you think it would be improved by becoming a celebrity rehab center?”

I had to admit that this was unlikely. I pointed to the main doors, firmly boarded up and secured with a heavy-duty padlock. “Do you have keys for that?”

Nightingale grinned. “This is where you watch and learn.”

We walked to a spot on the left of the stairs up to the main doors where, hidden by the long grass, a narrow flight of steps led down to a thick oak door that was, I noticed, free of any boarding or chains. It also lacked any visible door handles.

“Behold,” said Nightingale. “The night gate. This was originally built so that the footmen could go straight from their quarters and hop onto the back of their master’s carriage before he could get down the stairs.”

“How very eighteenth-century,” I said.

“Quite,” said Nightingale. “But in my school days we used it for something else.” He placed his palm on the door about where you’d expect the lock to be and muttered something Latin under his breath. There was a click, followed by a scraping sound. Nightingale pushed and the door swung inward.