“Yep.” It was all of thirty feet high, and the Roman section itself maybe ten feet. The Roman brickwork was neat rows interspersed with red tiles that might have come from my father’s house. The medieval structure above it was much rougher. “If I didn’t know better I’d have said that the Roman stuff was Victorian, or later,” I said. “It’s as if the whole wall has been turned upside down.”

Linda asked, “Civilization really did fall here, didn’t it?”

“It really did.”

“I wonder if she came here. That great-grandmother of yours. Regina.”

“. . . And I wonder if she knew that it would all disappear, as if a small nuclear bomb had been dropped on the city.”

The third voice made us both jump. I turned to see a bulky, somewhat shambling figure dressed in a coat that looked even heavier than my duffel. Linda flinched away from him, and I felt the tentative mood between us evaporate.

“Peter. What are you doing here?”

Peter McLachlan came around the bench and sat down, with me between him and Linda. “You mentioned doing the walk.” So I had, in an email. “I thought you’d end up here. I waited.”

“How long?”

He checked his watch. “Only about three hours.”

“Three hours?”

I could see Linda’s expression. “Listen, George, it’s been good, but I think—”

“No. Wait, I’m sorry.” I introduced them quickly. “Peter, why did you want to see me?”

“To thank you. And tell you I’m going to be away for a while. I’m off to the States.”

“Visiting the Slan(t)ers?” Linda caught my eye again; I pursed my lips. Don’t ask.

“I feel the need to catch up. Be refreshed.”

“Refreshed with what?”

He shrugged. “The energy. The belief. That’s why I want to thank you. Somehow you have shaken me out of my rut. Your bit of mystery with your sister. Layers upon layers . . . That and Kuiper, of course.” He leaned past me and thrust his face toward Linda. “Of course you know about the Kuiper Anomaly. Have you seen the latest developments?” He produced his handheld and started thumbing at its tiny controls, and Web pages flashed over its jewel-like screen.

Linda plucked my sleeve. “This guy is seriously weird,” she whispered.

“He’s an old school friend. He helped my dad. And—”

“Oh, come on. Your dad’s buried. He’s followed you to London. And all this spooky stuff—what does it have to do with you and your sister?”

“I don’t know.”

“Look, George, I changed my mind. It’s as if the people around you are parts of your personality. Your family was the clingy, oppressive, Catholic part, and you need to get away from all that, not indulge it. And this guy, he’s like your—”

“My anus.”