At the time, I had assumed that Mark had committed the last two murders. There had been a shot, then a thud, then the opening and closing of a door. But a few seconds later, Mark had himself been killed. And what about the leaves that I had seen lying next to his body? How had they gotten there?

I thought back to the other murders. Rory first. We had all been on the island and we had all separated. Any one of us could have attacked him and, immediately afterward, left the chocolate on the bed for Sylvie to find. That was the night I had seen the face at the window. A face that had appeared and disappeared—impossibly—in seconds. And then we had found Janet. I remembered her lying in her bed, stabbed by a model of the Eiffel Tower. Her room had been shabby. There had been a tear in the canopy . . . I had noticed it at the time. Why had it caught my eye?

Libby Goldman next. The television show host had been knocked down with a model globe. There was something strange about that, too. Someone must have carried it up to the roof and dropped it on her when she came out of the front door. But now that I thought about it, I hadn’t seen the globe in any of the rooms when we had been searching the house. And that could mean only one thing. It had been on the roof from the very start, waiting for her . . .

Maybe you know how it is when you’ve been given a particularly nasty piece of homework—an impossible equation or a fiendish bit of physics or something. You stare at it and stare at it, but it’s all just ink on paper and you’re about to give up when you notice something and suddenly you realize it’s not so difficult after all. Well, that was what was happening to me now.

I remembered the search party, slowly crisscrossing the island. We had seen security cameras everywhere, and from the day I had arrived, I had felt that I was being watched. There was a security camera in the kitchen. I looked up. It was watching me even now. Were there cameras in other rooms, too?

At the same time, I remembered something Mark had said, when we had found the old photograph of St. Egbert’s. And in that second, as quickly as that, I suddenly knew everything.

“I’ve got it, Tim!” I said.

“So have I, Nick!” Tim cried.

I’d been so wrapped up in my own thoughts that I hadn’t noticed Tim had been thinking, too. Now he was staring at me with the sort of look you see on a fish when it’s spent too much time out of water.

“You know who did it?” I asked.

“Yes.”

“Go on!”