“You don’t think the police will arrest you, do you?” Gwen said. “They can’t. Not really.”

I pulled my coat tightly around me to protect me from the wind whistling up Camden High Street. Suddenly things came into focus.

“I don’t know,” I said. “I’m not sure if it all fits together. If suddenly I was found dead and it looked as if I’d killed myself, it would be good enough. A grief-stricken widow, a guilty murderer who felt the net closing over her and couldn’t take the pressure anymore. They would be able to close the files on three cases at the same time. If the pieces didn’t quite fit, if it didn’t make complete sense, well, life’s messy, isn’t it? But it would be good enough for the police.”

“Ellie,” said Gwen, horrified, “you mustn’t say that.”

I saw a taxi and raised my arm to hail it. “But if anything happens to me,” I said, “you’ll remember I said it, won’t you?”

I WENT TO bed exhausted, but my nerves were jangling, my mind racing and I knew that sleep was impossible. I tried every trick I could think of to make my brain forget about trying to go to sleep so that it could just go to sleep. I relaxed, I concentrated, I mimicked a supposedly sleep-like regular breathing, eyes closed. I opened them, stared into the darkness and said to myself, That’s what blind people see. I tried to think of something boring, I tried to think of something interesting. I began to wonder how I had ever managed to fall asleep in the past. How can you manage an action that isn’t an action, but instead just a letting-go? I became obsessed with the idea that you can never observe yourself going to sleep, in the same way—I supposed—that you can never experience yourself dying. So I began to think that there must be an earlier falling-asleep you do before you fall asleep, like the premed before an operation, so that you don’t observe yourself falling asleep. But you’re not conscious of that either, so that must be preceded by another, and another, so that actually it’s impossible ever to fall asleep.

As a deranged way of trying to tire myself out and force myself into unconsciousness, I went for a journey in my head, as if thinking about something was as tiring as doing it. I walked out of the house, turned left, then left again and went down to the canal, past Camden Lock through Primrose Hill, then out into Regent’s Park, along Euston Road and back through Somers Town, Camden Town and toward home. It was like a feverish dream, except that I was awake and in control of it.