“You’re being honest. Milena was a complicated woman.” I worried that I’d gone too far. I didn’t want Frances to think I was prodding her into being rude about her friend. “And messy,” I said, standing up and crossing the room to fetch another pile of unsorted papers. “I’d better crack on with this lot.”

“Gwen?”

“Yes.”

“It’s really nice to have you here.”

I tried to smile. “It’s nice to be here.”

AT LUNCHTIME, BETH went upstairs to the kitchen and made us the kind of meal I’ve always imagined women eat after they’ve had their hair done: a light salad of green beans, butter beans and beansprouts, scattered with health-giving seeds and dressed with a lemon vinaigrette, and when we’d finished, I was hungrier than I had been before.

Answering Frances’s questions, I found out more about my life as Gwen: it turned out that she had grown up in Dorset, the youngest of five children, gone to Leeds University and studied math and physics, that she liked gardening and even had an allotment (stop! I commanded myself—you know nothing about allotments), that her father was dead. I felt a growing anxiety as I made up a life on the spot. It would have been much simpler to stick to the facts of my own life—or that of the real Gwen at the very least. Now I had to remember what I had said. Beth didn’t speak but just looked at me. Had I made a mistake? All it would take was for Beth or Frances to be a bit too familiar with Dorset or Leeds or Leytonstone, and who knows what would happen? At the same time, I felt a thrill of pleasure as I concocted a life for myself. I’d always wanted to be the youngest in a large, close family, rather than the eldest in a small, distant one, and now, for a few days, I was. And maybe I’d get an allotment. Why not? Anything is possible when you decide to be someone else.

AT ABOUT FOUR o’clock, when the day outside was thickening toward twilight, Beth answered the phone, then muttered something to Frances.

“Bloody hell,” said Frances. “All right, we’d better go.” She sat lost in thought for a moment, then looked at me as if she had forgotten my existence. “Gwen,” she said, “something’s come up. We’ve got to pop out. Would you mind holding the fort?”