One must either reach out and discover whether the heart can still respond, or find the courage to let go.… When Daniel first met Emily, he had been struck by the way she laughed. It was not a particularly loud or graceful laugh. Sometimes she laughed at the wrong moment, sometimes at things nobody else found amusing. But there was something disarming about it, something that made him feel that the world was a little less complicated than he had always imagined. They met at a small bookstore café in London. Daniel was thirty-nine, an architect who spent most of his days designing buildings for people he would never meet. Emily was thirty-six, a publishing editor who believed that every good story contained at least one person who was desperately trying to hide the truth from themselves. For the first two years, they were inseparable. They traveled together, cooked together, and developed the kind of private language that couples create...