The incident I have to describe happened at my thirtieth birthday dinner. I want to set the scene carefully. Our father had died nine months earlier. Cancer. He had, in the months of his dying, made — my mother always insisted — a concerted effort to bring Harper and me closer. He had sat us down at his hospice bed and he had asked us to look after each other. He had said, to both of us, "you are sisters, and I am leaving this earth and I need to know you will be sisters after I am gone." Harper cried. I cried. She took my hand. I took hers. We walked out of the hospice together, and for three weeks afterward, Harper called me every other day. And I believed, genuinely, that the thing my father had asked for was finally happening. My thirtieth birthday was the first family gathering after his death. I had planned it. I had reserved a private room at a restaurant in our hometown. I had invited fourteen people. Harper came with a man I had not known she was dating, a cardiologist named Nate, and she was, for the first hour, the warmest version of herself I had ever encountered. And then the toasts started.