In 2015 Sheryl Sandberg's husband, Dave Goldberg, died suddenly at the age of forty-eight. Sandberg and her two young children were devastated, and she was certain that their lives would never have real joy or meaning again. Just weeks later, Sandberg was talking with a friend about the first father-child activity without a father. They came up with a plan for someone to fill in. "But I want Dave," she cried. Her friend put his arm around her and said, "Option A is not available. So...