Six-year-old Emma vanished into the thick San Francisco fog. Or into the heaving Pacific. Or somewhere just beyond: to a parking lot, a stranger's van, or a road with traffic flashing by. Devastated by guilt and haunted by her fears about becoming a stepmother, Abby refuses to believe that Emma is dead. And so she searches for clues about what happened that morning and cannot stop the flood of memories reaching from her own childhood to illuminate that irreversible moment on the beach.