It's been a year since Billie Flanagan--a Berkeley mom with an enviable life--went on a solo hike in Desolation Wilderness and vanished from the trail. Her body was never found, just a shattered cellphone and a solitary hiking boot. Her husband and teenage daughter have been coping with Billie's death the best they can: Jonathan drinks as he works on a loving memoir about his marriage; Olive grows remote, from both her father and her friends at the all-girls school she attends. But then she starts having waking dreams--hallucinations?--in which her very vibrant mother urges the girl to look for her, and Olive begins to believe her mother is still alive and in trouble. Jonathan believes the trauma and anxiety of losing her mother is making Olive ill, until he uncovers a secret that that compels him to consider that Billie may not be dead after all and sends him on his own quest for the truth--about Billie, their marriage, and the things people do in the name of love.