"Then She Was Gone" is a psychological thriller novel by Lisa Jewell that revolves around the mysterious disappearance of a teenage girl named Ellie Mack. The story unfolds years later when her mother, Laurel, struggles to cope with the loss and begins to rebuild her life, only to encounter a new relationship that brings unexpected revelations. As Laurel delves deeper into her new partner's life, she uncovers unsettling connections to her daughter's past. The narrative explores themes of grief, love, and the complexities of family dynamics, ultimately leading to shocking truths about what happened to Ellie.