In this twisty, mind-bending thriller from the bestselling author of Behind Her Eyes, Emma Averill worries that her sudden insomnia is a sign that she's slowly going insane-like the mother she's worked so hard to leave in her past. Emma Averill loves her life-her high-powered legal career, her two beautiful children, and her wonderful stay-at-home husband- but it wasn't always so perfect. When she was just five-years-old, Emma and her older sister went into foster care because of a deeply disturbing incident with their mother. Her sister can remember a time when their mother was loving and 'normal', but Emma can only remember her as one thing, a monster. And, that monster emerged right around their mother's fortieth birthday, the same age Emma is approaching now. Emma desperately wants to keep her dream life separate from her past, so she's always hidden her childhood trauma. But, then she stops being able to sleep, and now she's losing time, during the day, also one of the first symptoms her mother showed. Is the madness in her blood, just as her mother predicted? Could she end up hurting her family in her foggy, half-awake state? Or is there another explanation for the strange things that keep happening around her? Emma must unravel the dark strands of her past to protect the people she loves... or risk ending up just like her mother.