On a cold December night in Cornwall, nanny Karen Peterson disappears with three-year-old Sophie Flynn. The next day, the child's body is found on the banks of Penhale Wood. A year later, Sophie's mother, Iris Flynn, appears on the doorstep of investigating officer Rob McIntyre, determined to make him reopen the case. McIntyre has his own personal demons, but Iris hijacks his life in order to find the person responsible for her daughter's death. Following the slimmest of leads, they are soon confronting ghosts from the past and a chameleon-like killer who will do anything to stay hidden.