Ruth and Simon reluctantly agree to let their young teenage daughter, Heather, go off on a camping holiday in Cornwall with her best friend, Kelly, and her family. While on a vacation of their own, they get the news that both girls have gone missing. Kelly is found alive, but, after several days of searching, Heather's body is discovered inside some old mine workings. Although the police detective leading the investigation harbours suspicions of foul play, the verdict is that the death was accidental.

The emotional strain of Heather's death ruins Ruth and Simon's marriage. After the divorce, Ruth moves from London to Cambridgeshire, where she remarries and has another child - a daughter, Beatrice. But when Beatrice is close to the age Heather was when she died, she too mysteriously disappears ...

Helen Walker (of Harvey's 2008 novel Gone to Ground), one of the officers involved in the investigation, travels to Cornwall to seek connections between Beatrice's disappearance and Heather's death. Will Grayson (also of Gone to Ground), the officer leading the enquiry, is torn between his fears that a recently paroled child-abuser might be responsible and his growing suspicions that someone closer to home might have taken Beatrice. With the stakes impossibly high and time running out, Helen and Will draw closer to their quarry while the truth seems to slip further into the distance.