When the decomposed body of a young woman is found near some railway tracks just outside Bristol one hot May morning, all indications are that she committed suicide. That's how the police want it too — all neatly squared away. But DI Jack Caffery is not so sure. He is on the trail of someone predatory, someone who hides in the shadows and can slip into houses unseen. And for the first time in a very long time, he feels scared.

Police diver Flea Marley is working alongside Caffery. With the traumas of her past safely behind her, she's beginning to wonder whether her relationship with Caffery could go beyond the professional. And then she makes a discovery that changes everything. Not only is it far too close to home for comfort, but it's so horrifying that she knows nothing will ever be the same again. And this time, no one — not even Caffery — can help her. . . .