When the decomposed body of a young woman is found near railway tracks just outside Bristol one morning, all indications are that she's committed suicide. That's how the police want it too; all neatly squared and tidied 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 their relationship could go beyond the professional. But then she finds something that changes everything. Not only is it far too close to home for comfort - it's so horrifying that she knows that nothing will ever be the same again.

And this time, no one - not even Caffery - can help her ...