DS Catrin Price receives a series of cryptic messages from an old school friend. When Cat visits him at his isolated house in the depths of the Brecon Beacons she discovers that his beloved daughter is missing. But she's not the only one. Other girls in the area have been disappearing, and when one of them is found dead in an abandoned mine shaft, Cat fears the worst.

Ignoring instructions to leave the case well alone, she embarks on a desperate hunt that will take her to one of London's most notorious drug gangs and into the darkest corners of her mind. Cat will stop at nothing to uncover the truth, but there are people who will do anything to keep it hidden - and they are watching her every move.