A hard-nosed career officer in the male-dominated world of British policing, DCI Claire Pierce of North Yorkshire Police heads Northern England's underfunded and understaffed Ritual Crime Unit. Injured in the line of duty, Pierce returns to work to find her new Detective Inspector has brought in a self-proclaimed necromancer to question the victim of a murder, there's a coven of druids outside protesting the sale of their sacred site, and an old iron lantern in the evidence room has just sent out a signal.

Pierce is going to have to hit the ground running. A suspected ritual murder and a string of puzzling artefact thefts initially seem unconnected, but signs point to something bigger: buried skulls possessed by evil spirits start turning up, and they may only be the beginning. Someone is planning something big, and the consequences if they succeed could be catastrophic. With a rebellious second-in-command, an inexperienced team, and a boss who only cares about potential bad publicity, Pierce has to make the connections and stop the ritual before it's too late...