Just after lunch on a Tuesday in April, nine feet under water, police diver Flea Marley—haunted by the recent mysterious death of her parents—closes her gloved fingers around a human hand. The fact that there's no body attached is disturbing enough. Yet more disturbing is the discovery, a day later, of the matching hand. Both have been recently amputated, and the indications are that the victim was still alive when they were removed.

Leading the case is DI Jack Caffery, relocated from London to Bristol in an effort to distance himself from the memories of his brother's childhood kidnapping and murder. Unable to shake his personal demons, Caffery throws himself into his work, following a trail that seems to lead toward black-magic rituals and a string of missing drug addicts. Flea Marley pursues the case as well, turning to an old family friend who is well-versed in witchcraft and ritual. She suspects he knows more than he'll admit, including information about her father's own links to forms of witchcraft. It isn't until their suspicions force Caffery and Flea to work together that things start to click into terrifying place, and they find themselves confronting not only a sadistic killer but the ghosts of their own pasts.