A freelance exorcist is drawn into a dangerous conspiracy when a client's death reveals a hidden supernatural world. Felix Castor makes a living by banishing ghosts and other spectral nuisances, a job that keeps him on the fringes of society. When a routine case turns deadly, he uncovers a plot involving powerful entities and a secret war that threatens the fragile peace between the living and the dead. He must navigate a treacherous landscape of ancient magic and modern deception to uncover the truth before he becomes the next victim.

The Felix Castor series, beginning with 'The Devil You Know,' is recognized for its gritty, noir-infused take on urban fantasy. Critics often praise Mike Carey's sharp prose and the compelling, world-weary protagonist. The series is noted for its intricate plotting and its exploration of complex moral themes within a supernatural framework. Readers generally appreciate the mature tone and the detailed world-building that sets it apart from more conventional fantasy offerings.