Felix Castor is a freelance exorcist, and London is his stamping ground. At a time when the supernatural world is in upheaval and spilling over into the mundane reality of the living, his skills have never been more in demand. A good exorcist can charge what he likes - and enjoy a hell of a life-style - but there's a risk: sooner or later he's going to take on a spirit that's too strong for him.