Felix Castor is a freelance exorcist, and London is his stamping ground. It may seem like a good ghostbuster can charge what he likes and enjoy a hell of a lifestyle – but there's a risk: Sooner or later he's going to take on a spirit that's too strong for him.
While trying to back out of this ill-conceived career, Castor accepts a seemingly simple ghost-hunting case at a museum in the shadowy heart of London – just to pay the bills, you understand.
But what should have been a perfectly straightforward exorcism is rapidly turning into the Who Can Kill Castor First Show, with demons and ghosts all keen to claim the big prize. That's OK: Castor knows how to deal with the dead. It's the living who piss him off.