Probationary Constable Peter Grant dreams of being a detective in London's Metropolitan Police. After taking a statement from an eyewitness who happens to be a ghost, Peter comes to the attention of Detective Chief Inspector Thomas Nightingale, who investigates crimes involving magic and other manifestations of the uncanny. Suddenly, as a wave of brutal and bizarre murders engulfs the city, Peter is plunged into a world where gods and goddesses mingle with mortals and a long-dead evil is making a comeback on a rising tide of magic.