After a disciplinary incident Rebus is sent on a re-training course. There he falls in with McCulloch and Grey, two detectives involved in a range of corrupt practices, including the fire-bombing of a witness' home. Meanwhile Clarke is investigating the murder of an art dealer in the city. As the cases become entwined, it is revealed Rebus has been working a sting operation against McCulloch and Grey, while the witness takes a grisly revenge.
