Rebus is forced to attend a training course at police school following a public outburst, with his colleagues unaware that he is actually out to expose two corrupt police officers who have been running a protection racket, and could possibly be linked to the murder of a drug dealer.

Rebus is called to investigate when the naked body of the Moderator Elect of the Church of Scotland is found in a local cruising spot with the body of a naked woman. Forced to deal with ongoing political battles between the church and its ministers, Rebus must solve the case in time for the gathering of the General Assembly.

Rebus finds himself being investigated by an old friend after a murderer walks free on a technicality. Matters are made worse when the suspect and his brother are found dead, and the prosecutor in the case is found to have been paid off to discredit Rebus and his colleagues.