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 investigates when an unidentified body is found in the grounds of a local Edinburgh hotel which is due to play host to the World Trade Summit. When another body is found in the grounds of Edinburgh castle, Special Branch intervene and warn Rebus off the case.

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.