The Cold Case squad is a crack team of three detectives, a forensic expert and a psychological profiler. Their brief, to reopen the files on unsolved murders. In this season, a psychotic killer is the key to an investigation when a victim who survived is harassed by a copycat assailant; a deathbed confession appears to link the hanging of an East End gangster and the assassination of the jury who found him guilty; the team come up against a wall of Whitehall secrecy when a petty burglar is acquitted of murdering a prominent Home Officer adviser; and DCI Boyd makes terrible mistakes while under pressure to discover the truth behind the disappearance of an 18-year-old girl.