Brian Lane's future at UCOS is threatened after he assaults one of the Met's most successful officers at a retirement function in an act of revenge for his own retirement from the force. With a team member down, it's business as usual for Sandra, Steve and Gerry after the discovery of a mysterious gun in the Thames re-opens the unsolved 1998 murder of a playboy shipping heir and a killing that leads the team to the Rock of Gibraltar. In the UK, Brian finds life without police work unbearable and defies his superiors once again by flying out to Gibraltar.

New evidence frees a getawy car driver who was jailed 16 years go for killig his wife. Gerry is furious, he worked the original investigation and feels his reputation is on thel ine. Brian, meanwhile, faces the possibility that his career is over