Lane's future at UCOS is threatened by a death in custody which emerges from his past. Meanwhile, the discovery of a mysterious gun in the Thames re-opens the unsolved 1998 murder of a playboy shipping heir and leads the team to the Rock of Gibraltar.

The team unlock over three decades of secrets and lies on the Rock of Gibraltar and find the link which solves the murder of a playboy shipping heir from '98 and a young local boy from '82. With both cases solved, they return to England where Lane faces a disciplinary hearing, dragging up a death in custody from his past which threatens his career in UCOS.