A debutante's abduction with links to the Troubles in Northern Ireland gives the UCOS squad another complex cold case to solve, as the detective drama continues. When the former leader of an Irish Republican group comes forward with information regarding the abduction and subsequent disappearance of an 18-year-old woman in 1983, the team reopens the case. The reformed dissident claims the rebels used the kidnapping to promote their profile, but his subsequent reinvention as a politician and man of peace leaves the team suspicious of his motives. They also investigate whether the victim's arms manufacturing father's activities could have made her a target. Sian Phillips and Annette Crosbie guest star tonight, with Amanda Redman and James Bolam.