Whilst Brian faces disciplinary action for a death in custody from his past the rest of the team discover the gun that killed drug-trafficker Christian Highsmith in 1998. The same gun killed a young boy, Danny Bossano, in 1982 in Gibraltar, a port of call for the ships on which Christian allegedly hid the drugs. The UCOS team go to Gibraltar to meet Superintendent Cruz, the local cold case chief, who believes Danny was part of the dope-smuggling gang. The fact that the gun was army issue also leads to the evasive commander Adam Sinclair whilst Sandra quizzes casino owner Harry Truman, who had been a friend of Christian. Gerry and Steve visit Truman's casino but accidentally get locked in a shipping container whilst shipping agent Gordon Fletcher, an associate of Truman, is found dead.