Ken and Harry call in on the spur of the moment to check Don Jakes, the security guard that they have employed at a safety deposit company, Unicorn Deposit Ltd. While searching for him, they walk into the vault. The door swings shut and an unknown person locks it behind them, trapping them inside. Ken and Harry see that the vault has been ransacked and that the cable for the security camera has been cut. They realise that they will probably be trapped all weekend. They think that Don might have been attacked, which is why he can't rescue them.

Don leaves the vault and meets his Scottish girlfriend, Billie. They have stolen the contents of the vault and are planning to run away together to Argentina.

Ken had arranged to meet Laura, who is getting obscene phone calls at home. When he doesn't turn up and she can't contact either him or Harry, she gets very worried. She and Rocky start to investigate.

Don's wife, Jeanette, becomes suspicious when she sees Don with Billie, who is her hairdr