Bulman, Willis and Doran are undercover at the docks trying to identify the ringleaders in a series of bicycle thefts. Back at the office, Rainbow is displeased with their methods. After an accident on the quay, Bulman starts to get romantic ideas about the lady doctor.

When Bulman successfully infiltrates a gang of villains, it isn't long before he finds himself on the run from the police — and desperately in need of the assistance of his undercover colleagues.

When counterfeit Deutschmarks flood Germany and the officers try to establish a connection in England, they find themselves facing violent and ruthless opposition from a murderous gang.

When a successful businessman begins receiving blackmail threats, the squad expect a straightforward case. However, they discover far more than they bargained for and learn that people in high places prove to be bad losers.

Bulman's dedication to duty is so inense that he tries to arrest Carmos, a psychopathic killer, during his wedding, The squad must use all their ingenuity to extricate him from the villain's clutches — Bulman is wounded and in danger of dying.