
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.