James Kennedy, a hard-driving American who is the executive officer in a London chemical firm, decides to use his business acumen in dealing with the international criminals who have kidnaped his son. Ignoring the assistance of Scotland Yard's Inspector Hazelrigg, Kennedy sends twice the amount of money demanded in the ransom note in the expectation that the abductors will quarrel over the division of the money. The plan works, for one of the gang is found murdered, and clues on the body lead Kennedy and the police to a house in Hampstead where the ringleader, Feist, is hiding with Kennedy's son. Hazelrigg agrees to allow Kennedy to go in alone, but says that he will wait only 3 minutes before following. As Kennedy approaches, Feist attacks; but Kennedy fights him off with a homemade flamethrower and then locks himself in a room with his son as the police break in and apprehend the gang.