American racketeer Jimmie Dean travels to England, where he assumes the identity of a Canadian whom he has been falsely accused of murdering. Jimmie is then forced to join the British army in the dead man's place. He falls in love with the Canadian's childhood playmate, Sally Briggs, and becomes a hero after saving an isolated English colony in China.
While filling in for injured supersleuth Bulldog Drummond (Atholl Fleming), world-class cricket player Jack Pennington (Jack Hulbert) attempts to foil a criminal mastermind's (Ralph Richardson) impending heist that's targeting a valuable jewel necklace held within the British Museum. This comedic 1930s mystery features daring rescues, intense fistfights and an exciting edge-of-your seat finale aboard a runaway train.