The Four Men of the title are British WWI veterans who decide to work secretly against enemies of the country. They aren't above a bit of murder or sabotage to serve their ends, but they consider themselves to be true patriots.

A young woman finds herself as the intended victim of a murder plot on a transatlantic flight from London to New York.

Dr. Laurence, a once-respectable scientist, begins to research the origin of the mind and the soul. The science community rejects him, and he risks losing everything for which he has worked. He begins to use his discoveries to save his research and further his own causes, thereby becoming ... a mad scientist, almost unstoppable.

Jim Smiley has a frog that can jump further than anyone else's frog, and Jim becomes obsessed with entering the frog in all of the local jumping-frog contests, not realizing that his obsession is about to cost him his marriage.

Scotland Yard Inspector George Gideon starts his day off on the wrong foot when he gets a traffic-violation ticket from a young police officer. From there, his 'typical day" consists in learning that one of his most-trusted detectives has accepted bribes; hunts an escaped maniac who has murdered a girl; tracks a young girl suspected of involvement in a payroll robbery and then helps break up a bank robbery.

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.