Fred Martin, a taxi driver who is a reformed convict, is used by the police to go undercover in order to help catch a gang of safe robbers. However things start to go wrong when the police stake out the wrong bank and Fred finds himself alone with the crooks.
The host of a radio crime show finds himself mixed up with real gangsters after he re-creates a notorious murder on the air. He uses his knowledge of criminology to foil the gang's wicked scheme.
British diamond smugglers use the radiowoman (Phyllis Kirk) from a freighter docked on the Thames to unwittingly "mule" their swag, hidden in cigarettes, past customs, not knowing that she has befriended an Inspector for the Thames River Patrol.
A gang of four would-be robbers plans to steal a fortune in currency hidden aboard the "Flying Scotsman" in a railroad stateroom by cutting through the wall of the adjacent stateroom, but find themselves up against numerous unexpected drawbacks, including interference by their fellow passengers.
