Someone is stealing priceless paintings from the great museums of the world and replacing them with nearly flawless forgeries. Leonardo da Vinci's "Madonna and Child" is being shipped to London's Tate Gallery for a special exhibition, and Paul Mitchell is assigned to protect it. Upon the painting's arrival, Paul realizes it has been switched. Eager to collect the museum's $50,000 reward, he teams up with Mary Mason, a Tate employee, to recover the original.
While in London trying to nab several fugitives who stole a million dollars from a U.S. Treasury vault, American federal agent Dennison (Dennis O'Keefe) assists Scotland Yard Insp. McClaren (Philip Friend) in his search for a missing atomic scientist (Paul Hardtmuth). The detective duo discovers that the key to solving both cases may rest with the scientist's daughter (Margaret Sheridan) and her fascinating diamond.
A woman conspires to steal her stepdaughter's inheritance following the mysterious death of her millionaire husband.
