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.
as Joe Dennison
as Marline Miller
as Insp. McClaren
as Thompson Blake
as Yeo
as Hunziger
as Sgt. Smith
as Lascelles
as Dr. Eric Miller
as Sir Stafford Beach
as Hoxie
as Castle
as Mickey Sweeney (uncredited)
