
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)