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.
Dennis O'Keefe
Margaret Sheridan
Philip Friend
Alan Wheatley
Francis de Wolff
Eric Berry
Gudrun Ure
Seymour Green
Paul Hardtmuth
Colin Tapley
Michael Balfour
Cyril Chamberlain