The Master Key is set in 1938. Nazi spies, led by the mysterious "Master Key", kidnap Professor Henderson in order to acquire his "Orotron machine" which is capable of extracting gold from sea water. FBI agent Tom Brant, aided by reporter Janet Lowe and Detective Lt. Jack Ryan, attempt to rescue him and crack the Nazi spy ring.br br Cast: br br Milburn Stone as FBI Agent Tom Brantbr br Jan Wiley as Janet Lowe, a reporterbr br Dennis Moore as Detective Lt.