A C.I.A. Agent is used as a pawn in an insane woman's plan to steal a Polaris submarine.

Bette Davis is Madame Sin, a sinister-looking, totally evil, half-Chinese woman who indulges in endless machinations. Ensconced in a Scottish castle that is packed with an array of spy gadgetry, she runs afoul with counter spy, American C.I.A. Agent Anthony Lawrence (Robert Wagner), who is out to counter her plots for control of a Polaris submarine.—alfiehitchie