Electra McDonnell and her Uncle Mick are nabbed red-handed robbing a safe full of jewels. The man catching them, Major Ramsey, offers her a deal: either she helps him break into a safe and retrieve blueprints vital to the British war effort or she is turned over to the police. Reluctantly she agrees but when she pulls the job, the safe is dead and a German spy is dead on the floor. A double agent is at work and she and Ramsey have to find out who.