Fred MacMurray and Joan Crawford are American honeymooners in pre-war Europe who are asked by British intelligence to help track down a missing agent.

On the eve of WWII, a newlywed couple (MacMurray and Crawford) about to embark on their honeymoon are suddenly given an important assignment by the British Secret Service. Despite a total lack of previous espionage experience, their mission is to obtain the top secret plans for a magnetic explosive mine. As they go about doing their duty, the pair confronts shady characters, secret codes, assassins, complex clues, deadly traps -- and Nazis. Based on the novel by Helen MacInnes.