During an air raid in London in 1941, a female German secret agent receives instructions from her superior to deliver some secret documents to a German officer at a rendezvous in an isolated cabin on the Normandy coast. The officer, in turn, is to give the woman instructions regarding future German espionage in Britain. The British learn of the plot, and they plan to intercept the German agent and send a British agent in her place. Another British agent is to kill the German officer, seize his documents, and retrieve the British female agent in the cabin. Two days later, Helene, ostensibly a German agent, meets Peter, a man in a German SS uniform, at the cabin. It is possible that they are two German spies, or the two British spies sent to replace them, or, if the British mission has been only partially successful, one German and one British spy. As the two attempt to discover each other's true identity during the night, they fall in love. By morning, there is no definite evidence as to the real nationality of either spy. [In the original version, the British intercept the German female agent but fail in their attempt to replace the SS officer. At the conclusion of the encounter between the agents at the cabin, they discover that they are enemies, and the British agent is shot by the German officer.]