World War I is raging, but Swedish store clerk Madeleine Goddard (Vivien Leigh) has not aligned herself with either side. When she meets German soldier Karl Von Marwitz (Conrad Veidt), she falls in love. Karl, who presents as a footman of low rank, is in fact a high-ranking official in the German army. Madeleine has secrets of her own -- she is a spy, working for the Allies. As Madeleine and Karl are pulled deeper into the war, their love may be the thing that saves their lives.