Set after the German invasion of Denmark (1940), the film focuses on the Holger Danske (resistance group) resistance group's Bent Faurschou Hviid (known as Flammen) and Jørgen Haagen Schmith (known as Citron). In a bar, Bent flirts with a woman, who identifies herself as Ketty Selmer and disturbs him by saying his real name. Bent follows the woman and confronts her, whereupon she tells him that she is a courier running messages between Stockholm and Copenhagen.