The action takes place in occupied Czechoslovak Republic after assassination of Schutzstaffel (SS)-Obergruppenführer and General der Polizei Reinhard Heydrich, acting Reichsprotektor of the Protectorate of Bohemia and Moravia In Prague on 27 May 1942.Jirka is the boy whose family was murdered in the village of Lidice as repercussions for the assassination of Heydrich. He stays with his uncle - engineer Petr Lom. Marta - a young girl leaving next door, working at the post office helps to take care of the boy. Lom has just started working on the military airport, governed by Sudeten-Nazi named Ullman. Resistance is quite active in the airport, collecting arms and grenades and communicating with allies, sometimes doing some small diversion. They have a lot of great intel thanks to secretary Jana Tomesowa, who is trustee of Ullman and has access to a lot of restricted informations. Jirka also starts to help at the airport, but he's filled with sorrow and need of revenge. He's caught stealing grenade and arrested by gestapo. Later he's shot. When Jana sees it she faints, and Ullman finds some secret message she had with her. He tells he has found something to his gestapo friends and goes to the warehouse to investigate it himself. In there he's killed by resistance, by being pushed onto transformer. Gestapo starts arresting and searching houses of airport workers, and it turns out that Marta is working with Germans as informer. Lom doesn't know that yet, he's struck by Jirkas death. He picks the gun from his hideout and walks back to the airport. The neighbours tell him truth about Marta. Lom kills her and helps Jana escape.Germans gather airport workers and threaten to kill them all if noone says who killed Ullman. Then Lom appears saying he did it and killing men from gestapo who killed Jirka. He's killed by the soldiers. Workers go back to work.In last scene, dying Lom has vision of the future. He sees woman with gun (symbolizing Chechoslovakia) going forward with war attrocities around her. However she doesn't stop until the war is over and Czechoslovak flag appears on mast.