During World War I, two French aviators, Captain de Boeldieu and Lieutenant Maréchal, are shot down and captured by German forces. They are taken to a prisoners-of-war camp, where they meet various other inmates from different social backgrounds and nationalities. Despite the harsh conditions, the prisoners form a sense of camaraderie and mutual respect. They invest their energy into planning an escape, using their diverse skills and ingenuity to bolster their morale. Maréchal and Boeldieu, in particular, forge a bond over their shared resolve to regain freedom.

As the story progresses, the prisoners are transferred to a seemingly impregnable fortress commanded by the aristocratic Captain von Rauffenstein. The interactions between de Boeldieu and von Rauffenstein reveal the complex nature of class distinctions and honor among soldiers. De Boeldieu orchestrates a daring plan to distract the Germans, allowing Maréchal and another officer, Rosenthal, a chance to escape. The narrative then follows these characters as they navigate their way through danger and uncertainty, driven by the enduring hope of reaching safety and returning to their homeland.