In early 1916, a French fighter plane is shot down during a reconnaissance mission over German territory. Aboard are Lieutenant Maréchal (Jean Gabin), a mechanic in civilian life, and Captain de Boeldieu (Pierre Fresnay), an aristocratic career officer. While waiting for them to be picked up by military police, Captain von Rauffenstein (Erich von Stroheim), the Junker who shot them down, invites them to lunch in the officer’s mess.
Transferred to the POW officers’ camp at Hallbach, Boeldieu and Maréchal are assigned to room with four fellow officers: Cartier (Julien Carette), a music hall performer; Rosenthal (Marcel Dalio), a wealthy Jewish couturier; a land surveyance engineer (Gaston Modot); and a provincial schoolteacher (Jean Dasté). Despite the wide difference in their backgrounds, the men get along well, united by a common desire to escape and return to the fray and sustained by the food parcels Rosenthal receives from his
parents.
Their nighttime activities are devoted to digging a tunnel; during the day they prepare the upcoming camp theatrical which Cartier will host — this despite
the news of a major German victory at Verdun which has sapped the POWs’ morale. During the show, Maréchal stops the performance to announce that the
French have retaken the Douaumont fortress at Verdun and the prisoners rise to sing La Marseillaise.
Maréchal is punished with solitary confinement. When he returns to the barracks weeks later, it is to find his colleagues preparing to escape through the now-finished tunnel. But before they can make their move, the officers are transferred to a new camp.
After a series of transfers and string of escape attempts, Maréchal and Boeldieu are sent to the “escape-proof” fortress at Wintersborn, where they are reunited with Rosenthal. The commandant is none other than Rauffenstein, who, wounded in action–his head now in a neck brace and white gloves hiding his scarred hands–has been assigned to a behind-the-lines desk job running the fortress.
Embittered and bored, Rauffenstein attempts to strike up a friendship with de Boeldieu by appealing to their class affinities. But it is Boeldieu who organizes an
elaborate diversion to cover an escape attempt by the working-class Maréchal and the Jew Rosenthal.
Playing the decoy, Boeldieu commits the ultimate sacrifice for his comrades when he is fatally shot down by the reluctant Rauffenstein.
Fighting exhaustion, cold and hunger, Maréchal and Rosenthal painfully make their way through the mountains toward the Swiss border. Slowed down by Rosenthal’s sprained ankle, the two men argue and make to separate, but the strength of their friendship keeps them together.
They find temporary refuge at the farm of a German peasant, Elsa (Dita Parlo), whose husband has died at the front. Maréchal and the lonely Elsa become lovers. But when Rosenthal’s ankle heals, it is time for the two men to pursue their road. Maréchal promises Elsa he will come back for her after the war. Finally reaching the frontier, just missing being captured by a German patrol, they cross the border into Switzerland, freedom, and a return to he war.
