When Juliette marries Jean, she comes to live on his ship, on board of which are, besides the two of them, only a cabin boy and the strange old second mate Pere Jules. Soon bored by life on the river, she slips off to see the nightlife when they come to Paris. Angered by this, Jean sets off, leaving Juliette behind. Overcome by grief and longing for his wife, Jean falls into a depression and Pere Jules goes and tries to find Juliette.

During 1st WW, two French officers are captured. Captain De Boeldieu is an aristocrat while Lieutenant Marechal was a mechanic in civilian life. They meet other prisoners from various backgrounds, as Rosenthal, son of wealthy Jewish bankers. They are separated from Rosenthal before managing to escape. A few months later, they meet again in a fortress commanded by the aristocrat Van Rauffenstein. De Boeldieu strikes up a friendship with him but Marechal and Rosenthal still want to escape...