The life in Morocco of an officer of the Foreign Legion, Colonel de Joyeuse.

Baron Arnold, a businessman, takes his young wife to Africa where he instructs her to seduce Captain Olivier, an intelligence officer. But Olivier illuminates the baroness on the unsavory activities of her husband as a weapons dealer and entrepreneur of revolutions.

As Hélène is conveying her husband's body across the Sahara, her convoy is attacked by looters. The young widow survives only to be taken to a remote desert village called Tirzit amidst a band of lonely, ailing men. She meets her husband's partner who tries to kill her. Hélène does not report him to the police but is curious to learn the reasons for his action. Before dying of a terrible fever, the man confesses that he murdered her husband.

At the beginning of World War I in a village in the country of La Marne, two families are against the marriage of their children. The war changes the positions.