A horse-dealing family becomes quite rich after one of their mares gives birth to a green colt. Soon, however, rivalries abound between neighbors, and one of the green colt's family inheritor's waits fifteen years to enact his vengeance.

In 19th-century France, a green mare is born on the farm of Jules Haudoin, a horse dealer. The phenomenon makes the family wealthy, and when the mare dies, its portrait becomes the Haudoins' most treasured possession. Jules dies and leaves his estate to his sons, Honoré and Ferdinand. During the Franco-Prussian War, young Honoré Haudoin is betrayed to the Prussians by a neighbor, Zèphe Maloret, who has long envied the good fortune of the Haudoins. To save her son, Madame Haudoin is forced to submit to the embraces of a Prussian officer on the very bed under which young Honoré and his friend, Toucheur, are hiding. Honoré keeps his mother's rape a secret from all, including his brother, and for 15 years he waits for a chance to avenge himself on Zèphe. Finally, he hits on the plan of seducing Zèphe's daughter. Meanwhile, Ferdinand innocently promotes Zèphe for the position of mayor, and Honoré reveals to his brother the reason for his hatred. The foolish Ferdinand writes Zèphe a letter recounting the tale, and the letter gets lost. Honoré is further enraged to learn that the Malorets may know of his mother's disgrace. Fuel is added to the fire when a romance develops between Honoré's young daughter, Juliette, and Zèphe's handsome son, Noël. After considerable confusion and misunderstanding, Honoré recovers the letter and exacts his revenge by forcing Noël under the bed and "raping" the willing Madame Maloret.