In 1825, in French-controlled Corisca, elderly Antonio Della Rebbia is summoned by Alberto Barracini to a meeting in a desolate valley known as the "maquis" and is shot in the back by Alberto's brother Vincente. Following the custom of the island, Antonio is buried in the same spot where he was slain and is doomed to remain in unhallowed ground until his murder is avenged by his eldest son. Although the powerful Barracini family, who had been involved in land disputes with Antonio, are not immediately arrested for the crime, Antonio's daughter Colomba fights to have them brought to trial in their village, Pietranera. The Barracinis, however, produce a forged letter and a witness, Arrigo, who testifies that the "bandit" Padrino had asked him to deliver a letter to Antonio, inviting him to the maquis. The ruling French prefect declares the Barracinis innocent and insinuates that Padrino, a political fugitive, is guilty. Colomba's fury at the Barracinis' acquittal is tempered somewhat by the knowledge that her older brother Orso is soon returning home after ten years of military service in France. Colomba rides to the maquis, where Padrino, a family friend, and his servant, Brando, live in secret, and reassures him that Orso will do his duty. On his Corisca-bound ship, Orso, meanwhile, romances Lydia Nevil, an English aristocrat vacationing with her father, Col. Sir Thomas Nevil. Although he speaks fondly of his homeland, Orso denounces the Coriscan practice of vendettas and describes himself a man of peace and reason. Upon landing in the Coriscan capital of Ajaccio, Orso is met by Colomba, who immediately senses that he has changed. Colomba disapproves of the Nevils, whom she regards as frivolous, but encourages Col. Nevil to give Orso a double-barrel rifle from his gun collection. Orso then invites the Nevils to stay with him at Pietranera, angering Colomba. In Pietranera, Orso is given a hero's welcome by Vincente and Alberto's father Guido, the mayor. Despite the Barracinis' seeming display of warmth, Colomba warns Orso to be on guard, especially as the prefect has recently left Pietranera for Ajaccio. Later, when a frustrated Colomba reminds him of his vendetta duty, Orso informs her that he read the trial transcripts and is convinced the Barracinis are innocent. Orso then proposes to Lydia, who, unaware of the vendetta, happily accepts. Now desperate, Colomba meets with Padrino in the maquis and begs him to bring the prefect back to Pietranera. Posing as an aristocrat, Padrino secures an audience with the prefect in Ajaccio. When the prefect dismisses his request to return to Pietranera, Padrino forces him at knifepoint to ride to the village. At the Della Rebbia villa, Colomba, meanwhile, denounces Orso as a traitor and finally tells him that their father is buried in the unholy maquis. Even after Colomba shows him their father's bloody shirt with a bullet hole in the back, Orso refuses to carry out the vendetta. Just then, however, Padrino arrives with the prefect and the Barracinis. To convince Orso and the prefect of the Barracinis' guilt, Padrino then forces Arrigo to re-testify about the letter, and Arrigo finally admits that the Barracinis coerced him into lying. Enraged by the Barracinis' duplicity, Orso finally challenges Vincente, the elder brother, to a duel in the maquis. Although Colomba is thrilled, Lydia tries to talk him out of the fight and tells him that she will leave him if he goes through with it. Soon after Orso, armed with Col. Nevil's rifle, goes to the valley as arranged, Colomba learns from a servant that the Barracini brothers are planning to ambush him. Colomba races to warn Orso and insists on helping him search the fog-enshrouded forest. Orso surprises the brothers, then while holding them at gunpoint, instructs Colomba to disarm them. When the hate-filled Colomba spits on Vincente and claws his face, Vincente shoots her. Orso then shoots Vincente and Alberto, killing both, but is himself shot. After Colomba dies in Orso's arms, swearing her love to her brother, Padrino advises the grieving Orso to use his tragedy to guide his people to a better way, and reassures him that Lydia will be waiting for him.