In 1875, rugged Argentine gaucho Martin Penalosa welcomes his lifelong friend, Don Miguel Aleondo, back to the Aleondo estancia, his ranch. Due to the death of his father, Miguel is returning to the ranch after a long absence, and the other gauchos mistrust his "city ways." During the fiesta celebrating Miguel's arrival, Martin takes offense when a fellow gaucho disparages Miguel, and kills him in a knife fight. Miguel allows Martin to be arrested, despite Martin's declaration that it is the gaucho way to fight for one's honor. In prison, Martin meets fellow gaucho Falcon and stiffly greets Miguel when he visits. Miguel explains that he arranged for Martin to serve in the army rather than be imprisoned, and assures him he will always be welcome at the ranch. Martin and Falcon then go to the fort overseen by tough disciplinarian Maj. Salinas, who admires the gauchos' courage even though he is determined to turn them into good soldiers. Martin resents Salinas' strictness, and one day, after the soldiers fight off an advancing group of Indians, Martin deserts. While he is riding, Martin sees an Indian carrying off a screaming woman, and succeeds in killing the Indian and rescuing the woman, who is Teresa Chavez, Miguel's fiancée. Despite the initial animosity between the arrogant Martin and Teresa, an aristocratic city-dweller, Martin escorts her to the Aleondo ranch. During their journey, an attraction between Martin and Teresa grows, and she is distraught when he is captured by Salinas' men. Determined to extinguish Martin's rebelliousness, Salinas has him staked out on the ground and leaves him there for several days. Martin refuses to submit, and one night, Falcon helps to free him. Before leaving, however, Martin challenges Salinas to a knife fight, and when Salinas tries to shoot him, Martin slashes his arm. During the day, a patrol pursues Martin but the gaucho scout leading them does not reveal his location. Martin then travels through a desert, where he comes across a bandit known as Valverde. Badly hurt when his horse fell on him, Valverde speaks only a few words to Martin before dying. Martin then assumes Valverde's identity and, joined by renegade gauchos, Indians and army deserters, starts a band of rebels who attempt to prevent the encroachment of civilization upon the wild pampas. "Valverde's" notoriety grows, and Salinas, who has left the military to join the police, despite his useless arm, suspects that he is actually Martin. Salinas questions Teresa, who professes ignorance, but she later persuades her maid, who knows one of the outlaws, to lead her to their hideout. Salinas follows them and is captured by Martin's men, but Martin, who grudingly respects his enemy, sets him free. Martin is both pleased and disturbed to see Teresa, but when she confesses her desire to stay, he kisses her passionately. Two weeks later, Salinas convinces Miguel to request that the militia be called to capture Valverde and his men. Later, Martin and Teresa, who have been living as husband and wife, ask Father Fernandez to marry them, but the priest, outraged by Martin's lawlessness, initially refuses. Father Fernandez does relent, but they are interrupted when they see Salinas and the federal troops ride by on the way to the gauchos' hideout. By the time they reach the camp, Martin and Teresa are horrified to discover that all of their friends have been captured or killed. Martin and Teresa then begin the arduous journey to Chile, where they hope to live safely, but when Teresa reveals that she is pregnant, Martin realizes that she cannot finish the trek through the mountains. Determined to marry Teresa despite the risk of capture, Martin searches for Father Fernandez. The couple finds the priest but when Gomez, Salinas' former sergeant, recognizes them, he calls the police and Teresa is apprehended, although Martin escapes. Father Fernandez apprises Miguel of Teresa's condition, and Miguel informs Teresa that he has arranged for Martin to serve only a three-year jail sentence if he turns himself in voluntarily. Teresa is uncertain, as she fears that Martin's need for freedom will cause him to die in prison, but does reveal his hiding place. Unaware that Salinas is following him, Miguel goes to Martin's hideout, and there tells him that he cannot purchase his freedom at the cost of the lives of Teresa and the baby. Seeing Salinas and his men arrive, Martin rides off, followed by Miguel. The gunshots and confusion start a cattle stampede, and Miguel is killed while trying to help Martin escape. Later, Martin slips into Teresa's room and confesses that he was wrong to cling to the old gaucho ways and now hopes to rectify his mistakes. Martin arranges to meet Teresa at the cathedral the next day, and Father Fernandez also summons Salinas. The priest urges Salinas to prove his strength by being merciful, although Salinas protests that some things cannot be forgiven. When Martin arrives, however, and tells Salinas that he will go with him voluntarily, after he marries Teresa, Salinas allows him to enter the cathedral with his beloved.