Cattle baron Matt Devereaux raids a copper smelter that is polluting his water, then divides his property among his sons. Son Joe takes responsibility for the raid and gets three years in prison. Matt dies from a stroke partly caused by his rebellious sons and when Joe gets out he plans revenge.

In the 1880s, soon after being paroled from a Southwest prison, rancher Joe Devereaux, a half-breed, is taken to see the governor, an old friend of Joe's father Matt, who has arranged a meeting between Joe and his three white half-brothers, Ben, Denny and Mike. Determined to take over the ranch now that their father is dead, the brothers offer Joe $10,000 to move to Oregon and forget the place. Joe refuses the offer, throwing the money into a spittoon, and then goes to the deserted Devereaux ranch house. While staring at a portrait of Matt, Joe's thoughts go back to a time when his father was still alive: One day, Matt discovers that his sons Mike and Denny are part of a gang of rustlers who are stealing cattle from him. Matt strikes Mike when he tries to justify the rustling by complaining about his father's low wages. Ben also demands higher wages and sides with his two rebellious brothers, and only Joe remains loyal to his father. As punishment, Matt banishes Ben, Mike and Denny, giving them only a few stolen cattle to support themselves. Days later, Matt is upset to find that Joe has brought home Mike and Denny, and that his exiled sons are mingling with his dinner guests. The guests include the governor and his young daughter Barbara, with whom Joe is smitten. Soon after discovering that his cattle are dying, Matt learns that his herd has been poisoned by waste in the river coming from the Associated Western Copper Mine. Matt and his sons demand that the owner of the mine, McAndrews, stop polluting the river, and when the miner rejects their demand, Matt vows to get an injunction against him. Before leaving the mine, Matt punches McAndrews and destroys the mining company's refinery. Later, Barbara tells Joe that she is not concerned about his Indian roots, but her father, who is prejudiced against Indians, wants the couple separated. When Matt discovers the governor's prejudice, he determines to have him removed from office. A trial concerning Matt and the mining company gets underway with Van Cleve, McAndrews' lawyer, making the case that Matt never sought to use the proper legal channels to handle his dispute with the miners, and that his attack was premeditated. During the trial, Matt's lawyer makes a deal with Van Cleve, in which McAndrews agrees to drop his charges in exchange for a promise by Matt to repair the damage from the attack on the mine. Matt reluctantly accepts the deal but is troubled by the part of the bargain that requires Joe to take the blame for the attack and be jailed. The court defeat, along with the shame he suffers when Ben, Mike and Denny refuse to abide by the provisions of the deal, causes Matt to have a stroke. After making a partial recovery, Matt tries to get Joe out of prison by asking Ben to sacrifice his share of the ranch, but Ben refuses. Matt dies while following Ben on a horse. Joe is permitted to leave prison to attend his father's funeral, during which he formally severs his ties with his brothers and proclaims a blood feud. As Joe comes out of his reverie, his mother enters the house and persuades him to forget revenge and leave the country. Joe decides to take her advice, but when Ben intercepts him with the intent to kill him, the two half-brothers engage in a hand-to-hand battle that ends when Two Moons, the Indian ranch foreman, shoots Ben dead. Time passes, and Joe and Barbara, now married, visit Matt's grave. There, Joe sees the down-turned lance, the Indian symbol for a blood feud, and breaks it in half, thus ending the fight forever.