While looking for work in the Wyoming Territory in the late 1800s, young Steve Miller finds hard-bitten horse rancher Jeremy Rodock wounded after an attack by cattle rustlers Barjak and Hearn. Rodock accepts Steve’s offer to help him back to his ranch and offers him a job as a ranchhand. After Steve makes camp and “cores” the bullet out of Rodock’s wound, a horse carrying the body of Rodock’s ranchhand Whitey approaches and Rodock vows to catch the rustlers who killed Whitey. The next day, upon reaching the ranch house, Steve meets Rodock’s sweetheart, the generous and feisty Jocasta Constantine, daughter of a Greek scholar who fled war-torn Greece. Later, head wrangler McNulty warns Steve that Rodock has grown evil from “hanging sickness,” Rodock’s propensity to mete out punishment by hanging. When McNulty later tries to kiss Jocasta, she insists that she loves only Rodock, who took her in when she was a troubled, frontier, dance-hall prostitute in Cheyenne. That night after Rodock gives her a pair of sparkling earrings, Jocasta promises to stay by his side, but Rodock believes she will “stray” when someone better comes along. The next morning, after McNulty announces that the east range horses have been stolen, Rodock gathers his men to hunt down the thieves. When Jocasta protests that the hangings have corrupted him, Rodock suggests that she should leave if she cannot accept his methods. After following the thieves’ tracks for days, Rodock rides to L. A. Peterson’s ranch to ask his old horse trading partner if he has stolen the herd, but Peterson, who claims Rodock cheated him out of his share of the horse business, orders him off the land. Days later, after Jocasta rebuffs McNulty’s advances, Rodock spies the two leaving the barn within minutes of each other. Suspecting foul play, a jealous Rodock fires McNulty and, after a fistfight ensues, orders him off the land. Rodock then asks Jocasta if she knew McNulty in Cheyenne, but she reminds him that he likes her because "she wasn't born yesterday." Later, when the illiterate Steve asks her to write a letter to his mother, Jocasta tries to convince him to leave the ranch before the hangings begin to haunt him. When she then pines openly for a peaceful life in town, Steve reaches out to comfort her but realizes she is Rodock’s girl. Months later, Rodock discovers that Peterson, Hearn and Barjak are stealing his horses. Along with Steve and several other ranchhands, Rodock kills Peterson and captures and hangs Hearn, but Barjak escapes. Returning Peterson’s body to his home, Rodock offers Mrs. Peterson and Peterson’s son Lars money to maintain their ranch, but the insolent Lars promises to avenge his father’s death. Meanwhile, McNulty and Barjak devise a plan to steal Rodock’s herd and later enlist Lars in their scheme. At the ranch that night, Steve insists that because Rodock could not be sure who killed Whitey, he should not act as the judge and jury. In reply, Rodock reminds him that in unfenced, frontier territory one must make one’s own law. Jocasta protests Rodock’s vigilantism as well and leaves to comfort Steve, who professes his love for her and begs her to leave with him. After Jocasta returns to the house, a drunken Rodock jealously argues with her. Days later, Steve proposes to Jocasta, who confesses that she blames her own lack of fortitude for turning to prostitution after immigrating to America and again declares her love for Rodock. Suddenly, Rodock barges in and accuses Jocasta of having affairs with McNulty and Steve. That night, as Rodock and the ranchhands celebrate a large sale to the Fargo stagecoaches, Jocasta remains in her room preparing to leave the ranch. Days later, when Steve discovers that another herd has been stolen, he, Rodock and ranchhand Abe saddle up to track the thieves. Before Steve departs, Jocasta promises to leave the ranch with him upon his return. Successfully tracking the rustlers to a nearby valley, where they have hidden the stolen herd, Rodock, Abe and Steve hold the men at gunpoint. Rodock then learns that McNulty has filed the mares’ hoofs to bloody stumps to keep them and their foals from wandering, thus allowing McNulty to leave them unattended while he returns to town and establishes an alibi. Once the foals have grown, he plans to flee with a herd of unbranded horses. Incensed by McNulty’s cruelty, Rodock forces all three men to take off their boots and march through the rocky cactus terrain toward the Fort Whitney jail. After days of walking, the men’s torn and bloodied feet horrify Steve, who begs Rodock to stop his cruelty. When Barjak finally passes out from the pain and McNulty falls to the ground begging deliriously for mercy, Rodock orders Steve to put them back on their horses. After the proud Lars accuses Rodock of living in a life grounded in greed and cruelty, Rodock, awakened by Lars’ honesty, sets the other men free and takes Lars home, where Mrs. Peterson tells Rodock that she holds no grudge against him. When Rodock offers to give them some horses to start again, Lars bitterly refuses any help and tells him that Rodock has taught him to be compassionless. Filled with pity for the boy and for himself, Rodock returns to his ranch, where Steve tells him that he is leaving with Jocasta, who laments that Rodock knows nothing of human feelings. Crippled by her words, Rodock returns to the house and pounds out his sadness on the piano. After the couple leave, Rodock finds Jocasta’s earrings and rides out to return them to her. Meanwhile, Steve tells Jocasta about Rodock’s change of heart in dealing with the thieves and his promise to give up hunting and killing men. Just then, Rodock finds the couple and hands Jocasta the earrings as a gesture of goodwill. After Jocasta begins to cry, Steve realizes she still belongs to Rodock. Trading his favorite horse for the wagon, Rodock then proposes to Jocasta on the trail back home while Steve rides off, carrying only a memory of the couple that helped him become a man.