On the Texas range, a band of five bank robbers faces down lone marshal J. D. Cahill. After dispatching the robbers' guide, a half-white, half-Comanche named Lightfoot whom J. D. knows and trusts, the marshal demands the men surrender, heedless of the fact that he is outnumbered. When they draw their guns, he reacts quickly, killing two and taking the other three prisoner on the long trek back to his hometown of Valentine. J. D.’s job has left little time for rearing his sons, seventeen-year-old Danny and twelve-year-old Billy Joe. Simmering with resentment, Danny has turned to hardened criminals Abe Fraser, Brownie and Struther, who plan to rob the town bank. As part of their plot, the four have been imprisoned for drunk and disorderly conduct, and now send Billy Joe to set the town barn on fire. As Sheriff Ben Grady and his deputies rush to contain the fire, Billy Joe releases the prisoners, who storm the empty bank. A townsperson who hears a noise in the bank alerts Grady, who along with Deputy Jim Kane rides over to investigate. Although Fraser has told Danny that the robbery would be nonviolent, he eagerly shoots Grady dead as Struther throws a knife into Kane’s chest. They then leave the bags of money with Billy Joe to bury and sneak back into their cells, providing themselves with the alibi that they were incarcerated at the time of the robbery. Before Billy Joe, horrified, returns home, Fraser warns him that if he crosses them, Danny will die. The next day, J. D. returns and is appalled to find Danny in jail. Upon learning that Grady is dead and the bank robbers have left no tracks for miles around, J. D. determines to go after them. The foursome is released from jail, prompting J. D. to deputize Danny and instruct him to help hunt the robbers. Before leaving town, J. D. brings Billy Joe to Hettie Green’s boardinghouse, and upon noting his son’s discomfort on spotting Fraser in town, says nothing. He then picks up Lightfoot as his tracker, and when Danny calls Lightfoot’s white wife a “squaw,” J. D. knocks him into the mud. The three traverse the nearby hills, and upon discovering a band of men, J. D. takes off to scout them. After Lightfoot chides Danny for disrespecting his father, whom everyone admires for his courage and intelligence, J. D. returns and orders Danny to help him confront the men, ignoring Danny's apprehension. Easily disarming the men, J. D. finds cash in their bags and, despite their story that they stole it from a Mormon drover, brings them into town to stand trial for the bank robbery. Danny protests that he thinks the men are innocent, but when his father presses him for more information, Danny backs down, fearful for Billy Joe’s safety. In town, Fraser, Brownie and Struther grab Billy Joe and hold a knife to his throat, demanding to know where the money is buried. Terrified, the boy confesses that he hid the money, then declares that Cahills do not like to be threatened. When they attempt to torture him, he breaks free and eludes them. Meanwhile, on the range, Danny witnesses another example of his father’s bravery when a mob approaches, eager to avenge Grady’s death by lynching the men in custody. J. D. asks if they are willing to die to take the men, and when no one moves, pushes through the crowd with annoyance. When they reach Valentine, they hear that Billy Joe is very ill and rush to Hettie’s. Waiting in the hallway while the doctor examines Billy Joe, J. D. apologizes to Danny for missing so much of his life and asks his son to accompany him and learn more about what he has devoted his life to. Just then, the doctor diagnoses Billy Joe with pneumonia, but assures J. D. that he will recover in time. Danny listens as J. D. tells Billy Joe that he will be fine because he is a Cahill, and promises the three will get to know each other better when Billy Joe is well. After J. D. leaves, Danny keeps watch over his brother, and in the middle of the night, Fraser enters, punches Danny and demands to know where the money is. Danny, hoping to save the men falsely accused of the bank robbery, urges Billy Joe to tell him, but the boy explains he must go to the site himself to search for the exact location of the money. Knowing Billy Joe is too ill to survive the rainstorm outside, Fraser commands the boys to return the money to him as soon as they are able, then forces Danny to vow on his brother’s life to obey. Days later, the band of men are convicted of the bank robbery and sentenced to hang. As the gallows are tested, the men, including a teenage boy, mourn their fate. Meanwhile, Billy Joe has recovered and now leaves Hettie’s with Danny. J. D., who has deduced that the boys were involved in the robbery, has instructed Lightfoot to follow them, assuming they will dig up the money, and is disappointed to learn that they are spending the day fishing. J. D. does not realize that his sons are seriously considering all that they have done wrong and what they can do to fix the situation on their own. Finally, that night, the boys go to the graveyard and begin to dig, while J. D. and Lightfoot watch. As soon as they have recovered the money, J. D. scornfully rides in, planning to scare them. However, the boys fight back valiantly, not knowing who is attacking, and escape, leaving Lightfoot with a broken leg and J. D. trapped beneath his horse. After J. D. wrests himself free and his horse runs off, he sets Lightfoot’s leg and continues tracking the boys on foot, with Lightfoot on horseback. Hours later, they buy a mangy horse for J. D. to ride and follow hours behind the boys, who have reached Fraser’s hideout in the hills. Finding no one there, the two wait, aware that Fraser will kill them once he has the money. When J. D. and Lightfoot approach, Brownie, hidden in the brush, shoots at them. Lightfoot stabs Brownie to death with a torn-off tree branch, but the outlaw manages to shoot him twice. As Lightfoot dies, J. D. vows to care for his family. Once night falls hours later, Fraser, Brownie and Struther approach Danny and Billy Joe, whose guns are drawn. Offering them three-fifths of the total loot, Danny explains that they buried the other two-fifths that was their share. Danny then demands that they take the money and leave, refusing to shake Fraser’s hand when he offers it. Although the three ride off, the boys know they will be waiting to kill them. Terrified and alert, they ride back to town, but are stopped by J. D., who orders them to go on alone and dig up their share, seemingly unconcerned that the robbers will follow and kill the boys. As soon as Danny and Billy Joe uncover the money, Fraser attacks and J. D. leaps out of hiding and kills Brownie, then runs out of bullets. As Fraser and Struther hide in the trees, J. D. reloads, explaining to his sons that he tricked them in order to lure Fraser out in the open. Just then, Struther returns and hurls a knife into J. D.’s left shoulder, where he has been wounded numerous times, but J. D. manages to kill him. When Fraser then attacks, Danny shoots him, and J. D., suspecting the man is faking death, shoots the ground near Fraser until he gets up and lunges for Billy Joe, allowing J. D. to kill him. When Danny hands his father the loot, J. D. promises to testify that the boys returned the money, and ask that Danny be released into his custody. Promising to spend more time at home, the marshal leads his sons to stop the hanging.