The Civil War is over, and Medal of Honor winner John Benedict returns to his Colorado ranch with his wife and four children, accompanied by his loyal ranch hand, Free. As they roll into town, they are greeted by a group of locals and a keen-eyed Lieutenant Able, who pushes to recruit John’s son Morgan to West Point. John is hesitant, but Free quietly nudges him to ask Morgan, and the boy agrees to consider the offer.
The next day, while John hunts the mountain lion Morgan shot, danger descends from the mountains as Comanche raiders kill his dog and steal his horse. He races back to the ranch and arrives just as the raid ends, finding his family murdered and Free mortally wounded. Before he dies, Free reveals that the Comanche raid was led by a white man, hinting that the truth behind the attack is more complicated than it seems.
Driven by vengeance, John joins a posse to hunt the Comancheros. He heads south into Texas, instructing Sheriff Whitcomb to liquidate his stock and wire him the proceeds. He travels to a prison camp in Mexico and decides to recruit his own crew from the inmates, under the pretense of offering them work for his mine. He selects six hardened criminals: Hoop, a former Comanchero; Job, an escaped slave; Chamaco, a young gunslinger; Cholo, a reformed bandit; Quiberon, a charming but reckless man; and Zweig, a German known for his raw strength. John frees the group and promises a reward if they join him, but they double-cross him—except for Job, who stays on board. The others abscond with John’s money and return that night after spending it all, agreeing to stay with him. Hoop reveals that the Comanchero leader is called Tarp.
The band tracks down Tarp and his tribe, attacking their base and driving them off, though Tarp escapes. John rides after him, freeing the men from their earlier pledge; yet they decide to press on with John. The search for Tarp spans years, during which John forms strong bonds with his motley crew. Along the way, he crosses paths with his old ally Sheriff Whitcomb, now a U.S. Marshal, who is shocked by how brutal his old friend has become and refuses a drink, telling him his family would be ashamed. After driving away to drink alone in a saloon, John’s crew catches up with their leader, and Chamaco probes John about his family. The young man has begun to see John as a father figure, but when he hints that John could be his father, John angrily dismisses him. Chamaco responds by gunning down John, seemingly killing him. The group dissolves, with Job warning Hoop not to loot John’s body. The barkeeper and his daughter realize that John is not dead.
Elizabeth Reilly reaches John, nursing him back to health as the bullet narrowly misses his heart and exits through his armpit. She falls in love and begs him to stay, but John continues his quest to locate Tarp. En route he stops to have his horse re-shod but is captured by the commandant of the prison camp that he liberated. Later, Hoop encounters Chamaco running his own bar, and Hoop reveals that John has been captured; Chamaco orchestrates a rescue and reassembles the gang. John tells Chamaco that any son of his would never miss a shot like that.
Hoop then reveals that Tarp has been captured by the army and is due to be moved to a fort for trial. John heads off to intercept him, and the crew joins. On the road they discover a squad of dead soldiers ambushed by the Comanche. They reach the besieged fort where the lieutenant lies badly wounded and the fort is surrounded by the Comanche who want Tarp back. John warns that killing Tarp could end the siege, but the lieutenant refuses. The band and the soldiers fight off the attack. John lays dynamite to force a path for the attackers, and Chamaco is mortally wounded saving John from the next assault. The gang triumphs, and Chamaco dies in John’s arms. When Hoop urges him to execute Tarp, John instead walks away, stating that he no longer harbors revenge. Cholo asks why he spared Tarp, but John simply rides off, firing a final salute to the remaining members of the gang, and resolves to return to his ranch.
