Federal marshal Len Merrick, [Kirk Douglas], with two deputies, rescues cattle rustler Tim “Pop” Keith, [Walter Brennan], from a lynch mob led by rancher Ned Roden, [Morris Ankrum], whose eldest son has been fatally shot in the back. Roden believes Pop is the killer, but Merrick insists on taking Pop to Santa Loma for a trial. The mob grudgingly agrees to Merrick’s plan, yet Roden vows to administer his own justice. As the shot that started the feud lingers in the air, Merrick notices a pocket watch near the body of the dead son, a clue that hints at a deeper truth behind the events.
Pop suggests they spend the night at his nearby cabin, and Merrick agrees, though the night becomes unsettled when Ann Keith, [Virginia Mayo], Pop’s daughter, ambushes the group. Merrick disarms her from behind, and she eventually joins them on the trek to Santa Loma. To throw off Roden and his ranch hands, Merrick chooses a harsh desert route to check for pursuit. The plan backfires, and Roden’s gang overtakes them in a tense, smoke-filled fight. In the exchange, Merrick’s deputy and close ally, Billy Shear, [John Agar], is wounded, underscoring how fragile their safety really is. Merrick then forces Roden’s son, Dan, [James Anderson], into a stalemate, buying time as the caravan presses forward, though the price is steep: Pop’s son loses hope, and Billy Keith dies in the aftermath.
A fragile trust begins to form between Merrick and Ann. Merrick reveals that a past lapse—when duty was ignored—cost his father his life, a confession that deepens Ann’s sympathy while warning her of the risk of loyalty to Pop. Meanwhile, Dan tries to loosen Merrick’s grip on the situation by bribing Merrick’s other deputy, Lou Gray, [Ray Teal], to help him escape. The plan leads to a dangerous confrontation at a poisoned waterhole, and a disagreement erupts among the group about which route to take. Most want to head for a river to the south; Merrick insists on reaching Santa Loma. Gray draws his gun, but Merrick shoots it from his hand, leaving three prisoners to manage as the tension rises.
Exhausted and sleep-deprived, Merrick finally collapses in the saddle. Pop, reluctant to shoot, holds his ground until Gray comes for his rifle; Pop shoots Gray and hands the weapon back to Merrick, restoring a fragile balance of power as they push onward.
Back in Santa Loma, Pop Keith is brought to trial. Merrick fights to prove Pop’s innocence, but the weight of evidence and the testimony against him are overwhelming. The verdict is guilty, and as the hangman’s noose tightens, Merrick uncovers the watch’s inscription: it is addressed to Dan, revealing that Dan was the killer of his own brother. Confronted with this revelation, Dan draws his revolver and grabs Ann as a shield. When Mr. Roden approaches, Dan shoots, killing him, and then races into a barn where a new gunfight erupts with Merrick. From the barn’s loft, Dan leaps onto the back of a horse, attempting a desperate escape, but, just like his dead brother, Dan is shot in the back. The story closes on a note of hard-won justice, duty, and the heavy price paid by those who chase it.
