A veteran cowboy (Harry Guardino) finds planning a payroll robbery at Shiloh difficult when he forms a friendship with Randy and a wild stallion brings back his pride at being a top bronc buster.
During a drunken spree in the small Wild West town of Bannock, one of a half-dozen workers from a nearby ranch accidentally shoots an innocent man. Bannock's marshal, a righteous man named Jered Maddox (Burt Lancaster), comes to the larger town of Sabbath bearing the dead body of one of the revelers and demands the surrender of the remaining five from sheriff Cotton Ryan (Robert Ryan) and ranch owner Vincent Bronson (Lee J. Cobb), starting a confrontation that threatens to engulf them all.
When rancher Frank Tanner (Jon Cypher) hoodwinks local lawman Bob Valdez (Burt Lancaster) into shooting an innocent man, Valdez is remorseful and tries to take up a collection for the widow. Tanner won't hear of it, however, and punishes Valdez by driving him into the desert with a cross strapped to his back. Valdez is freed by one of Tanner's henchmen (Richard Jordan) and, after convalescing, begins waging a one-man war against Tanner, picking off his men with his trusty Sharps rifle.