When the Pony Express is disbanded, rider Tennessee Colby decides to accompany his best friend and fellow rider, Tommy Logan, to his ranch in Adobe Wells. Their pal Fiddlefoot goes with them, and the end of their journey becomes lively when they reach Adobe Wells in the midst of a bank robbery. Tennessee so successfully helps foil the thieves that Marshal Bat Matson offers him a job as a deputy. While Tennessee settles into his new life as a lawman, Fiddlefoot becomes a ranch hand for Tommy's sister Mary, and Tommy resumes his friendship with Walt Bledsoe. Unknown to Tennessee, Bledsoe is the leader of the gang that attempted the bank robbery, and is in league with freight company owner Hobart Patterson. In order to maintain his highly lucrative shippping monopoly, Patterson uses Bledsoe and his thugs to terrorize the local ranchers and keep the territory in a state of constant lawlessness. Tommy, who will do anything for money, does not object to Bledsoe's tactics, and agrees to help him dispose of government official James P. Westfall, who is due to arrive in Adobe Wells. Patterson, fearful that Westfall will recommend that the territory become a state, thereby endangering his operations, has ordered Bledsoe to get rid of him. After Tommy shoots Westfall during a stage stop in Dead Man's Gulch, outside of Adobe Wells, Bledsoe orders one of his henchmen, John Traynor, to impersonate the official. Meanwhile, Mary confides in Tennessee that she hates Tommy's association with Bledsoe, and Tennesseee and Fiddlefoot become suspicious when they see how much ready cash Tommy is carrying. When a rancher named Beecher threatens to ship his own supplies, Patterson orders Bledsoe to get tough with him. The gang attacks Beecher and his men one day, but Tennessee and Bat launch a counter-attack, during which Tommy is wounded. Soon after, Tennessee sees Tommy's injury and warns him that their friendship cannot protect him again. Tommy nonetheless shoots and kills Beecher on Bledsoe's orders, but prevents the gang from killing Tennessee. Tommy inadvertantly leaves behind a clue at the scene of the crime that leads Tennessee to arrest him, and Patterson worries that he will talk. Bitter about Bledsoe's desertion, Tommy tells Tennessee about Traynor, whom Tennessee then confronts. After being bested by Tennessee in a fight, Traynor confesses, fully implicating Bledsoe and Patterson. Tommy then escapes from jail and Tennessee is forced to shoot him during the chase. Later, Tennessee must escort Patterson and Bledsoe to their trial, but he promises Mary that he will return soon.
