As Marshal Tex Williams travels by stagecoach to the town of Rawhide, he hears a fellow traveler, a stranger named Smokey Rogers, boasting that he is the partner of the great Tex Williams. Before Tex can reveal his identity, Deuce Spriggens jumps onto the stage, pursued by gambler Slim Farley, whom he beat in a poker game. Tex protects the unarmed Deuce, earning his loyalty. Meanwhile, in Rawhide, Farley instructs his henchman, Chuck Gorman, to steal his money back from Deuce and kill him. When the stage arrives, Chuck recognizes Tex as the lawman he had a run-in with years earlier, and challenges him to a gunfight, which Tex wins. Tex explains the fracas to Sheriff Craig and introduces himself to an embarrassed Smokey. Tex, who asks Smokey to be his partner, soon reunites with his old friend, Frank Eaton, and Frank's daughter Ruth, who has grown into a beautiful young woman. When the Eatons and the local judge, Meade, urge him to help rid the town of the corrupt Farley and his brother Dan, Tex explains that he has quit his marshal post in favor of cattle ranching. Tex and Smokey stay with the Eatons, and when Frank is shot dead, they find a broken revolver piece which they assume belongs to the killer. Their visit to the gunsmith reveals that Slim is the only man in town who uses that type of revolver. Tex brings Slim in to the sheriff, but the jury that is named to try him is loaded with men who work for the Farleys. On the day of the trial, the Farleys' men trap Tex, Smokey and Deuce in the jail, and when the ranchers race to rescue them, a gunfight breaks out. After a long fight, Tex shoots Farley, and his men surrender.
Outside the land office in Placita, California, Pony Express agent Jack Forbes and his partner, Mack, shoot down another agent who is carrying a letter from the Washington, D.C. land commission registering Spanish land grants. The murder is part of their plan to steal the American land grants awarded to local Spanish ranchers, which will allow them to take over all their land. Soon after, Postmaster General Edwards visits Army captain Tex Williams to enlist his help in capturing the killers. Tex and his fellow soldier, Corporal Smokey Rogers, disguise themselves as Pony Express agents. Tex also sends their friend, Private Deuce Spriggens, to Placita, where Deuce finds the Spanish ranchers wondering why the land grants they registered months earlier have not been returned to them. Meanwhile, Tex and Smokey travel to California, and when they attempt to stop a stagecoach to ask directions to the Moreno ranch, passengers Angelita Moreno and Rosa assume they are American "banditos" and shoot at them. Finally, they convince Angelita to lead them to her father's ranch, where they deliver a letter from John Carlton, the Pony Express boss, asking for the transfer of some horses. Don Carlos Moreno explains that many of his horses have been stolen recently by bandits, and soon afterward, they learn that neighbor Don Diego has been murdered by white men claiming to have bought his ranch. Tex and Smokey quickly deduce that someone in the land office must be tipping off the outlaws every time a land grant is sent via the Pony Express, allowing the outlaws to steal the grants easily. Tex convinces Don Carlos to register his land with the government and posts Smokey and Deuce as watchmen for the ranch. When Forbes and Mac kill the Express agent delivering the Moreno land grant, however, Smokey and Deuce witness the attack and rush to warn Tex and Don Carlos. Soon, a gunfight breaks out at the Moreno ranch, which finally ends when Tex shoots down Forbes. The next day, Tex, Smokey and Deuce enjoy the Morenos' California hospitality.
