After rescuing a pony express rider from an Indian attack, Cal Sheridan becomes embroiled in the problems of the pony express company owned by Major Goodwin and his daughter Alice. The Goodwins are plagued by problems at their Ruby Valley stations, which are managed by Atkins, a bad tempered gambler and drinker. When the Major hires Cal to replace Atkins, Atkins joins forces with Claud and Mack Richards to rob the express. Using information supplied by Atkins, the Richardses steal the horses from the Ten Mile Station and kill station master Reese. Although the Richardses have made the robbery look like an Indian attack, Cal and Reese's daughter Norma become suspicious when they find the impression of a broken horse shoe in the killer's tracks. Later, in town, Norma discovers that the shoe belonging to Claud's horse matches the print found in the killer's tracks, and she accuses Claud of her father's murder. Claud rides off in pursuit of Norma, but she is rescued by Cal, who apprehends the outlaws, thus bringing prosperity to the pony express.