A young Robert Mitchum stars as Pecos Smith in this classic Western, adapted from a novel by Zane Grey. Chicago tycoon Col. Lamberth (Thurston Hall) is prescribed a vacation by his doctor, so he heads out to his hacienda with his feisty daughter Rill (Barbara Hale). En route to Texas, Rill is accosted by some roughnecks and she decides to pass herself off as a boy. Subsequently, father and daughter witness the murder of a stagecoach driver (Bill Williams), a crime for which Pecos is blamed, while the true perpetrator is Brad Sawtelle (Harry Woods). After Pecos helps out the travelers, Rill convinces her father to hire him and his Irish-Mexican sidekick, Chito. Pecos soon finds out Rills true gender and love ensues, but Sawtelle still has a bone to pick, and by the time they reach the hacienda a full-fledged war has broken out.