Out of a job and at loose ends in the Mexican town of San Rafael, Owen Burke overhears a conversation between two Mexican vaqueros seated at a nearby table in the local cantina. After introducing himself, he learns they work for Don Enrique Hernandez de Allende at a horse ranch some distance south. The Don is planning a horse drive to California where his brother-in-law has a ranch. Owen knows those trails and hopes the Don might be in need of a guide. Arriving at the Don's ranch, he impresses the Don and his daughter, Rosa Maria. However, the ramrod, Chavez, who is suspicious of gringos in general and also guards Rosa Maria jealously, is not impressed. Despite Chavez's mistrust, Owen is hired as a guide for the drive. While scouting ahead on the drive, Owen is ambushed and left for dead. His attacker then leads a band of rustlers who drive off the horses. Because the leader resembles Owen and is riding his horse, Chavez believes the leader is Owen and vows to get even with him for leading them into a trap. With Chavez and his vaqueros pursuing him, Owen sets out to find the thieves, recover the horses, and clear his name. But first, he needs a horse.