Manuel and Carga are after the hidden map of a gold mine which is somewhere in the hacienda willed to Manuel’s brother, Don Careta. Following the third midnight raid on his home, Don Careta is fearful for the safety of his daughter Wanda, and sends for Jack Martin to help him. Manuel and Carga write to a hired gunman to kill Jack, on his way to Santa Fe with his pal Lopez, but the man is killed in a gunfight with the sheriff. Finding Carga’s letter on the body, and knowing Carga has never met the man, Jack decides to take the killer’s place and reports to Carga as well as to Don Careta, thereby learning the whole situation. But Piute, Indian spy for Carga employed by Don Careta, overhears the discussion between Jack and Careta and informs Carga. Carga kidnaps Wanda and her father, and traps Jack in a mountain cabin. They leave all three tied up in the cabin, set a dynamite charge and depart to search the Careta house for the map. But they forgot about accounting for Rusty, the Wonder Horse.