 Government agents Jim Lane (Lon Chaney Jr.) and Sierra Pete (Noah Beery Jr.) are sent to investigate the breakdown of the U.S. Mail delivery in the La Paz country, which is carried by the Overland Company operated by Tom Gilbert (Tom Chatterton) and his daughter Barbara (Helen Parrish.) Aided by their friend, Buckskin Bill Burke (Don Terry), they discover that Frank Chadwick (Noah Beery), using white renegades disguised as Indians, is behind the trouble as he wants the mail franchise owned by Gilbert s stageline.