Oregon fur traders are attempting to keep pioneers migrating westward out of the territory by inciting the Indians to attack their wagon trains. The U.S. Army sends Tex Masters (Tex Ritter) to uncover who is supplying the Indians with Army rifles. He and his pal Rawhide (Nelson McDowell) ---called "Lucky" in the credits and pressbook---join up with the wagon train headed by Benson (Frank LaRue) and his daughter Ruth (Muriel Evans). When a staged "accident" almost kills Benson, Tex discovers it was the work of Matt Grimes (Tom London), the train scout, but can't prove it. He and Grimes have a row when Tex insists that the train take a different route from the one Grimes recommends, and Grimes quits the train and goes off the set the Indians on Benson's outfit. Tex saves the train, but Ruth and her father now believe that Tex is in league with the Indians, and they fire him. In town, Tex and Rawhide see Grimes conferring with Steve Coleman (Reed Howes), a fur trader. That night, Tex sneaks into Coleman's store and finds a huge supply of Army rifles, ready to be sent to the Indians. He also hears Coleman telling henchman Slade (Nolan Willis) to wipe out the wagon train. Tex is accidentally locked in the storeroom, but gets free and sends Rawhide for the Army. Tex gets to the wagon train just as the attack by the Indians and Coleman's renegades starts.