In 1759, frontiersman Jim Smith (John Wayne) has little time to romance Janie (Clair Trevor), daughter of his friend MacDougall (Wilfrid Lawson), because the Indians of Pennsylvania's Allegheny Valley are on the warpath, using weapons they got from traders. Jim persuades the governor of the territory to institute a ban on trading, but scheming trader Callander (Brian Donlevy) figures a way around the ban. Captain Swanson (George Sanders), the arrogant new commander of the Allegheny region, disbelieves Jim's claims that Callander is still trading with the Indians. As they've done before, Jim and his friends disguise themselves as Indians to destroy wagons carrying Callander's illicit goods, but the trader has a few tricks of his own.