In Colonial America, Jim Smith (John Wayne) leads a group, including the intense Janie MacDougall (Claire Trevor), that tries to figure out who is supplying the area Native American tribes with weapons. He suspects corrupt trader Ralph Callendar (Brian Donlevy), but does not have proof yet. Jim's accusations fall on deaf ears with unsympathetic British commander Capt. Swanson (George Sanders). Worse, Callendar, sensing that Jim is on to him, frames the hero for murder.