Upstart fur trapper Breck Coleman (John Wayne) agrees to lead and protect a group of pioneers trying to make their way on the treacherous Oregon Trail. Amid a harrowing series of trials, including an Indian raid, a blizzard, scorching desert sands and nearly unnavigable woods, Breck attempts to begin a romance with frontier woman Ruth Cameron (Marguerite Churchill). Meanwhile, he searches for the men who killed his mentor -- and who may be members of another wagon train traveling westward.