In search of greener pastures, Senator William J. Tadlock (Kirk Douglas) heads west, with scores of settlers following behind. Tadlock has hired an experienced scout, Dick Summers (Robert Mitchum), to accompany the caravan on the way from Missouri to Oregon. But hazards along the trail, and Tadlock's increasing megalomania, threaten to break up the expedition. Their problems get bigger when one of the pilgrims accidentally kills the son of a Sioux chief.