Epic western about a Union soldier in the American Civil War, Lieutenant John Dunbar, who after an act of suicidal bravery becomes a hero and is allowed to choose his next assignment. He requests the frontier and is assigned to a fort built somewhere in the Midwest. Dunbar arrives there to find the place deserted, he soon learns that a band of Sioux are encamped nearby. Having made contact, he quickly becomes absorbed into their way of life and begins to adopt their culture.