During mid-1876, Captain Robert Parrish, Dale Robertson, is portrayed as his own worst enemy, never quite a “team player.” A former one of the youngest colonels in the Union Army, he now commands a company under General George Armstrong Custer, Douglas Kennedy. His fiancée Kathy, Mary Murphy, daughter of Parrish's commanding general, breaks off their engagement because he has not yet risen in rank.
Parrish’s blunt, confrontational approach earns him little sympathy among civilians when he chastises them and even threatens to “break heads” if they trespass on Sioux lands. Tensions escalate as the exasperated general—once a prospective father-in-law to Parrish—reassigns Parrish and his company to the Bureau of Indian Affairs. There, Parrish is outraged by how Native Americans are treated and refuses to carry out the Indian agent’s orders to shoot escaping charges.
He is court-martialed and travels to the Western frontier, where he visits his former commanding general—now President of the United States—Grant, John Hamilton, who demotes him to captain. The exchange spurs Parrish to push for peace rather than war. He convinces the President to come west to meet Sitting Bull and avert a larger conflict.
Back in the West, Parrish reconnects with Kathy, who has announced her engagement to Charles Wentworth, William Hopper, a former major who is now a war correspondent. Parrish’s mission expands as he works with captured Indians, including Sam, a former slave now among the Sioux, Joel Fluellen. Parrish meets with Sitting Bull, J. Carrol Naish, who agrees to meet the President in secret to discuss a possible path to peace. As conflicts with the Sioux escalate, Custer orders Parrish to guard supplies while the regiment moves out, and Sitting Bull’s scouts are killed, pushing the Sioux toward war.
The Battle of the Little Bighorn follows, devastating Custer’s command, wiping out many of his men and also eliminating Wentworth, Parrish’s rival in love. In the days after, Parrish attempts to befriend Sitting Bull and Crazy Horse, the Sioux leader played by Iron Eyes Cody, and guides the Sioux toward safety in the North. Parrish is then court-martialed again, stripped of his rank, and condemned to death by firing squad for treason. Sam warns Kathy that peace will be impossible if the Army carries out the execution, motivating her to appeal to Sitting Bull.
As the execution looms, Sitting Bull arrives at the fort with Kathy to plead with Grant. Parrish had told Sitting Bull that the Great Chief would understand, hoping for mercy. Grant, John Hamilton, intervenes and commutes the sentence. With the danger passed, Parrish is freed, and he and Kathy share a kiss. Sitting Bull raises his hand in salute and rides off with his people, leaving a fragile path toward reconciliation on the frontier.
