Sitting Bull is a 1954 American-Mexican Major Robert Parrish (Dale Robertson) of the 7th Cavalry is considered by some to be his own worst enemy because he's not a "team player". Formerly one of the youngest Colonels in the Union Army during the American Civil War, he is now a company commander under Lt. Colonel (formerly Brevet Major General during the Civil War) George Armstrong Custer (Douglas Kennedy). His fiancée Kathy (Mary Murphy), daughter of Parrish's commanding general, breaks off their engagement because he has not risen in rank.
Parrish gains no friends amongst the civilian community when he chastises them and threatens to "break heads" when they violate Sioux lands. Custer and Parrish's exasperated General and once prospective father-in-law reassigns Parrish and his company to the Bureau of Indian Affairs where Parrish is outraged at the treatment of the Indians and refuses to carry out the orders of the Indian Agent to shoot his escaping charges. Parrish is court martialed and visits his former commanding general—now President of the United States--Ulysses S. Grant—who demotes him to Captain. Parrish convinces the President to come to the Western frontier to meet Sitting Bull and prevent a war.
Back in the West, now Captain Parrish meets Kathy who has announced her engagement with Charles Wentworth (William Hopper), a former major and now a war correspondent. Using captured Indians, including Sam, a former slave now a Sioux, Parrish meets with Sitting Bull (J. Carrol Naish) who agrees to meet the President in a secret meeting. Further conflicts with the Sioux lead Custer to lead his Regiment out assigning Parrish to guard supplies.
Following the Battle of the Little Bighorn that eliminates Custer, most of his men, and his romantic rival Wentworth, Parrish tries to befriend Sitting Bull and Crazy Horse (Iron Eyes Cody). As Parrish knows the US Army's plan of attack, he leads the Sioux to safety in the North. Parrish is court-martialed again, stripped of his rank, and sentenced to death by firing squad for treason.
As the execution is about to take place, Sitting Bull comes to the fort to speak with President Grant. Parrish had told him "the Great Chief will understand," believing he would show mercy to him because his only intention was to prevent more killing. Sitting Bull's pleads with Grant to spare his life. Grant then commutes his sentence.
