In Dakota territory in the 1870s, White Bull, a young Sioux, proves his manhood by catching and training a wild colt he names Tonka. When a cruel cousin claims the horse as the privilege of rank, White Bull lets Tonka go. The horse ends up in the hands of a captain in the US cavalry about the time that Sitting Bull gathers the tribes to confront the growing US presence, epitomized by the bigoted General Custer. All paths, including those of White Bull and Tonka, lead to the confluence of the Little and Big Horn rivers.