Jules Vincent, a happy-go-lucky, outgoing French Canadian trapper in the wild Northwest, befriends a beautiful Native American girl, and although he makes an enemy of bully Mike Brody, he agrees to travel with him. When Brody tries to kill them, Vincent kills him in self-defense. He is pursued by a by-the-book, idealistic Constable Pedley, who believes in the mounties' credo "we always get our man." The country is rugged and fraught with dangers like white water rapids, avalanches, wolf packs and desperadoes. After capturing Vincent, the inexperienced Mountie finds he is in no shape to get back to civilization without Vincent's help. Pedley is torn between fulfilling his duty and freeing the man who has saved his life.

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.