Revealing mistake: Costner is supposed to be nude after he gets out of the water and is watching Kicking Bird wandering around in his camp; however, a close look in the lower left of the scene will show Costner is wearing skin-colored panty hose. The elastic waist band is quite visible, cropping didn't get it all out. (00:54:20)
Revealing mistake: In the extended version of the film during the buffalo hunt, there is a shot of a buffalo making a turn and in the distant horizon, you can briefly see a modern radio tower on top of a hill.
Revealing mistake: During the buffalo hunt, where the buffalo turns to charge the fallen Indian, the buffalo has a nose ring used for leading domestic animals.
Revealing mistake: In the scene where Dunbar comes to the Indian camp with the wounded woman he found, she is supposedly knocked out. However, when the Indian warrior grabs her wrist and pulls her to the tribe, she is also hanging strongly, with her hand around his wrist.
Revealing mistake: At the end of the movie, just before Dunbar arrives at the winter camp in the mountains, after being rescued by Wind in his Hair and his men, an old Indian man looks up and see them coming down the mountain. The old man is wearing thermal underwear under his leather tunic.
Answer: He was mentally disturbed and was depressed about being assigned to a "dead end" post with no chance at advancement. Dunbar, the hero, choosing to be assigned to the frontier, just pushed the poor soul over the edge.
Mark English
In a word, the disease syphilis. The urinary tract problems and the Insanity are possible side effects.
What are you basing this on? What in the movie indicates that he has syphilis?