The Iron Horse (1925)

Brandon, a surveyor, dreams of building a railway to the west. He sets off with his son, Davy, to survey a route. They discover a new pass which will shave 200 miles off the expected distance, but they are set upon by a party of Cheyenne. One of them, a white renegade with only two fingers on his right hand, kills Brandon and scalps him. Davy is all alone now.