At the beginning of the film, when the killer has entered the house after Christine, she locks herself in Cotton's office. As she does and she says "Get the hell out of here!", there is a shot at Christine from an angle where you can see the roof above her. The roof has a skylight that isn't seen in any other shot. This is there because of the original way that Cotton was supposed to get killed. Originally, he attempts to climb out the window and gets stabbed doing so.