Other mistake: When Clint Eastwood arrives at Jessica Walter's house and she has made him dinner, he gets very angry at her and storms out the door stating it's over and he never wants to see her again. He speeds off in his car. It only takes him 1 second to leave through the door, walk to the car, open the car door, start the car, and speed out of the scene making a very loud tire noise. Jessica Walters follows him to the door and we hear the car racing from the scene instantly.
Continuity mistake: Donna Mills' tape gag is tight when being menaced by Jessica Walter, but when Clint finds her on the bed the gag is much looser and she can mumble.
