Some people need to see this movie again (spoilers)
1. There is nothing supernatural in this film. Barry's character is insane and it is told from her point of view.
2. There are no plot holes in this movie. The story is told from the point of view of an insane person, but you only slowly become aware of that fact. The "plot holes" you see are just you not getting the movie.
I think the most interesting aspect of this film is what drove Barry's character insane. She is a good person who gradually realized that she was married to an insane serial killer. She couldn't handle it and it drove her crazy.