Dressed to Kill (1980)

Plot hole: After his mother's death, Peter sets a camera up outside her therapist's office, so he can see who goes in and who comes out; he thinks his mother's killer might be one of the doctor's patients - a tall woman with long blonde hair. All he sees is people going in and people coming out, and then he sees her - the tall blonde. Problem: He never saw her going in, only going out, which is critical, because the killer is the therapist - a tall man - wearing a long blonde wig and make-up. Of course no-one says anything about "We never saw her going in, only out, so it must be the therapist!"

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Kate Miller: Maybe there's something wrong with me.
Doctor Robert Elliott: There's nothing wrong with you.
Kate Miller: Do you find me attractive?
Doctor Robert Elliott: Of course.
Kate Miller: Would you want to sleep with me?
Doctor Robert Elliott: Yes.
Kate Miller: Then why don't you?
Doctor Robert Elliott: Because I love my wife, and sleeping with you isn't worth jeopardizing my marriage. Is it worth it to you?
Kate Miller: I don't know.

Trivia: This film's ending mirrors that of "Carrie," another film that this movie's director, Brian De Palma, made; at the end of "Carrie," Susan Snell has a dream of visiting the wreckage of Carrie White's house. Then Carrie's hand pops out of the ground and grabs Sue's arm. Susan wakes up screaming and is comforted by her mother. This film ends with Liz having a nightmare about Robert escaping from the institution, coming to her home and killing her. Liz wakes up screaming and is comforted by Peter.