Plot hole: It seems unlikely any mental institution would let a patient out to visit home for any length of time as happens in the movie with the killer and his mother.
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Suggested correction: Unlikely, but still possible. Almost every workplace has a situation in which a person is bending the rules.
Factual error: When Julie's undressing in the shower scene she steps out of a slip. Impossible as she was wearing pants, women wear slips only with dresses.