The Dark Mirror (1946) | FILM NOIR/THRILLER | FULL MOVIE

A woman suspected of murdering her doctor boyfriend has an identical twin sister. When both twins have an alibi for the night of the murder, a psychiatrist is called in to assist a detective in solving the case. Through a series of tests, he discovers which twin actually committed the crime, and in the course of his investigation he falls in love with one of them.

IMDb: https://www.imdb.com/title/tt0038455