Dressed to Kill - Brian de Palma (1980)

Ha, ha, ha, ha, ha. thoughts/review to come soon.

Here's the synopsis from the wiki-page:

Kate Miller is a sexually frustrated housewife who is in therapy with New York City psychiatrist Dr. Robert Elliott. During an appointment, Kate attempts to seduce him, but Elliott rejects her advances. Kate goes to the Metropolitan Museum, where she for ten dialogue-free minutes has an unexpected flirtation with a mysterious stranger. Kate and the stranger "stalk" each other through the museum until they finally wind up outside, where Kate joins him in a taxi. They immediately begin to have sex in the cab, and their experience continues at his apartment. Hours later, Kate awakens and discreetly leaves while the man is asleep. But first, out of curiosity, she rifles through some of his desk papers and discovers that he has a sexually transmitted disease. Mortified, she leaves the apartment and gets in the elevator, but on the way down Kate realizes that she has left her wedding ring on the stranger's nightstand. She rides back up to retrieve it. The elevator doors open on the figure of a tall, blonde woman in dark sunglasses wielding a straight razor. Kate is slashed to death in the elevator.

A high-priced call girl, Liz Blake, happens upon the body and catches a glimpse of the killer, therefore becoming both the prime suspect and the killer's next target. Dr. Elliott receives a bizarre answering machine message from "Bobbi", a transsexual he is treating. Bobbi taunts the psychiatrist for breaking off their therapy sessions, apparently because Elliott refuses to sign the necessary papers for Bobbi to get a sex change operation. Elliott eventually visits Bobbi's new doctor and tries to convince him that Bobbi is a danger to herself and others. The police are less than willing to believe Liz's story, so she joins forces with Kate's revenge-minded son Peter to find the killer. Peter is an inventor. He uses a series of homemade listening devices and time-lapse cameras to track patients from Elliott's office. They catch Bobbi on camera, and soon Liz is being stalked by a tall blonde figure in sunglasses.

Several attempts are made on Liz's life. One is thwarted by Peter, who rescues Liz in the nick of time by spraying Bobbi in the New York City Subway with some homemade mace. Liz and Peter scheme to get inside Dr. Elliott's office to look at his appointment book and learn Bobbi's real name. Liz baits the therapist by stripping to lingerie and coming on to him. She distracts him long enough to make a brief exit and leaf through his appointment book. When she returns, it is Bobbi rather than Dr. Elliott who confronts her; they are the same person. Elliott/Bobbi is shot and wounded by a female police officer who looks like Bobbi and has been trailing Liz. She is the tall blonde figure who was tracking Liz all along. Elliott is arrested by the police and placed in an insane asylum. It is explained by a psychiatrist that Elliott wanted to be a woman, but his "male" side wouldn't allow him to go through with the operation. Whenever a woman sexually aroused Elliott, it was "Bobbi," who represented the female side of the doctor's personality, who became threatened. In a final sequence, Elliott escapes from the asylum and slashes Liz's throat in a bloody act of vengeance. She wakes up screaming, realizing that it was just a dream.