Dressed to Kill
"Brian DePalma, master of the macabre, invites you to a showing of he lastest fashion...in murder". Dressed to Kill was less horror and more of a crime thriller (released in 1980), but we include it here. The movie starred Michael Caine as Dr. Robert Elliott, Dennis Franz as Detective Marino, Nancy Allen as Liz Blake, and Angie Dickinson as Kate Miller. The movie received mostly positive reviews, and was a huge financial success.
In this movie, housewife Kate Miller (Dickinson) is in therapy with Dr. Elliot (Caine). After a trip to a museum, she ends up having a one night stand with a man, and on her way out of the building, she is murdered by a blond woman with dark sunglasses. A call girl named Liz Blake (Allen) comes up on the body and the killer, who is actually a transsexual, sets Liz as his next target.
With the help of Kate's son, Peter, Liz finds out the killer was a "girl" named Bobbi. During one encounter, Kate quickly realizes that Dr. Elliot is also Bobbi. Bobbi is shot by police and put into an asylum, and life for Kate and Peter seemingly goes on unhindered.