A Lizard in a Woman's Skin (1971)

In London, Carol Hammond lives in a fancy building with her husband Frank and her stepdaughter Joan. Carol is the beloved daughter of wealthy, prominent lawyer and politician Edmond Brighton; Frank is his partner in his office and has a love affair with Deborah. Carol's next-door neighbor Julia Durer is a depraved woman who promotes parties with drugs and orgies. Carol has psychoanalysis sessions with Dr. Kerr and is intrigued with a nightmare where she stabs Julia to death three times while a couple watches. When Julia is found dead in her apartment, efficient Inspector Corvin and his partner Sgt. Brandon are assigned to investigate. All the evidences point out to Carol, but was it a dream or reality?