They're Coming to Get You! (1972)

Jane lives in London with Richard, her boyfriend. When she was five, her mother was murdered, and she recently lost a baby in a car crash. She's plagued by nightmares of a knife-wielding, blue-eyed man. Richard, a pharmaceutical salesman, thinks the cure is vitamins; Jane's sister Barbara, who works for a psychiatrist, recommends analysis; a neighbor Jane's just met promises that if Jane participates in a Black Mass, all her fears will disappear. Jane tries the Mass, but it seems to bring her nightmares to life. Is there any way out for her short of death or a living Hell?