Unhinged

Unhinged is a 1982 American slasher film directed by Don Gronquist in his directorial debut, written by Gronquist and Reagan Ramsey, and starring Laurel Munson, Janet Penner, Sara Ansley, Virginia Settle, and Barbara Lusch. The film follows three young women who, after suffering a car accident, are taken in by a mysterious spinster and her infirm mother at their rural mansion. Over the course of the next several days, the women are stalked by an unseen killer.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.