A reporter gets more than she bargained for when she tries to prove that a murder has occurred in Brian De Palma's disturbing thriller. Danielle (Margot Kidder) meets Phillip (Lisle Wilson) on a "Peeping Tom"-themed game show and, dodging her ex-husband Emil (William Finley), takes him back to her apartment. But Danielle has a separated Siamese twin sister, Dominique, who is not pleased about the overnight guest. Journalist neighbor Grace (Jennifer Salt) sees Phillip slaughtered by one of them through her window; the body vanishes before she can convince a skeptical detective (Dolph Sweet) to take a look. Determined to prove that she's right (and get a career-advancing story), Grace investigates, assisted by a private eye (Charles Durning), and becomes more involved in the relationships among Danielle, Dominique, and Emil than she ever expected.