This is one of my favorite Brian De Palma movies and certainly worth seeing. The first murder here is brutal and sets the stage for a great film. Margot Kidder looks hot here and we see a little skin as she plays a mentally scarred twin sister who has been separated from her conjoined sibling a while back, producing some very bad side effects if she forgets to take her medication. Just ask that poor black dude she stabs to death early on. A neighbor who happens to be a local reporter witnesses the murder. She tries desperately to get anyone to believe in what she's seen but gets road blocked at all turns. I love the split screen view after she has called the police to go investigate. The cops and reporter are shown going up to the apartment as the sick twin and her Dr. scramble to hide the body and clean up the mess just in time. The body is stuffed in the sleeper sofa, where it stays. The cops find nothing and the reporter drops the cake that may have proved her story. She's relentless though and keeps trying to prove what's she seen with the help of a P.I. she hires. She soon learns the secrets of her murderous neighbor, but it costs her something in the end. This movie is taut from start to finish and the end gives you a cold hollow feeling inside. It's not bloody, except for that first murder, or action-packed, but it really keeps your attention. I see a lot of people saying this movie is some kind of homage to Hitchcock. Feels more like an Argento film to me at times, especially that stabbing that starts the fun. You be the judge, either way, there's a lot to like here.