Like many (or all) of the horror movies I've seen, I first saw a clip of Rosemary's Baby on Bravo's 100 Scariest Movie Moments. The scene they chose was the dream-cum-nightmare of Rosemary (Mia Farrow)'s rape, and in it Rosemary's cry of, "This is no dream!" still sends shivers down your spine.
This movie tells the tale of a young couple, Rosemary and Guy Woodhouse, who move into an old apartment building with a bad reputation. Rosemary meets a woman in the basement of the building who tells her that she is staying with the Castevets, and elderly couple whose apartment was once part of Rosemary's. A few days later, however, the woman is dead from jumping out of her window. By the body outside, the Woodhouses make the acquaintance of the Castevents, who prove to be nosy. However, Guy seems utterly fascinated with them, much to Rosemary's disapproval. Guy (who is an actor) manages to get a very important part because the previous actor has gone blind overnight. Guy gets very wrapped in his job, ignoring Rosemary. One day, out of the blue, he says he wants a baby. They plan a baby night, on which Minnie Castevent provides dessert chocolate mousse. Rosemary ends up passing out and has a strange dream in which a beast brutally rapes her. The next morning Rosemary wakes up with scratches on her back, of which Guy apoligizes for. Rosemary's anger at Guy for 'not missing Baby Night' is replaced by joy when she finds out she is pregnant. However, her pregnancy is very painful, and she begins to suspect her doctor may be letting this happen. She stops drinking the vitamin drinks given to her by a overly-helpful Minnie Castevent and her pain disappears one night at a party. Rosemary's suspicions are not gone, as she begins to discover the plot the surrounds her and her pregnancy.
This movie is not a slasher film, nor a ghost haunt. Why this movie deserves to be in the top 100 scary movies (or higher) is its suspenseful plot and an ending that will stay with you even after the movie is over.