After moving into a creepy old apartment in Manhattan with her husband Guy, Rosemary Woodhouse begins to experience odd, unpleasant things happening to her. Guy becomes enchanted with their nosy neighbors, Minnie and Roman Castevet, after the older couple's ward commits suicide. Then Rosemary gets pregnant after a bad dream in which a horrible creature makes love to her. A caring Minnie keeps giving her some weird concoction for the pregnancy and Rosemary doesn't feel at all well. The only solution is, as the tag-line says, to "pray for Rosemary's baby."