In an elegant apartment building in New York, a young couple, Rosemary and Guy Woodhouse, embark on a new chapter of their lives as they move into their new home. Rosemary, a sweet and dreamy aspiring actress, is excited about her life in the big city and the possibility of starting a family. However, the atmosphere changes when they begin to interact with their peculiar neighbors, the Castevets. These eccentric elderly folks seem overly interested in the young couple, particularly in Rosemary's health.
As the couple settles into married life, Rosemary discovers that she is pregnant. Initially, the news fills her with joy, but soon she begins to experience strange and disturbing situations that make her doubt her own mental health. Her visions and nightmares become increasingly unsettling, and paranoia takes hold as she starts to investigate the mysterious influence the Castevets have over her husband.
Guy, an up-and-coming actor, begins to exhibit strange behavior, as if he is more focused on his career than on his wife's well-being. Rosemary feels increasingly isolated and trapped, and her distress becomes a terrifying journey toward a dark revelation. As secrets and manipulations pile up, the reality of her pregnancy transforms into a nightmare that confronts her with the most chilling truth: she is at the center of something far more sinister than she ever imagined.