Guy arrives home to find that Rosemary has chained the front door shut. She explains to Guy that Roman Castevet is in fact Adrian Marcato's son, Steven, and shows him Hutch's book, which contains a photograph of Steven at age thirteen. Guy is skeptical that witches could possibly exist in New York City in 1966, but Rosemary argues that the book was published not so long ago (1933), and accounts for a global network of witches' covens. She describes how their rituals—called sabbaths or 'esbats'—feature chanting and infanticide, insists that the Castevets are no longer welcome in their apartment, and demands that they immediately move out. Though seemingly horrified by Rosemary's words, Guy minimizes her concerns and maintains that the Castevets are harmless elderly people. Seeing her buried in Hutch's book, Guy warns her she shouldn't be reading it, and over her protestations, he takes it from her and places it on a high shelf.
Rosemary unleashes her story on Dr. Sapirstein, who projects warmth and understanding about her worries, but dismisses Rosemary's fears that Minnie might have been putting something in her vitamin drinks. Dr. Sapirstein tells Rosemary that Roman is in fact terminally ill, and that he and Minnie were planning to leave the city to take one last trip together. Dr. Sapirstein tells Rosemary he will tell them to leave sooner, so that Rosemary can spend the remainder of her pregnancy in peace. On the sidewalk in front of The Bramford, Rosemary sees Minnie and Roman off to Dubrovnik.
Looking near the top of the bookshelf, Rosemary asks Guy where Hutch's book went, and Guy says he threw it away so she wouldn't scare herself further. In shock and disbelief, she chastises him for throwing away a late friend's gift. She visits a bookstore, dropping her Tannis charm in a sewer along the way, and purchases two more volumes on witchcraft. One passage describes a coven's ability to blind, deafen, paralyze, and kill their victims; another reveals that rituals often require one of the victim's personal belongings. At home, Rosemary calls Donald Baumgart and asks how he is doing. She prompts him by saying that Guy "has something of his," and Donald casually explains how he and Guy exchanged ties at some point. Realizing Guy is a conspirator, Rosemary grabs cash, her witchcraft volumes, and her "hospital" suitcase, and flees The Bramford.
Rosemary goes to Dr. Sapirstein's office and tells the receptionist it's an emergency. While waiting, she reads a TIME Magazine with the cover story "Is God Dead?" and then learns after chatting with the receptionist that Dr. Sapirstein uses aftershave with the same odor as her Tannis charm. Disturbed by this revelation, Rosemary flees back into the streets of New York. She tries calling Dr. Hill in a pay phone booth and leaves an urgent message with his receptionist, who calls back asking whether Rosemary is Dr. Hill's patient. Rosemary says she's only seen him once. After they hang up a second time, Rosemary whispers "All of them. All in it together. All of them witches," to herself in the pay phone booth. After listening to Rosemary tell of the "plot" against her and her baby over the phone, Dr. Hill agrees to meet with her the following evening, but coldly dismisses her pleas to meet right away, saying he's upstate at his place of residence.
Meeting with Dr. Hill the next day, Rosemary admits that even Guy is in on the plot. She says he wears pajamas at night now to hide a mark, and insists that the coven members are clever, well connected, and probably made a deal with Guy to bolster his career in exchange for his collaboration: "They gave him success, and he gave them our baby." Rosemary pieces together out loud the fact that Guy traded ties with Donald Baumgart to bewitch him, and that Roman tipped off Guy to rush home and steal Hutch's glove to do the same. Dr. Hill tells Rosemary plainly that he doesn't believe in witchcraft, but that there are plenty of "maniacs" in New York City. He offers to take Rosemary to Mt. Sinai hospital that night, and puts her to rest in a bedroom. Rosemary drifts off whispering to her baby that everything is going to be okay.
Rosemary wakes up to find that Dr. Hill, not having believed her story, has merely called Guy and Dr. Sapirstein to take her away. In a low, menacing voice, Dr. Sapirstein tells Rosemary to put her shoes on and go quietly or they'll take her to a mental hospital. On their way out, they tell Dr. Hill that Rosemary just needs "rest," to which an uncaring Dr. Hill replies, "That's all it takes." Rosemary, Guy, and Dr. Sapirstein sit in silence in the backseat of a cab on the way back to The Bramford. Walking inside the building with Guy and Dr. Sapirstein, the same young elevator attendant from the film's beginning ominously greets Rosemary. She suddenly drops several contents of her purse onto the floor, and as the men bend over to gather them, Rosemary slides into the manual elevator and slams the door.
Emerging on the seventh floor, Rosemary runs through the hallway but does not know where to turn. Seeing the "up" button illuminate on the elevator behind her, she runs into her apartment, managing to chain the front lock just before Guy and Dr. Sapirstein can barge in. In the bedroom, Rosemary calls her friend Elise but reaches a babysitter, who tells her Elise is at the movies. Rosemary leaves an urgent message, as two men in suits sneak across the opposite room in the background. Hearing a noise, Rosemary turns to see Guy slowly emerge from around the corner, trailed by at least a dozen other Bramford residents and Dr. Sapirstein, holding a sedative. Assuring her that they want to "help" her, the crowd holds Rosemary down on her bed and gags her with a handkerchief while Dr. Sapirstein administers the sedative with a syringe. Feeling her stomach, Dr. Sapirstein declares that she is in labor. Elise calls back, but Guy hangs up the phone. Rosemary apologizes to her baby—little "Andy or Jenny"—for allowing this to happen, and falls unconscious.
The slowly building atmosphere of suspense and foreboding accompanying Rosemary's pregnancy crescendoes into an acute crisis. When she unleashes her intuitive feelings of fear and panic to Guy and Dr. Sapirstein, both men develop stratagems designed to manage her outrage. Guy feigns shock at the allegations, but ultimately vouches for the Castevets, and accuses Rosemary of reading too much. Whether or not the curious heroine is imagining or really seeing the supernatural phenomena around her is a hallmark tension in Gothic narratives, and the men around Rosemary continually aim to gaslight her into believing the former. Knowing that the book will convince Rosemary of the latter, Guy takes it away from her before throwing it away entirely.
In the final days before Rosemary's pregnancy, she continues to deduce that even her innermost circle is conspiring against her. Rosemary pieces together the "plot" in much the same manner that the viewer does: point-of-view shots reveal vital passages from the tomes on witchcraft she obtains to replace Hutch's book. When Rosemary reads that spells require one of the victim's personal possessions, she calls Donald Baumgart (voiced by acting legend Tony Curtis) and realizes that Guy took his tie, and later Hutch's glove.
The shot of Rosemary reading the "Is God Dead?" TIME Magazine cover story is one of the key images of the film. First, it obviously foreshadows Roman's proclamation at the end of the film that, "God is dead! Hail Satan!" and the fact that Rosemary is about to bear the child of the antichrist. It also exemplifies Polanski's critique of religious institutions as glitzy, corrupt, and morally bankrupt shams—the equivalent of a glossy magazine cover, with little substance contained therein.
Three years before Polanski's film and two years before Levin's novel, The Second Vatican Council had convened, waging debates before the entire world about how best to bring the Catholic Church into the twentieth century. The event was likely still fresh in the minds of audiences. The Pope appears in Rosemary's nightmare wearing the satanic "Tannis" charm, implying that Catholicism and Satanism are connected. In interviews promoting Rosemary's Baby, Polanski freely admitted he is an atheist. Originally a Polish-Jewish refugee, Polanski's history of trauma and alienation during and after the Holocaust likely led him toward a fierce interrogation of ideas concerning faith and God, as it did for a number of philosophers and thinkers of the postwar era. The film recasts the philosophical question as to whether the idea of God can survive in modernity by asking the viewer to believe that witches can do so.
Polanski's film and Levin's novel also incorporate the themes of Jewish writer Franz Kafka. The "Kafkaesque" has become synonymous with a nightmarish, illogical world in which bureaucrats and professionals routinely oppress, punish, delay, and withhold answers from the average citizen. Rosemary's last, desperate attempts to reach Dr. Hill in the phone booth is a case study in the Kafkaesque. First, she must leave a message with his receptionist, who hangs up. Then the receptionist calls back, asks if she is a patient, and hangs up again. After Rosemary tells Dr. Hill about the danger she's in, he's still unmoved, not agreeing to meet her that day. Dr. Hill coldly turns her over to Guy and Dr. Sapirstein in the following scene, suggesting that the medical establishment is as morally corrupt as the Catholic Church.