Rosemary is relaxing in the apartment listening to a jazz record and reading a book, when Mrs. Castevet drops by unannounced with her friend Laura-Louise. Rosemary invites them inside, looking privately annoyed. When Mrs. Castevet remarks that she's looking "worn," Rosemary admits it is the first day of her period. Laura-Louise says her periods used to be so painful, her husband would give her gin. Mrs. Castevet gives Rosemary a gift from her and Roman wrapped in light pink tissue paper: a silver necklace with a locket identical to the one Rosemary saw Terry Gionoffrio wearing around her neck. Mrs. Castevet says the locket contains "Tannis" root for good luck. Rosemary feebly tries to decline the gift out of politeness, recognizing it as Terry's, but is cajoled by Minnie and Laura-Louise into trying it on.
Rosemary tells Guy about the necklace later that night. Guy jokes about the smell, but says, "Well if you took it, you oughta wear it." Just then, Guy receives a phone call from a man named Mr. Weiss who tells him that Donald Baumgart—the actor who recently won the role Guy was after—has gone blind, and that Guy is now their first choice. Guy goes for a walk to process the news. Rosemary pays Roman a visit, explaining to him how Guy's career has suddenly taken off. When Roman notices Rosemary's unhappiness, she explains that the role is physically demanding and will take up most of his time, her voice tearfully breaking up.
Taking a walk together, Rosemary and Hutch discuss Terry Gionoffrio's suicide. Hutch mockingly calls The Bramford "happy house." Back at home, Rosemary finds a large bouquet of roses and a waiting Guy, who apologizes for neglecting her in favor of his work and proposes that they conceive a baby. He has marked out on the calendar when they should try to conceive.
Guy and Rosemary share a drink by the fire, and are about to settle into a romantic, candlelit dinner, when Minnie buzzes at the door. Rosemary hopes to herself that Guy will not invite Minnie in, and though he does, she declines. Guy returns with two chocolate mousses that Minnie prepared for them to try. Tasting it, Rosemary remarks that it has a "chalky undertaste," but Guy disagrees, seemingly upset by Rosemary's pickiness. She ladles the mousse into her dinner napkin and pretends to have eaten it. As Guy watches the Pope make an appearance at Yankee Stadium on TV, Rosemary cleans up, appearing faint and dizzy. Thinking she's merely drunk, Guy walks her to the bedroom, eventually having to pick her up and carry her to bed.
Lying down, Rosemary imagines she is on a mattress floating in the ocean. As she falls sleep she mentions trying to conceive, but Guy tells her there's plenty of time. Back in her dream, Rosemary is aboard a yacht with a number of guests captained by an unknown man named Skipper reminiscent of John F. Kennedy, who then transforms into Hutch. Guy rips off her pajama pants on the yacht in her dream, and begins to unbutton her pajamas as she actually lies in bed. Back in her dream, Rosemary frantically covers her naked breasts and is then shown to be wearing a bikini, along with the other women on board. Rosemary asks "Isn't Hutch coming with us?" when she sees him back on land, and the Skipper replies, "Catholics only."
As the dream progresses, Guy slides Rosemary's wedding band off her finger, and then we see her lying flat on a platform being raised toward the ceiling of a large cathedral that resembles the Sistine Chapel. From land, Hutch cries out "Typhoon!" On the yacht's prow, a naked Rosemary walks past a young African-American sailor—The Bramford's elevator attendant—who advises that she "go down below." Rosemary descends into the yacht's cabin and lies down on a floral-print mattress. Around her, dozens of elderly, naked men and women—including Guy, Minnie, Roman, Laura-Louise, and others—gather around, chanting and drawing a design on Rosemary's body with red paint. Guy says he's afraid she's still awake, but Minnie says that as long she ate the "mouse," she'll remain immobilized and insensate.
A lady in a long, flowing white gown descends a staircase and suggests to Rosemary that her legs be tied down in case of "convulsions." Rosemary agrees, thinking the "mouse" she ate could be rabid. The lady tells Rosemary the music can be stopped if it bothers her, but Rosemary responds, "Please don't change the program on my account." A naked Guy approaches her as she is bound, and we see a man's hands groping Rosemary from her bound wrists down her body to her legs. The human hands then transform into feral, beast-like hands. Green smoke unfurls across the screen, and Rosemary locks eyes with the yellow-eyed demon on top of her, crying out, "This is no dream! This is really happening!" A hand covers her face with a blanket before she can protest further. A man dressed as the Pope carrying a coat and a suitcase approaches her, saying he heard Rosemary had been bitten by a mouse. Rosemary confirms this, her body rocking rhythmically as if in the middle of intercourse, and asks him for forgiveness for not coming to see him. The Pope forgives her and extends his ring for her to kiss, which has a charm identical to the one on the necklace given to Rosemary and worn by Terry Gionoffrio.
Minnie and Laura-Louise barging in on Rosemary's moment of relaxation is a mildly irritating imposition that anticipates more menacing intrusions to come. What seem like casual, ordinary gestures slowly reveal a nefarious plot, such as Minnie giving Rosemary theTannis charm, an ostensibly harmless gift that Rosemary feels rude rejecting. Laura-Louise, played by Irish-American lesbian comedienne Patsy Kelly, provides a broad comic foil to the sinister goings-on, making wisecracks that leaven the foreboding tone of the scene.
Like The Bramford and the secretary, the charm symbolizes secrecy and concealment: what it encloses is not an obscure herbal root that brings "good luck" (as Minnie maintains), but rather a mold or fungus called "Devil's Pepper" used in Satanic rituals. Crucially, Minnie gives Rosemary the charm on the first day of her period, indicating that the Castevets' have already been fed information about Rosemary's body and menstrual cycle, likely by Guy. The foul odor of the Tannis charm contrasts with the film's abundance of floral imagery, a key symbol of Rosemary's femininity, purity, and motherhood. Guy apologetically gives Rosemary a large bouquet of roses, and yellow flowers adorn her bedroom wallpaper. The yellow wallpaper is likely also a reference to Charlotte Perkins Gilman's 1892 short story "The Yellow Wallpaper"—another story about a woman's harrowing descent into madness.
The sequence in which Rosemary is drugged and raped is a baroque, harrowing descent into horror. The sequence unfolds in a series of small escalations: first, Minnie interrupts dinner with chocolate mousse; second, Rosemary notices a "chalky under-taste" to it—yet another symbol of concealment. Guy pressures her into eating it, an early clue that he is a conspirator. The fact that Rosemary does not eat more than a bite gives the scene to follow an added layer of nightmarish tension, given that the coven expects Rosemary will be fully asleep. Whether or not Rosemary is awake, asleep, or dreaming is made wholly ambiguous, until reality brutally intervenes when she exclaims, "This is no dream! This is really happening!"
Rosemary's vision is at first a dreamy melange of Catholic imagery and celebrity-culture affluence—a cinematic rendering of the theme of religion-as-theater. She imagines Guy forcibly disrobing her on a yacht, a gesture that foreshadows Guy's decision to sacrifice Rosemary's body and baby to the coven in order to advance his acting career. Rosemary, whose name deliberately evokes the Virgin Mary, is stripped nude in front of the other passengers, her breasts fully exposed, modeling her descent from a happy, expectant mother to an exploited, humiliated body. Polanski seems to emphasize the oppressive role of religious institutions in bringing about this descent, especially the Catholic Church, such as when the Skipper tells Rosemary "Catholics only," and when Rosemary's body ironically "ascends" toward the ceiling of what looks like the Sistine Chapel. Guy pulls Rosemary's wedding band off her finger, symbolizing the undoing of the holy sacrament of marriage, and when Rosemary finally lays down on a floral-print mattress around which the naked coven gathers, her most intimate qualities of womanhood and motherhood have been put on full public display.
Polanski frames Rosemary's defilement with quasi-religious ecstasy. Her rape is both ritual and spectacle: her arms and legs are bound, and a geometric shape is painted on her abdomen, turning her body into a kind of relic or artifact. The stylish woman in a white gown who tries soothing Rosemary before the rape occurs is yet another example of the film's tendency to wrap ominous forces in lovely, even glamorous exteriors. Extreme close-ups show Guy's hands and eyes morphing into Satan's hands and eyes, highlighting that the rape is transpiring on at least two levels: first, Guy is raping an unconscious Rosemary so as not to miss "baby night" (which is how he explains the claw-marks to Rosemary the following morning); and second, the coven has summoned Satan himself to impregnate Rosemary with the antichrist, Adrian. Like Rosemary's first dream, her second dream ends with her offering a confession to a male authority figure in the Catholic Church. This time it is The Pope himself, wearing the Tannis charm on his finger—Polanski's visual metaphor for the corrupt and evil nature of religious institutions.