The Bell Jar is the story of 19-year-old Esther Greenwood, the breakdown she experiences, and the beginnings of her recovery.
The year is 1953 and Esther Greenwood, having finished college for the academic year, has won a one-month paid internship at Ladies Day magazine in New York City. She and eleven other college students, also contest winners, are set up in the Amazon Hotel and juggle work with the scheduled events the magazine has created for them. Esther's manager at Ladies Day, Jay Cee, is a hardworking, hard-hitting, homely professional who expects much of Esther. Esther's primary friend during this month is Doreen, a glamorous platinum-blond student who chain-smokes, dresses provocatively, and does not take her work seriously.
The reader learns early on about the struggles in Esther's life. Her father died when she was nine; while Esther wants to be a poet, her mother wants her to learn shorthand so that she will have a vocation to fall back on. She has been dating Buddy Willard, a Yale medical student who bores her and minimizes those things she holds dear: poetry, literature, creation. Buddy has asked her to marry him, but she told him she never plans to marry. During this summer, Buddy is in a sanitarium recovering from tuberculosis.
One evening at the beginning of the novel, Esther and Doreen head out in a cab, only half-intending to go to the event scheduled for the contest winners. They end up in a traffic jam, and are approached by Lenny Shepherd, a local DJ, and his friend Frankie. Lenny latches onto Doreen and Frankie makes his excuses and leaves. Esther, Doreen, and Lenny end up back at Lenny's lush apartment, with Esther watching as Lenny and Doreen get drunker and more intimate. She eventually walks back to the hotel, leaving Doreen with Lenny. In the middle of the night, Doreen is brought to Esther's hotel room door, vomiting and drunk, and Esther leaves her in the hallway, deciding she will distance herself from Doreen.
Esther decides on another day that she will ignore several Ladies Day–scheduled functions in order to lounge in bed and later spend time in Central Park. Jay Cee, however, calls and asks Esther to come to the office, where she talks very frankly with her about preparations she'll need to make if she wants to become a New York editor. Esther spends the rest of the morning reading manuscripts at the office, and then catches up with the other contest winners for a banquet. At the banquet, she gorges on caviar, followed by crabmeat salad. At a movie premier later in the afternoon, she begins feeling ill and catches a cab home with Betsy, another contest winner who is as wholesome as Doreen is audacious. Back at the Amazon, she is deathly ill and learns later that all of the contest winners at the banquet ended up with grave food poisoning from the crabmeat salad.
As she is recovering from the food poisoning, she gets a call from Constantin, a UN simultaneous interpreter who is acquainted with Mrs. Willard, Buddy Willard's mother. Esther goes out with Constantin to an ethnic restaurant and meets other fascinating people, who by their accomplishments make her feel her own inadequacy. She plans to seduce Constantin, reveling in the thought of losing her virginity to an acquaintance of Buddy Willard's mother, but they end up merely sleeping next to each other in his apartment.
As the internship ends, Esther is feeling more and more disjointed and unable to enjoy her experiences in New York. During a photo shoot for the magazine, she is unable to hold her artificial smile, and begins weeping openly. Her final night in the city, she goes on a date with Marco, a woman-hater who begins the evening by giving her a diamond stickpin, and later assaults her. He demands she return his diamond, which was in her handbag; the handbag flew out of her hands and landed somewhere in the mud during the assault. She leaves Marco on his hands and knees in the mud, looking for his diamond. She returns to her hotel room and, one by one, drops her clothes and undergarments out of the window of her room.
The next day Esther trades Betsy her bathrobe for a skirt and blouse, and makes the trip home to New England. Her mother picks her up and immediately tells Esther that she did not get accepted into a writing program she'd applied to; Esther feels hopeless as she looks at spending the rest of the summer in her mother's house.
Over the next several weeks, Esther is able to do little and slides into depression. She continues to wear the blouse and skirt she bartered for with Betsy and refuses to bathe or wash her hair. She tries to write, but finds she is unable to read, write, or sleep. When she asks the family doctor for more sleeping pills, after having received a prescription the previous week, the doctor refers her to Dr. Gordon, a psychiatrist.
Esther dislikes Dr. Gordon, a young, successful man with what appears to be a perfect family. When she isn't cooperative with Dr. Gordon, he suggests to her mother that Esther would benefit from elctro-shock therapy. Esther undergoes one treatment, a harrowing, painful experience that leaves her terrified of the procedure. At this point, Esther's reasoning becomes more scattered and she becomes obsessed with suicide. After several unsuccessful or aborted attempts — slitting wrists, hanging, drowning — she wedges herself into the crawlspace of her house and takes dozens of sleeping pills. She is missing for several days and wakes up in a hospital. Later, she is moved to a state mental hospital.
With the financial help of novelist Philomena Guinea, who funds Esther's college scholarship and who was once herself committed to an asylum, Esther is moved to a private hospital that is much more comfortable and humane than the state hospital. Esther meets many of the patients, including Joan, another student from Esther's college and a one-time romantic interest of Buddy Willard. Esther also meets Dr. Nolan, a female psychiatrist who understands Esther far better than Dr. Gordon did. Dr. Nolan isn't scandalized when Esther admits that she hates her mother, and the doctor also limits all visitors to Esther — a gesture Esther is grateful for. Dr. Nolan is aware of Esther's terror of electro-shock treatments, and later when these treatments are administered to Esther, they are a much less harrowing experience, both physically and emotionally, because of Dr. Nolan's care.
Esther continues to have contact with Joan, who she interrupts in a lesbian embrace with another patient. Joan eventually moves into an apartment, becoming roommates with a nurse from the hospital. Esther agrees to come visit Joan in the new apartment, although has no intention of following through. With Dr. Nolan's help, Esther purchases a diaphragm, which frees her from the fear of pregnancy should she decide to lose her virginity. That day, she meets a man named Irwin, a bookish 26-year-old math professor; they end up at Irwin's home, where they make love. Following intercourse, Esther finds she is hemorrhaging heavily. She asks Irwin to drop her off at Joan's apartment, and Joan takes her to the emergency room where she is treated.
Joan soon moves out of her apartment and returns to the hospital. One morning, Joan's psychiatrist comes to see Esther to tell her that Joan has not returned from the previous evening; Esther is asked if she has any idea where Joan might be. Esther doesn't. Later, Joan's body is found in the woods; she has hanged herself. Buddy Willard comes to the hospital to visit Esther, and asks whether there is something about him that drives women crazy, as both Esther and Joan ended up in a mental hospital after being with him.
The novel ends somewhat openly, with Esther stepping into a room in the hospital where she will be interviewed to determine whether she can leave the hospital and return to college.