The novel opens in 1942 with one of the main characters, Jenny Fields. Jenny comes from a wealthy family but she decided to study and be a nurse instead on focusing on finding a husband as her family wanted her to. One night, while Jenny was at the theater, she is groped by a soldier and Jenny fights back, injuring the soldier. After the incident, her family thinks that their daughter is behaving in a sexual promiscuous manner but the reality is that Jenny did not manifest any type of interest towards men.
Jenny soon builds herself a reputation in the hospital and she begins joking that she only wants to get pregnant and have a child instead of marrying a man and becoming a wife.
During a night shift, Jenny takes care of a badly injured Sergeant named Garp. The man was badly wounded and as a result he was only able to say the word Garp. The only thing that makes the sergeant happy is masturbating but his situation quickly deteriorates while Jenny takes care of him. In an effort to make him feel better, Jenny has sex with him but he dies only a few days later.
When it becomes clear that Jenny was pregnant, she is fired by the hospital and so Jenny returns to her parents’ home where she gives birth to a boy she names T.S. Garp.
After giving birth, Jenny becomes a nurse at the Steerling School where she continues her education in secret, reading everything she can get her hands on in her free time. When Garp is old enough, he gets enrolled in the school where his mother works now as a head nurse.
One night, Jenny cannot find her son until one of the students tells her that Garp has been thought by another student how to catch pigeons on the rooftop. Jenny goes to the rooftop just in time to catch Garp from falling from the four stories high building. In the same chapter, the narrator presents some faculty members and other children Garp is acquainted with, including the Percy children.
Jenny is extremely interested about her son’s future and when she is told that she doesn’t manifest any interest in sports, she makes it her purpose in finding a sport that will make Garp happy. Jenny talks with the wrestling coach at the school, a widowed man named Ernie who also has a daughter named Helen. Garp becomes interested in wrestling mainly because of Helen but he also expresses his desire to become a writer one day.
The action in the fourth chapter takes place years later, when Garp is ready to graduate. Garp began writing soon after expressing his desire to become a writer and he made a habit out of writing a short story every week. His affection for Helen is clear but he is too scared to admit it and thus he engages in various sexual activities with another girl named Cushie.
Garp continues to write to Helen but she tells him that she is unsure when they will be able to meet. Garp also tells Jenny that he wants to move to Europe to learn how to write and Jenny agrees to let him go but only if they go together. On graduation day, Garp and Cushie meet once more in secret and they have sex before they are discovered by Fat Stew.
That summer, Jenny and Garp move to Vienna where they both start writing. Unfortunately, none of them is notably talented and Garp has a hard time making himself write. One night, while Jenny and Garp were taking a walk, they came into contact with some prostitutes walking in the park. Jenny urges her son to approaches them and Garp become close friend and a regular client to one of the girls named Charlotte.
Garp finally begins working on his story which he entitles ‘’The pension Grillparzer’’. The story follows a man and his family as they travel from one hotel to another, offering reviews about the hotels they were staying at. At one of the hotels, the family meets a stranger who offers details about the way the wife’s father died a long time ago. The story then turns into a mystery, with the family being haunted and changes around in the hotel by various beings.
Garp stops progressing with his story and his life is turned upside down when Charlotte gets sick and dies despite receiving the best care possible. Garp sends Helen a letter through which he tells her that he wants to marry her but Helen is not sure whether Garp is serious or not. Garp began working on his story once more and Jenny finished her book which she entitles ‘’A Sexual Suspect’’.
Jenny and Garp return to the States, planning to have their stories published but when they begin talking with publishers they are rejected because their stories are not interesting enough. Garp and Helen marry soon after Garp returns home and soon enough a child appears. The couple names the boy Duncan and Garp takes over the responsibility of raising the child.
Jenny becomes famous after publishing her book but refuses to write another one. After Jenny’s mother dies, she changes drastically and is no longer the woman she once was. Garp also feels inadequate because instead of being known for his talent as a writer, he is known as the son a famous author.
One day, Jenny visits her son with one of her followers, a woman who cut her own tongue out as a symbol of solidarity with a girl who was raped and who had her tongue cut out by her aggressor. While Garp does not like the woman, he can’t forbid his mother from bringing her to him since she is the one who gives him money.
Garp manages to publish his novel but it does not have the same success as his mother’s novel had. What is more, Garp’s family life is affected by his affair with the family’s babysitter.
One night, while walking in the park, Garp stumbles upon a young girl who was molested. He tries to help the police men to find the one who molested the young girl and because of him the man who molested the young girl is caught. Because of this, Garp becomes famous and many hail him as a hero.
Garp and Helen have another son whom they name Walt. Soon after his birth, Garp has another affair with his babysitter and with the wife of one of Helen’s colleague’s named Alice. Helen found about the affair and about the previous affairs Garp had but chose to ignore them and start a relationship of her own with Alice’s husband, Harrison. The two affairs end when Helen breaks up with Harrison and then he and Alice are forced to move to another city after it was discovered that Harrison had affairs with some of his female students.
After Harrison and Alice move away, Garp finishes his second novel entitles Second Wind. Unfortunately, the novel is not successful at all and what is even worse is that anonymous writers start threatening Garp because of his book. Because of the response he got from the audience, Garp decides to stop writing.
Time passes and Garp and Helen have been married for eleven years. Garp still hasn’t managed to write a new book and he spends all his time taking care of his children and worrying about them excessively. Garp spends his time cooking for the family and thinking about various career plans. One day, Garp meets with Mrs. Ralph, the mother of one of Duncan’s friends. Mrs. Ralph tells Garp about her husband who abandoned her for a much younger woman and she even goes as far as to throw a book at him. The book she throws at him is entitles The Eternal Husband and this event makes Garp feel suspicious about Mrs. Ralph and about her son’s relationship with Duncan.
One night, while Duncan is at Mrs. Ralph’s house, Garp has a bad dream and he wakes up feeling the need to check on Duncan. Garp goes to get Duncan and while at Mrs. Ralph’s house he sees one of Mrs. Ralph’s lovers, naked in her room. Garp takes Duncan and the two return home.
In time, Helen became frustrated with Garp and with his behavior. Helen falls in love with one of her students, a young man who spent a year in Paris named Michael. Helen feels attracted to him but she initially tries to resist him. She finally gives in and has an affair with him but the situation comes to light when one of Michael’s former girlfriends gets jealous and sends Garp a note telling him about the affair. Garp gets angry and when Helen comes home she realizes that Garp found about the affair. Garp takes the children to see a movie while Helen meets once more with her lover, in her garage where she performs oral sex on him. When Garp returns home, he does not see the car parked in the garage and he hits it, injuring everyone in both cars.
Duncan lost an eye in the accident, Helen hurt her neck, Michael had his penis bit off by Helen and Garp broke his jaw and his tongue was torn up in the accident. Also, Walt, the youngest child, was killed in the accident. Because of his injuries, Garp became unable to talk for a while and he was traumatized to the point where he refused to speak even when he regained his ability to do so. Garp and Helen’s relationship was also affected by the accident but after a few months Helen went to Garp and told him that she wants another child.
After the accident, Garp wrote another book entitled The World According to Bensenhaver and the fifteenth chapter describes the action that happens in the first chapter of the book The World According to Bensenhaver. Garp insists to have his book published and he Jenny urges him to publish it as soon as possible. Helen is not as supportive as Jenny and she chooses instead to focus her time on her new child, a daughter named Jenny. Garp has his story published in an obscure newspaper.
Garp manages to find a publisher who is willing to print and promote his novel. Helen and Garp were not happy with how Wolf, the publisher, chose to promote the book, since he included details about the tragedy the family suffered just to inflate the sales and to make the readers feel more sympathetic towards Garp.
Garp and his family go to Vienna when Garp’s book is made public but they read about the reviews from there. While the book is either considered as being a complete masterpiece or failure, the sales are extremely good. His happiness is short lived however as Garp’s mother, Jenny, is killed during a political rally and Garp has to return to the States immediately to take care of his mother’s funeral.
Garp is told that he can’t attended his own mother’s funeral because the organization she was a member in insisted that they organize for her a feminist funeral. Because of this, Garp had to dress in drag to be able to attend his own mother’s funeral. Garp’s true identity is revealed when Pooh Percy, Cushie’s sister recognizes Garp and exposes him. The feminist crowd gets angry and Garp is forced to flee.
On the plane back home, Garp meets Ellen James, the girl who inspired many women to cut their own tongs out. Ellen tells Garp that she hates the feminist group and that she does not support their actions. Garp invites Ellen to come and stay with him and his family and Ellen is more than happy to accept.
Ellen is then introduced to the family but the moment is somehow tense as Fat Stew and Ernie had just passed away. While at Fat Stew’s funeral, Garp decides that he wants to buy the Steerling House and move into it.
Both Helen and Garp become teachers at the Steerling School while Garp also became involved in his late mother’s feminist organization even though he does not agree with their ideas. Ellen publishes her first writing piece but the response is not a positive one and Ellen is affected negatively by it. Garp tries to help Ellen by writing an essay defending her but his essay only enrage the feminists even more to the point where they try to assassinate him once.
Garp dies on the school grounds after Pooh Percy shots him. Life continues for the remaining characters and they all follow different roads in life. Helen for example, continues to be a teacher and died of old age. Ellen became a famous poet and she eventually dies in a car accident. Duncan loses one of his arms in a motorcycle accident and then later in life he dies in a non-glamorous way by chocking on an olive. The only character who remained alive at the end of the novel is Jenny who chose to become a nurse, just like her grandmother.
