T.S. Garp, the unexpected child of feminist icon Jenny Fields, enters the world under peculiar circumstances. Set during World War II, Jenny, an empathetic nurse, forms a unique bond with a severely brain-injured soldier, Technical Sergeant Garp, who can only utter his name as he succumbs to death. While holding the lifeless body of the soldier, she becomes impregnated due to his morbid priapism, leaving her child with an extraordinary legacy. Naming her son after the fallen gunner, Jenny embarks on a journey that would irrevocably alter both their fates.
As Garp matures, he discovers a passion for wrestling and writing, activities that evoke a lack of enthusiasm from his mother. Instead, her fascination lies in the complexities of human sexuality, a pursuit that ultimately leads to her influential work. Her book, Sexual Suspect, garners widespread acclaim, establishing Jenny as a feminist symbol and allowing her to create a sanctuary for troubled women in her home.
Meanwhile, Garp's literary ambitions bear fruit in the form of a debut novel that captures the attention of Helen Holm, the daughter of the wrestling coach. Their relationship flourishes into marriage, and they welcome two sons, Duncan and Walt. While Garp embraces fatherhood and his writing career, Helen dedicates herself to academia as a college professor.
Frequent visits to his mother's sanctuary offer Garp insights into the lives of its residents, including Roberta Muldoon, a transsexual former football player who finds refuge within Jenny's haven. During one visit, Garp learns of Ellen James, an 11-year-old girl who underwent horrific abuse leading to her tongue being cut out. Disturbed by the plight of Ellen, he discovers a group of women, the "Ellen Jamesians," who have taken a drastic stand by mutilating their own tongues in support of her suffering. To Garp's horror, Ellen herself has begged them to stop their actions, but their resolve remains unfaltering.
As Garp navigates the intricate strands of his existence, he becomes increasingly attracted to an 18-year-old babysitter caring for his children. The lines between youth and adulthood begin to blur as their relationship develops – a path that will yield profound implications for his life and relationships. Upon returning home, Garp faces a devastating revelation—the infidelity of his wife, Helen, leads to tragic consequences when he recklessly crashes into her lover's car, resulting in the tragic deaths of Walt and significant injuries to Duncan. This traumatic episode drives Garp to seek comfort with his mother, guiding him toward potential forgiveness and reconciliation with Helen.
Their reunion births a new chapter with the arrival of a daughter named after Jenny, a poignant reminder of their tumultuous history. However, their happiness is soon overshadowed by controversy surrounding Jenny's work at the center and her latest literary endeavors. In a bold move, she endorses a politician aligned with her ideals, provoking threats from those opposed to her stance.
In response, Garp pens a novel chronicling Ellen James's story and its aftermath, achieving commercial success as a biting critique of the Jamesians. Yet this newfound fame brings peril, as Garp begins receiving death threats from the groups he discusses in his book.
The narrative escalates when Jenny is murdered by an anti-feminist extremist during a political event. Following this tragedy, her center hosts an exclusive memorial service for women only – a choice that ignites outrage. Undeterred, Garp disguises himself to attend, only to be recognized by Pooh, an old friend from his past.
As Garp traverses this dangerous terrain, he finds himself in peril yet again. Fortunately, Ellen James intervenes, whisking him away to safety and expressing her gratitude for his novel about her life. The Jamesians, further inflamed by Garp’s presence at the memorial, serve as a prelude to impending violence.
Years later, Garp returns to his college as the wrestling coach, secretly longing to take up hang gliding. During a practice session, Pooh reemerges and curtails Garp's dreams in a burst of gunfire. As he lays injured, he reminisces about simpler, joyful moments with his mother, reflecting on times she would toss him into the air like a delicate feather dancing in the wind. This poignant memory emphasizes that even in death, fleeting moments of joy and liberation persist.
