The Marriage Plot, by Jeffrey Eugenides, is a book that centers on a love triangle between Madeleine Hanna, who is studying literature at Brown University, and Leonard Bankhead and Mitchell Grammaticus. The book takes place in the 1980s, and Madeleine is trying to navigate her relationship with her boyfriend Leonard, while her friend, Mitchell hopes their friendship will develop into something romantic. Madeleine's relationship with Leonard is not without its hurdles, as Leonard suffers from manic-depression.
The story opens on graduation day, and Madeleine wakes up with a massive hangover. She and Leonard have just broken up, and she spent the previous night drinking heavily to forget her woes. Madeleine goes to meet her parents for a pre-graduation breakfast, and when they see Mitchell across the street, they press Madeleine to invite him to join them. She does so, even though her last contact with Mitchell was several months ago, when he accused her of leading him to believe there could be more than friendship between them, when she had no such intention. This he communicated via an angry letter.
Eugenides takes this opportunity to show the reader the history of Leonard and Madeleine’s relationship. When she first came to Brown University, she was studying Victorian literature. Later on in her academic career, Madeleine studied a new literary theory, known as Semiotics. In that class, she met Leonard and they started dating. Madeleine told Leonard she loved him, but his cynical response was unexpected—he told her that her words were meaningless. The book then returns to graduation day, when Madeleine hears that Leonard was hospitalized for a psychiatric breakdown. Still in love with Leonard, Madeleine skips her graduation to sit with him in the hospital and they mend their relationship.
Following Leonard’s discharge from the hospital, he insists that Madeleine keep his mental health struggles a secret. He begins a research fellowship at Pilgrim Lake and they move in together. While visiting, Madeleine’s family finds one of Leonard’s prescriptions, revealing his struggle with mental health. Meanwhile, Mitchell and his friend Larry are traveling through Europe. In Paris, they were supposed to stay with Larry’s girlfriend, Claire, but Mitchell is uncomfortable staying with the couple and ends up getting his own accommodationsm, meeting up with Larry later to continue their trip. Before they leave Paris, Larry and Claire break up.
When in Greece, Mitchell receives a letter from Madeleine. The two had met up in New York and shared a kiss, but in her letter, Madeleine explains that she’s devoted to Leonard. She writes that nothing can ever separate them. Meanwhile, Larry starts dating a Greek man, and he and Mitchell decide to travel separately and reconnect at a later date.
As time passes, Leonard feels more and more dependent on Madeleine. His medication has severe side effects, and he’s also dealing with depression. Despite his doctors’ warnings not to do so, Leonard begins to experiment with his medicine, changing his dosage. This launches him into a manic period, when he proposes to Madeleine. At the same time, Mitchell finds himself in Calcutta, India, volunteering at a home run by Mother Teresa. However, he struggles with some of the tasks assigned to volunteers and eleaves, but not before he sends a letter to Madeleine imploring her not to marry Leonard.
Despite Mitchell’s pleas and Leonard’s mental illness, Madeline marries him. They honeymoon in Europe, where Leonard has another manic episode. He’s hospitalized. While he’s recuperating, he and Madeleine move in with her parents. Meanwhile, she applies to and is accepted at Columbia University for a graduate literature program, so Madeleine starts apartment hunting in New York City. They attend a party with other graduates of Brown University, where Leonard and Madeleine argue. He’s upset because he doesn’t want to rely on her financially. Mitchell is also in attendance. Leonard tells Madeleine that he wants to get divorced and then disappears.
After Leonard leaves, Madeleine returns to the party. Mitchell ends up taking her home and starts living with her family. Together, they discover where Leonard disappeared to—a remote cabin in Oregon. Madeleine’s parents want her to annul her marriage with Leonard, since he’s sick and wants a divorce anyway. While Mitchell is living with them, he and Madeleine have sex. However, they both feel differently toward one another and Mitchell realizes that, while he harbors romantic feelings for Madeleine, she doesn’t love him romantically and only slept with him to help her move on from Leonard. Mitchell asks her if she knows of any Victorian novels in which the other suitor offered to let his love go, so that the heroine could move on with her life; he asks her if she thinks that would be a good way for a novel to end.
Madeleine says yes and the book ends.