Flight Behavior tells the story of Dellarobia Turnbow, a twenty-eight-year-old housewife living with her husband, Cub, and two children, Preston and Cordelia, in Feathertown, a fictional town located in rural Tennessee. Dellarobia feels trapped by her role as a housewife and her marriage to Cub, who she was forced to marry after accidentally getting pregnant at seventeen. Dellarobia’s frustrations are further intensified by the tense relationship she has with her in-laws, Hester and Bear Turnbow. Because Cub continues to work on his parents’ farm, Dellarobia and Cub continue to live on the Turnbow family’s land, forcing Dellarobia to continuously see Hester and fall under her critical eye.
Dellarobia, intent on beginning an affair with a local man named Jimmy in order to escape her unfulfilling marriage, hikes out to a mountain on the Turnbow family’s property in order to meet with Jimmy. On her way there, she comes across a breathtaking sight: a large blur of orange, almost like fire, hovering above the mountain. Dellarobia takes this as a sign for her to turn back and abandon her plans, instead returning home and telling her family about what she saw. Upon returning to the area, Dellarobia and Cub discover that the blur is actually a colony of monarch butterflies.
The news of the butterflies soon spreads and Dellarobia is hailed as a visionary after she lies at the local church and says that she came upon the butterflies due to a dream she had. Journalists, tourists, and religious fanatics flock to the mountain. However, the threat of destruction looms on the horizon after Bear signs a contract to have loggers come and tear down the trees that provide a new habitat for the butterflies.
One day, an ecologist named Ovid Byron arrives. He explains that he studies the monarch butterfly and wishes to conduct extensive research on the monarchs that have now inexplicably gathered on the Turnbow farm. He informs Dellarobia that the butterflies are a warning sign; their migration pattern was disrupted after a torrential flood—a climate change-induced natural disaster—hit their original habitat in Mexico. Tensions rise between Ovid and local journalists after a reporter named Tina tries to tamp down Ovid’s explanation of the grave circumstances surrounding the butterflies’ arrival.
Dellarobia’s frustrations within her marriage mount as the differences between her and Cub are brought into clearer view by Ovid’s arrival. Ovid asks Dellarobia to help out as a research assistant, giving her a way of earning money for the first time in years and granting her a new sense of freedom. Dellarobia finds herself developing a crush on Ovid, which later allows her to realize that she cannot stay with Cub due to their incompatibility. A conversation with Hester in which Hester reveals that she, too, married Bear quickly after having a child, also helps Dellarobia see that she doesn’t want to end up like Hester—trapped in a marriage with someone who cannot love her in the way that she needs.
Although the arrival of Ovid's wife Juliet curbs Dellarobia's hopes of having a relationship with Ovid, witnessing Ovid and Juliet further helps Dellarobia realize that she and Cub rushed into a marriage too fast after her first pregnancy. The life that Cub can give their children is not one that Dellarobia wants; where Cub is content helping out on his parents' farm and continuing to live in Feathertown, Dellarobia wants to give Preston and Cordie a chance to pursue their curiosities and fulfill her own dreams of getting an education. Dellarobia decides to leave Cub and return to school in order to get a college degree.
