The following version of this book was used to create this study guide: Unferth, Deb Olin. Barn 8. Minneapolis: Graywolf Press, 2020.

The novel opens with 15-year-old Janey Flores arriving in Iowa to meet her father for the first time. Janey's mother, Olivia Flores, had just revealed her father's name and location and, angry that this information had been kept from her for so long, Janey hopped on a bus from New York to go see him. Upon arrival, Janey and her father clash, but Janey insists on staying and getting to know him better. A few weeks later, after a terrible fight, Janey calls her mother to ask for a return ticket home. She cannot reach her, and moments later she receives a call alerting her that her mother has been in a fatal car accident. Janey's father is awarded custody of her. Five years later, Janey is still grieving and depressed. Her father suggests she apply for a job with his employer, the USDA. The open position involves auditing (checking health and safety standards at) the local egg farms, and the person in charge of hiring, Cleveland Smith, once knew Janey's mother.

When Cleveland, 34, was a child, Olivia Flores was her babysitter, and Cleveland still thinks of her as the epitome of beauty, intelligence, and sophistication. She is excited to hire Olivia's daughter, but she and Janey do not immediately get along. One day, while leaving a farm, Cleveland sees a hen that has escaped one of the barns. Rather than return it, she puts it in her car and takes it to the local animal rights organization. She receives an angry email from the organization in response, but she begins sneaking onto the farms at night and taking more hens to drop off there. One night, Janey is sitting outside of Cleveland's house in her car and she sees her leave. She follows her to a farm and watches Cleveland take hens. The two begin engaging in this activity together. When they receive an email stating that the animal rights organization employee, Dill, has been fired, they begin taking the hens to the farm where he lives.

Dill is recovering from a drug addiction, and in addition to being recently fired, his husband is divorcing him. Janey and Cleveland come to him with an idea—they wish to remove all of the hens (one million) from Happy Green Family Farm. They ask for his help because they know he is a friend of Annabelle Green, the black sheep daughter of the Green family who is also an animal rights activist. Dill sends Janey and Cleveland to the original Green Farm, now a chemical waste contamination site due to an accident at a nearby weapons factory years earlier. This is where Annabelle is living, off the grid. This is revealed through an interview Annabelle is giving to two investigators after the fact. She is willing to help, and enlists the expertise of her ex-husband, Jonathan Jarman Jr., who is an engineer. Jonathan is not happy to hear from Annabelle because he is still in love with her, despite the fact that he has a new girlfriend.

Jonathan, Annabelle, Dill, Janey, and Cleveland formulate a plan for the hen heist, which would require at least 200 activists and 60 trucks for transporting the animals. They contact every activist they have ever worked with and recruit all the help they need. One of these activists is a man called Zee; he would one day marry Janey Flores. The plan hinges on Barns 7 and 8 being emptied of hens by the Greens' staff days before, as these two barns were being decommissioned. Annabelle goes to Green Farm the night before the heist to check these barns, but she is caught by the security guard and flees.

The heist unfolds perfectly until Dill goes to check Barns 7 and 8 and discovers that Barn 8 is full of hens. He comes back and tells the others, at which point a couple of renegade activists find a gas can and set the barn on fire. The activists flee. Annabelle, Dill, and Zee go to the original Green Farm, where Annabelle has sent two trucks full of hens. The fire brings the authorities to the other farm, and Janey and Cleveland are arrested. Zee is also arrested on his way back from the original Green Farm. Annabelle and Dill release the hens onto the land surrounding the farm. The police arrive and see Annabelle on the roof of the barn. She falls through it. It is revealed that the conversation she has been having with the two interviewers interspersed throughout the novel is actually happening in her mind while she is comatose and in some sort of purgatory. The interviewers give her the option of dying or returning to the world. She hears Jonathan calling to her from her hospital bedside and decides to return.

After being arrested, Zee is placed next to Janey in the police station and he immediately begins to woo her. Years in the future, they are married and have a child together. The baby dies at three months old and Janey returns to her father's apartment, locking herself in her old bedroom. Zee calls Dill for advice and Dill tells him to go to the apartment and stay there until she is ready to come out. It is Cleveland who finally convinces her to do so. Zee and Janey have another baby, whom they call Olive, and Cleveland helps raise her, telling her all about her grandmother Olivia.

A park ranger assigned to the area around the original Green Farm discovers the hens that had been released there and decides to buy a few roosters to introduce to the population. The hens and the roosters reproduce, and these chickens remain on the land for thousands of years, even outliving humankind.