Divergent is set in the future, in a dystopian version of Chicago that has been divided into five factions: Abnegation, Candor, Amity, Dauntless, and Erudite. The protagonist and narrator is a sixteen-year-old girl from Abnegation named Beatrice Prior.

The novel opens with Beatrice’s mother cutting her hair. Beatrice is worried about the next day’s aptitude test, which is administered to all sixteen-year-olds and will tell her which of the factions she is best suited for. After the test, she will attend the Choosing Ceremony, where she must decide whether to stay in her family’s faction or leave it behind.

Beatrice is sure that her brother Caleb will stay in Abnegation, which values selflessness and humility above all else, but she is conflicted. She has a strong desire to join Dauntless, the faction whose members value bravery. Trying to ignore her feelings, she goes in for her aptitude test, which is administered by a Dauntless woman named Tori. Tori injects Beatrice with a serum that initiates a series of simulations to which Beatrice must respond. After the test is over, Tori leaves the room looking concerned. When she returns, she tells Beatrice she is suited for multiple factions, meaning she’s what’s known as Divergent. Tori warns her not to tell anyone, and Beatrice returns home wondering what her results mean. At dinner that night, she tries to hide her conflicted feelings from her parents and brother.

The following day, all the families of sixteen-year-olds attend the Choosing Ceremony. Beatrice’s entire family is shocked when Caleb picks Erudite. After some hesitation, Beatrice chooses Dauntless. She leaves the building and jumps onto a train with the other initiates, where she meets Christina and Will, who will become her good friends. When they arrive at the Dauntless compound, a boy named Peter insults her. She responds by being the first person to jump into the Pit, Dauntless’s headquarters seven stories below. After a boy named Four helps her up, she introduces herself as Tris. The initiates proceed to the dining hall and Tris meets Eric, the ruthless head trainer of initiates. The next day, Eric tells the trainees that initiation consists of a three-stage ranking process. Those who rank high enough will become members, while the rest will become factionless. Tris vows to succeed and performs well on the first day of stage one, which involves shooting guns at targets. That night, Christina outfits Tris with flattering clothes and makeup, and she gets three birds tattooed on her collarbone to represent her family.

Next, the initiates must fight each other in an arena and try to knock each other unconscious. When Christina concedes to her opponent, Eric forces her to hang over a chasm in the Pit for five minutes as punishment. The following day, Tris finds that Peter has spray painted the word “Stiff” all over her bed. He also beats her in that day’s fight, sending her to the infirmary. She begins having doubts about her place in her new faction, and her worries intensify during a field trip to the compound wall to learn about Dauntless jobs. Late that night, Eric and Four take the initiates to Navy Pier, an abandoned park in the city, to play capture the flag. As Tris and Four climb a Ferris wheel so they can see where the other team is hiding, Tris realizes she’s starting to like him. She leads their team to victory, impressing Four and angering Eric. The following day, Tris’s friend Al performs badly during a knife-throwing exercise, and Eric orders him to stand in front of the target while others throw knives at him. Tris offers to take Al’s place, and Four throws knives around her head, nicking her ear.

Peter and his friends Molly and Drew continue to torment Tris. After they steal her towel and mock her naked body, she takes revenge by beating Molly up during their assigned fight. Tris finds comfort in her mother’s presence on Visiting Day, but the reunion is marred when Will’s sister accuses Tris’s former faction of hoarding food and goods. Taking Tris aside, her mother asks about her rankings and tells her to convince Caleb to research the simulation serum. The conversation makes Tris realize her mother must have come from Dauntless. Back in the dorm, Al puts his arm around Tris, but she rebuffs him. Later that evening, the rankings show that Tris in sixth place and Peter in second. That night, Edward, who placed first, gets stabbed in the eye, presumably by a jealous Peter. Tris is happy for a distraction the next day, when she gets invited to zip line off the top of the Hancock building with the Dauntless-born initiates.

In the second stage of initiation, the initiates are injected with a serum that induces a fear simulation. After Tris’s first simulation, Four informs her she was able to escape the test much faster than anyone else. Still, she is stressed about the tests and angry at Peter, who’s been distributing Erudite reports accusing Abnegation of corruption. After another trip to the tattoo parlor, she flirts with a drunken Four. During her next simulation, she escapes the hallucination by manipulating it, leading Four to realize she’s Divergent. He warns her not to share her status with anyone. She again talks with Tori, who tells Tris that Dauntless leaders killed her brother when they learned he was Divergent.

Because she’s able to manipulate the simulations, Tris ranks first after stage two, leading Peter to threaten her. One night, as she gets a drink of water in the hallway, she hears Eric talking with an unknown woman about Divergent rebels. Suddenly, she’s attacked from behind and taken to the chasm by Peter, Drew, and Al. One of the boys gropes her chest, and Peter nearly drops her over the edge before Four rescues her. As she recovers in Four’s private room, he advises Tris to feign weakness to stay safe, and they grow closer.

The next day, Tris refuses to accept Al’s apologies, and he commits suicide a few hours later by jumping into the chasm. At his funeral, Eric calls him brave, making Tris angry. She vents loudly about Dauntless’s warped priorities to Four, who warns her that she’s being watched. Frustrated and confused, she blows off steam with her friends by throwing stacks of Erudite reports into the chasm.

During stage three, the initiates are forced to confront all their worst fears in a simulation, but this time everyone knows the scenarios are made up, not just Tris. Tris follows Four up to the fear simulation room, where he sometimes goes to practice facing his phobias. He invites Tris into his simulation, and she learns he has only four fears. One of them is his father Marcus, who is Tris’s father’s colleague. After Tris helps Four through each scenario, he asks her to call him by his real name, Tobias, and they kiss.

The following day, Tobias ignores Tris in public, upsetting her. The initiates must go through a sample fear scenario, and Tris panics during hers, causing Tobias to rebuke her. She slaps him and leaves the Dauntless compound to see her brother Caleb in Erudite. When she finds him, he expresses loyalty to Erudite, angering her. She tells him their mother wants him to research the simulation serum, and then is taken by two men to see Jeanine, the Erudite leader. Jeanine asks probing questions about Tris’s test results, and Tris lies hide her Divergence. Back at Dauntless, when Eric threatens her with punishment for leaving, she and Tobias pretend she was sulking because Tobias rejected her. That night, Tobias takes Tris into the city and shows her that Erudite’s lights are on, a major rule violation. He has discovered that Erudite is planning a war against Abnegation, though he’s not sure how Dauntless is involved.

For the final test, each trainee goes through their fear simulation in front of a panel of judges, with the other initiates watching on screens. During Tris’s simulation, she realizes she needs to feel a sense of control in order to escape. Her creative thinking helps her manage her fears of crows, drowning, burning at the stake, kidnapping, and sex. Lastly, instead of following orders to shoot everyone in her family, she offers to sacrifice her own life. Afterward, Eric congratulates her on passing the test and informs her that all Dauntless members must be fitted with a tracking device. Though she’s suspicious, she allows him to inject her with the tracking serum. Back in Tobias’s room, Tris expresses her worries about sex, and she and Tobias agree they’re not ready for it. They go to the banquet, where Tris learns she’s placed first in the rankings. As she and Tobias kiss, she suddenly realizes the Erudite must be planning to use the tracking devices to control the Dauntless.

Tris doesn’t have time to share her realization with Tobias, and in the middle of the night, she awakens to find everyone leaving the dorm in a trance. Since she’s Divergent, the serum hasn’t worked on her, but she follows the group onto a train. There, she discovers Tobias is also awake, meaning he’s Divergent too. When they arrive at Abnegation, the Dauntless begin shooting everyone in sight. After she stops Eric from killing Tobias, Tris gets shot in the shoulder. She and Tobias are taken to Jeanine, who explains her plot to take over the government. She injects Tobias with a serum that makes him attack Tris. He’s sent away, while Tris is knocked unconscious.

Tris wakes up in a glass box filling slowly with water, just like in her simulations. Before she can drown, her mother appears and saves Tris’s life. Her mother is killed by Dauntless soldiers shortly afterward, and Tris kills Will in the process of escaping. She finds her father and brother hiding with other Abnegation members, including Marcus, Tobias’s father. They treat her wound, then head toward the control room at Dauntless headquarters. Tris leads her family into the Pit, where she finds Peter acting as a guard. Tris forces Peter to lead them to the control room, and her father is killed in the process of helping her. She finds Tobias, still under the influence of Jeanine’s serum, manning the computer program. They struggle to get each other’s weapons, and after she lets Tobias take her gun, she pleads with him to see her. He comes out of his trance and stops the computer program. Taking the hard drive with them, they reunite with Caleb and Marcus, then jump on a train heading toward Amity headquarters. Tris notices that Marcus seems interested in the hard drive and wonders what will happen next.