The novel tells the story of TifAni "Ani" FaNelli, gradually revealing information about her past while alternating between events occurring in the present. At the start of the novel, Ani seems to have a near-perfect life. She lives in New York City and writes for a well-known women's magazine. Ani is engaged to a wealthy and handsome man named Luke Harrison, and maintains a fashionable and glamorous appearance. With her upcoming wedding only a few months away, Ani is very close to achieving her long-time goals of affluence and life amidst the upper-classes. This is especially important to her because she grew up lower middle-class, and has worked very hard to groom herself into someone who can imitate a different social status. However, under her persona of poise and success, Ani is often angry and embittered. She and Luke have significantly different values, and she often feels that she cannot be her true self around him.
It is gradually revealed that Ani lived through traumatic events as a teenager. When she was 14, in the autumn of 2001, Ani began attending a prestigious private school called the Bradley School. Ani was eager to fit in and make friends with the other students, especially since most of them were wealthier than her family. In particular, Ani wanted to be accepted by a clique of popular students including Hilary, Olivia, Dean, Peyton, and Liam. Gradually, it seemed that Ani might be earning their acceptance; however, about a month after beginning at the Bradley School, Ani was lured to a party where a group of boys (including Dean, Peyton, and Liam) got her drunk and then repeatedly raped her.
Shortly after the gang rape, Ani was attacked by Dean a second time at a party at Olivia's house. Ani confided in her English teacher, Mr. Larson, about what happened, and he wanted her to tell the school authorities. However, Ani decided not to do so, and Mr. Larson was fired from the school. Ani was socially ostracized, and began spending a lot of time with a student named Arthur Finnerman, who was often bullied, and who hated Dean and the others. Ani and Arthur would sometimes joke about how they hated the other students, and even about killing them. One day, Ani and Arthur got into a fight because Arthur accused her of still seeking approval from the popular students even though they had done such terrible things to her.
The next day, Ani was at school when a bomb exploded. Arthur and Ben, a boy who had formerly attended the Bradley School and who had also been brutally bullied, had planned a school attack in which they brought guns to school and shot the students who had tormented them. In the chaos of the attack, as Ani tried to flee the school, she encountered Arthur and Dean; Arthur offered Ani his gun and the chance to shoot Dean, but then changed his mind and shot Dean himself. Ani eventually killed Arthur with a knife, and then fled from the school. In the end, five students, including Liam, Peyton, and Olivia, were killed in the attack; Ben killed himself as well. Dean survived, but was left paralyzed due to his injuries.
After the attack, many people speculated that Ani might have been involved, since she was a social outcast who was close friends with Arthur. Dean also told many people that when Arthur offered Ani the gun, she reached for it. In order to protect herself, Ani never told anyone about having been raped. She became obsessed with becoming wealthy, beautiful, and successful, and this ambition drove her through her adult life.
In the present day storyline, Ani films a documentary about the events at the Bradley School while also preparing for her wedding. She also reencounters Mr. Larson, who helps her to see that she has been strong and resilient. The process of filming prompts her to reflect more on the events that happened when she was a teenager, and she becomes increasingly angry about how she was treated. She also gradually realizes that she does not like or respect Luke, and does not want to spend the rest of her life lying and pretending. During the documentary filming, Ani demands that Dean explicitly admit that he and the other boys raped her; she secretly records him making this statement. Ani shares this recording with the documentary crew so that they can reveal the full story of what happened to Ani before the attack. She also abruptly calls off the wedding right before it takes place. At the end of the novel, Ani finally feels authentic and confident because she is no longer lying and hiding.
