The story begins with a prologue in which the main character, Rosemary, tells the reader that her actual friends may be surprised to find that she was an energetic and talkative child. She also talks briefly about her sister, Fern, and how her father used to criticize her for talking too much.
The first chapter of the first part starts in the middle of the narrative, in the year 1996 when Rosemary is still a student. Rosemary hints that her parents are dissatisfied with her because she had yet to graduate collage and she remembers fondly her brother Lowell which she hadn’t saw in ten years and her sister Fern who disappeared 17 years ago.
Rosemary is still in collage and in the first chapter she recalls how she meat Harlow during a cold day in winter at the cafeteria. Rosemary witnessed a confrontation that became violent between Harlow and her boyfriend and when the police came, they took Rosemary instead of taking Harlow. To show that she disagrees with their actions, Rosemary throws her plate of food and glass of milk on the ground, in front of the police officers.
The girls are arrested and then placed in the same cell together. Harlow tells Rosemary that she is a drama major and then they spend the next few hours together in prison. When they are released, Rosemary calls her father who agrees to persuade the police to drop the charges if she agrees to go home from thanksgiving. Even though Rosemary is not thrilled by the idea, she accepts.
When Rosemary goes home, everyone avoids talking about her arrest. Rosemary’s parents are both scientists and they both were largely absent from their children lives. The dinner is held at Grandmother Donna’s house and there are other relatives present as well. The family avoids certain topics as to not create more tension but Rosemary’s father can’t stop himself from bragging about Rosemary and her SAT scores. This proves that despite Rosemary’s cold attitude, her family cares deeply about her. Rosemary’s mother also proves her affection for her daughter when she decides to give Rosemary her journals instead of donating them to some research center.
When Rosemary returns to collage, she finds Harlow sitting in her apartment. Harlow admits that she was thrown out by her boyfriend and that she had nowhere to go. Thus, she found Rosemary’s address from the police report and then convinced the doorman to let her in. The next day the manager comes and tells Rosemary that the only reason why he let Harlow in was because he feared for her life. The author suggests however that the manager, Ezra, was seduced by Harlow. The one who is not happy however to see Harlow was Rosemary’s flat mate, Todd. After Harlow left, Todd wondered if maybe they should change the locks on their door.
A few days later, Harlow returns and offers to buy Rosemary a beer. They go together to a bar and there Rosemary tells Harlow that when she was little, she was one day sent to live with her grandparents in Indianapolis without being told why she was sent away. Her stay was uneventful since her grandparents were old people who would just sit all day and watch TV. Rosemary remembers however that she one day tried to walk home to her parents after she jumped on the trampoline and her skirt flew up, revealing her underwear. On her way home, Rosemary knocks on a man’s door who returns her to her grandmother. The next day, Rosemary is returned to her parents and she finds that her mother was having a nervous breakdown and it is because of that Rosemary was sent away.
Towards the end of the fifth chapter, Reg appears but Rosemary is not impressed by him and thinks that he is unintelligent and boring.
When Rosemary returns to her apartment, she finds that he brother came looking for her but gave a false name instead of giving his real name. Rosemary notes how the last time she saw her brother she was eleven years old and how after that she did everything she could to stay away from him. She also reveals that for some reason, Lowell is followed by the FBI.
Rosemary ends the first part of the book by confessing that there is no way of knowing if what she writes is true or not because memories of the past often get influenced by the present and they become modified.
The second part of the novel starts in the year 1979 when Rosemary is five years old and she is taken home by her father. When she wakes up, she sees an unfamiliar room and calls for her father. Her father comes into her room and tells her that they moved into a new home. When Rosemary decides to explore the new house, she discovers only three bedrooms and thus realizes that one of their family members disappeared. Rosemary was happy that she was not the one who was taken away but she was able to see how her sister’s disappearance affected her family. Rosemary’s mother became more distant, choosing to come out of her room only during the night and so Rosemary’s maternal grandmother, Donna, had to come and take care of her. Grandma Donna did not seem to be affected by the fact that Fern disappeared. Grandma Donna always makes sure to leave before Rosemary’s father arrives but he knows that she was there either way. Rosemary’s father began drinking shortly after Fern disappeared and despite not getting along with her brother too well, Rosemary is thrilled when her brother returns home.
Then one day, Rosemary and Lowell together with a friend go on a trip and end up at their old house. Lowell makes Rosemary enter the house through the doggy door even though Rosemary claims that she doesn’t want to see Fern. While Lowell is outside with his friend, arguing, Rosemary’s nanny figures out that she disappeared and the children are found and punished for their actions.
In the fifth chapter, Rosemary reveals that both Mary, her imaginary friend, and Fern were chimpanzees. Rosemary and Fern spent a lot of time with scientists and students and Rosemary felt like she was always competing with Fern.
After Fern disappeared, the family slowly became normal again and Rosemary’s mother snapped out of her state and became once more a loving mother. Still, whenever Fern was mentioned, things got tense and fights would appear in the family. Fern affected in a negative way Rosemary’s behavior and she began to behave like a chimp, which made her the subject of bulling and teasing.
After Fern disappeared, Rosemary began behaving in a destructive manner and she even began to hurt herself because she was left without the ‘’person’’ she grew up from the moment she was born. After Fern disappeared, Rosemary stopped talking the way she used to because she considered it as being worthless.
Lowell also becomes more difficult after Fern disappears because he feels as if his parents stopped loving him as well just in the same way they stopped caring about Fern. Rosemary has trouble making friends and the friend she does make, Dae-jung, end up stop being her friend shortly after meeting her. Lowell tries to act normal and he even enters in a relationship with a Mormon girl. Around the same time, he becomes cold towards Rosemary and then eventually runs away from home without giving any reason why. After a few months, Rosemary finds a note from him telling her that Fern was not taken to a farm like they originally believed.
Lowell’s departure throws the family into turmoil and Rosemary feels alone again and is bullied at school again by her peers. Rosemary’s parents hire private detectives to find Lowell but they are unable until one day the FBI appears at their door and inform the family that Lowell became a suspect in a few fires all over the country and that he is suspected of destroying laboratories where tests were done on animals.
In chapter four in the third part, Rosemary is 15 years old when she meets with Lowell’s former girlfriend and with a student who used to study Fern. The student tells Rosemary that Fern was taken to a farm but rather into a lab where she was put to live with other chimps. When Lowell heard about this, he felt enraged because the people in the lab put Fern into a cage. Despite what she found, Rosemary decides to remain quiet and didn’t bring the subject during the family dinner.
When she was old enough, Rosemary left for collage and refused to talk about her family and about the things her family had done. Rosemary is unable to make friends because she is too quiet and refuses to reveal things about her family and parents. During her time in collage, Rosemary had two flat mates, Scully and Todd but she was unable to connect properly with any of them.
Rosemary feels strangely attracted by Harlow who is wild and uncontrollable. When Rosemary returns to collage, she fears that her brother will appear and then she decides to investigate his involvement in cases of arson. Rosemary thinks that maybe her brother joined the Animal Liberation Front and reads about cases of animal cruelty and how the ALF tried to save the animals. It is then when Rosemary decides to read her mother’s journals but herself unable to do it because the airline lost the suitcase where the journals were.
Rosemary attends a lecture about the behavior of the chimps and she has a panic attack during the lecture. The lecturer analyzes the behavior of chimps and how they are just like humans when it comes to sexual violence and violence in general. The lecture leaves Rosemary feeling unsure of herself and then she starts searching about what happened with the chimps that were raised as humans.
After the lecture, Rosemary meets with Harlow and Reg and they get drunk and high in a public space. The three continue to go from one bar to another until Rosemary is arrested by Officer Haddick and taken to jail for her behavior. Reg took the two girls out of jail and then took Rosemary home where she spent a restless night.
Rosemary leaves her room to go look for the things she has lost during the time she was drunk and when she returned she found that Lowell came to the apartment and that he and Harlow went to have dinner and that she should go there as well. Thus, Rosemary gets dressed and leaves for the restaurant where Lowell and Harlow were.
At the restaurant, Harlow flirts with Lowell and tells him about all the adventures Harlow and Rosemary had together. Rosemary is furious that she didn’t got the chance to talk with her brother but then he shows up in the middle of the night and they go to a diner where they talk until well into the morning. Lowell tells Rosemary that he is a vegan and that he studied how animals were abused all in the name of science. Lowell told Rosemary that after Fern disappeared he found her in a laboratory locked in a cage with other three chimps. Fern was confused and was also violent when Lowell approached her but there was no way Lowell could have taken Fern away from the lab. Lowell continued to keep tabs on Fern and he had a man inside the lab who made sure that Fern was alright. Lowell also reveals that Fern had three children and that she began teaching sign language to one of them, a chimp named Hazel. Before he leaves, Lowell tells Rosemary that it was her job to take care of Fern from that point on.
Rosemary returns to her dorm and she continues to think about a way she could save Fern and Hazel but reaches the conclusion that she will not be able to save both chimps. Rosemary investigates accounts of experiments done on animals and also reads about the ALF. Harlow meanwhile moves in the same apartment building as Rosemary but instead of being thrilled, Rosemary is annoyed because Harlow keeps talking about Lowell and even enters a depressive stage when Rosemary tells her that Lowell will not be coming back.
A few days before Christmas, a police officer arrives at Rosemary’s door and she is taken in for interrogation but the police officers claim that she is not under arrest. While she waits in the holding cell, Rosemary remembers the time when Fern became uncontrollable, killing smaller animals than her and hurting Rosemary. Lowell told her to be quiet but Rosemary ended up telling her mother about what was happening.
Rosemary is let go when Todd arrives with her mother. Todd’s mother tells Rosemary that Ezra broke into a facility where chimps were held and claimed that he had an accomplice. Believing Rosemary to be the accomplice, she was taken in but released when Ezra admitted that Harlow was the one who helped him. Todd and Kimmy theorize that maybe the reason why Harlow did what she did was because Lowell told her but Rosemary refuses to believe such a thing.
Rosemary goes home for Christmas but she doesn’t tell her parents about the fact that she was visited by Lowell. After Christmas passes however, Rosemary tells her parents about Lowell and also about her feelings of guilt. Her parents start crying and assure her that she was not the reason why Fern was sent away. Instead, Fern became too dangerous as she grew and she was violent not only towards Rosemary but towards the other students studying her as well. Because of this, they could no longer keep Fern.
Ezra is imprisoned for nine months but no one can find Harlow and when Harlow’s parents come and visit Rosemary, she finds that everything Harlow told her about her parents was a lie. Rosemary goes on with her life, thinking about what she will do after finishing collage. She then dates Reg for half a year but then they break up after fighting too much.
In 1998 Rosemary’s father dies but still Lowell doesn’t show up. In the same year, Rosemary receives the lost suitcase and discovers that inside them there were pictures of her and Fern and baby books. Rosemary talked with her mother about Fern and learned that her mother loved Fern just as she would love her biological child. Fern’s mother was killed and she was bought from poachers in an attempt to save her.
The story them moves a few years forward in 2012 when Rosemary was working as a kindergarten teacher and her mother was a volunteer at the lab where Fern and Hazel were being held. Rosemary plans to raise enough money to build a sanctuary for Fern and even though she knows that Fern will never be considered safe enough to be let to roam free, Rosemary is certain that the chimp will be more happy in a sanctuary than in a lab.
