Kim stands outside a Chinatown bridal shop and watches a five-year-old girl in the window. Seeing the girl, Kim is reminded of why she didn't want this life for her child—this little girl will spend her life working in a factory. When the girl's father walks in, Kim feels as though her heart is breaking.
Kim and Ma immigrate to the U.S. when Kim is eleven. Aunt Paula and Uncle Bob drop Ma and Kim off at their new apartment, which is in a rundown neighborhood. They're both shocked to see that the apartment is filthy and infested with bugs. Kim believes that Paula did this on purpose, and that she must know how bad the apartment is. No longer requiring Ma's services as a caretaker for her sons, Nelson and Godfrey, Aunt Paula creates a job for Ma at her garment factory. Kim suspects this isn't actually a favor, though Ma reminds her that they owe Paula a huge debt. Ma tearfully tells Kim that she'll need her help at the factory.
Ma and Kim are very late for Kim's first day of school. Her school is in a neighborhood that's much nicer, thanks to Aunt Paula's suggestion that Kim use a different address as her official one. After spending the day struggling with the cultural differences between Hong Kong and American schools, Kim's teacher, Mr. Bogart, accuses her of cheating on a quiz. After school, Ma teaches Kim how to take the subway to the factory in Chinatown, which is loud, hot, and noisy. Before beginning work, Ma asks Aunt Paula about getting a different apartment. Paula insists they'll get a new apartment soon and points out the thread cutting table. She explains that kids start at there and then return to the table as old ladies. Kim also meets a boy named Matt. Kim understands that she, Matt, and the other factory kids aren't real employees; because employees are paid by the piece, bringing one's children is necessary to get more done.
Kim skips school for several weeks to help in the factory. Ma tells Kim that she needs to be careful hanging out with Matt, because she could end up spending her entire life in the factory, as he likely will. Kim understands that she needs to use her intelligence to save herself and Ma, so she decides to return to school on Monday. At school, she becomes friends with a white girl named Annette. When Kim mentions that she works at a factory, Annette returns the next day and insists that can't be true—her father told her about child labor laws, so Kim must be lying about working. Kim vows to keep that part of her life secret. When Mr. Bogart assigns a diorama, Kim and Annette decide to work together at Annette's house. Kim is in awe of the heat, the housekeeper, and Mrs. Avery's kindness. Ma forbids Kim from going over to Annette's again, insisting that they won't be able to repay the debt by inviting Annette over.
Shortly after the Western New Year, Ma and Kim discover faux fur in a dumpster. With it, Ma makes sweaters and robes, and she and Kim are finally warm. When the Chinese New Year arrives, Ma and Kim pray together for their future. They learn a week later from their neighbor Mr. Al that their block is going to be demolished. Ma believes that this means that Paula will move them, while Kim thinks that it's more likely that Paula will never fix anything. When Ma brings up the apartment again with Paula, Paula insists they need to work harder. To combat this, Kim dedicates herself to learning English. Kim fears she's ruined everything when she engages in a fight with Luke, the school bully. Mrs. LaGuardia, the principal, pulls Kim out of class the next day. Kim thinks she's going to be expelled, but Mrs. LaGuardia encourages Kim to think about a private school given her high scores on her standardized math test. Kim suggests she'd like to go to Harrison Prep, where Annette is going next year. Mrs. LaGuardia makes an appointment for Kim to visit the school. Kim goes alone. She considers turning back when she sees the campus and the students, as she knows she and Ma can't afford it. Kim has an appointment with Dr. Weston in which she's tested orally on math, and then she tours the school. When she returns to Dr. Weston's office, she insists the school is too expensive and leaves.
Ma takes the morning off work to attend Kim's graduation ceremony. At the ceremony, Kim is shocked to learn that Harrison Prep is granting her a full scholarship. Later, at the factory, Paula has the letters from Harrison Prep and is angry that Kim applied without her permission. Over the summer, Annette shows up at Kim's house once, though Kim pretends to not be home.
Kim's first day at Harrison Prep is exhausting. She knows she's in trouble when she learns she has to change in a locker room for gym. All the other girls have store-bought underwear, while Ma still makes Kim's. Kim works in the library after school, and when she arrives at the factory, she asks Ma for new underwear. Ma insists that good girls don't look at other girls' underwear. A few weeks later, the school bully, Greg, and the popular girl, Sheryl, start teasing Kim about her underwear. Ma agrees to buy Kim underwear and a bra.
Aunt Paula invites Ma and Kim for dinner, and Nelson baits Kim into admitting that she's doing poorly in school. However, Kim improves rapidly. She devours all the reading material she can and does well in math, though her one wish is to be liked by her peers. During an important science test, a girl named Tammy drops a note near Kim. Kim picks it up thinking it's a friendly note, but Mrs. Reynolds intercepts and discovers that the paper contains notes on the test material. She accuses Kim of cheating and takes her to Dr. Copeland's office. A boy named Curt advocates for Kim's innocence. Kim does extremely well on the test while Tammy fails, and Mrs. Reynolds seems convinced of Kim's innocence. Kim keeps this a secret, as she's embarrassed that she wanted to be liked badly enough to pick up a note during a test.
Over the summer, Kim cuts down the time it takes her to bag skirts to seven seconds per skirt. One afternoon, she and Matt flirt, and she admits she's never seen the Liberty Goddess. As Matt suggests they go, a man named Mr. Pak gets his hand stuck in a steamer. After this, Paula cuts Ma and Kim's pay and moves Matt to the steamer, which enrages Matt's mother, Mrs. Wu. Ma, Matt, and Kim go to Times Square and to see the Liberty Goddess on Sunday, and Kim feels as though she's truly in America.
When the school year starts, Kim continues to do well enough to make Dr. Copeland suspicious that Kim is cheating. She explains that Kim will take an oral exam to prove her innocence. She studies hard, though she discovers that the magazine Car and Driver is an excellent escape. In one magazine, she finds an article about a motorcycle that Matt's disabled little brother, Park, loves. She reads the article to Park at work one day, disproving Matt's insistence that Park is deaf. Kim manages to pass the exam with flying colors. Not long after, Matt invites Kim to come with him to meet Matt's father. Matt's father spends his days gambling, and Kim recognizes that this is Matt's shameful secret.
By tenth grade, Kim is one of the school’s best students. She continues to refuse social invitations, as she knows she can't return them. She also becomes increasingly attracted to Matt, though she doesn't voice her feelings. When Matt begins dating a young woman named Vivian, who is perfect in every way, Kim is heartbroken. Meanwhile, Curt breaks his leg and asks Kim for help with his grades. He's not secretive that she helped him, which boosts Kim's popularity and means that boys begin to take an interest in her. Kim fools around with boys whenever she can and loves the freedom she has with her body.
That winter, Ma and Kim's stove breaks. After a Chinese man attempts to take advantage of them, a man from the gas company is able to fix it. Matt drops out of school to work full-time, while Kim begins taking classes at a local university. Kim remains in love with Matt, and when they end up locked in a restroom together during an inspection, they kiss. Matt insists he'll never be good enough for her, which shatters Kim.
Curt invites Kim to a party to thank her for her tutoring, and Kim lies to Ma so she can go. At the party, Kim smokes marijuana for the first time and begins a physical relationship with Curt, which continues into senior year. Dr. Weston helps Kim apply to Yale and finally, Ma and Kim pay off their debts to Aunt Paula. Paula still becomes angry every time she learns that Kim is doing well in school. Kim also learns that Mrs. Wu is ill and can barely work anymore. One afternoon, as Kim is studying for her naturalization exam, Annette shows up unannounced. She's aghast at Kim's living conditions and insists they need to speak to her mother, who's a real estate agent. A month later, Kim meets with Mrs. Avery about an apartment in Queens with heat and no pests. Kim and Ma have the money; they just need a character reference for Ma.
In March, Matt comes to Harrison and sees Kim with Curt. Matt tells Kim that his mother died. They go to Kim's apartment and have sex, though they decide to use two condoms. After Matt leaves, Kim discovers that the condoms broke. Not long after, Aunt Paula calls Ma and Kim to her office to open two letters from Yale. Aunt Paula is furious, especially when she learns that one letter is an acceptance letter and the other offers Kim a full-ride scholarship. Ma and Kim finally break their ties with Aunt Paula, and Mrs. Avery offers to provide Ma's character reference. That afternoon, Matt takes Kim out on a date and they discuss their future. She tells him about her acceptance to Yale, but Matt insists he wants to stay in Chinatown. They spend a few happy weeks with each other, though Matt continues to insist that Kim shouldn't go to school. Kim soon discovers she's pregnant and believes she can't tie Matt down with a baby.
In the epilogue, Kim is a pediatric cardiac surgeon. She recounts seeing Matt's daughter in the bridal shop window. When she realizes one of her patient's fathers is an old friend of Matt's, she asks him to pass her card to Matt; Matt shows up at the hospital a week later. She and Matt cry as he admits that he knew she had an abortion. She gives him a ride home and sees him with Vivian, who's pregnant. Kim rides home in tears. When she gets home, the reader learns that her twelve-year-old son, Jason, is the spitting image of Matt. Kim thinks about her decision to have Jason and not tell Matt. She now lives in a big house and was able to buy Ma a piano. Kim recognizes that in keeping Jason a secret she's depriving him of his father, but thinks she couldn't have made any other decision.