Set in the mid-1960s in suburban Charlotte, North Carolina, the novel opens at the Sunnymede neighborhood pool, where four-year-old Barbara Ann Walters is silently drowning in plain sight. No one notices: not the gossiping neighborhood women, not the roughhousing boys, and not Barbara Ann's own father, who is distracted by the young lifeguard's swimsuit strap. Seventeen-year-old Lorraine Delford, Sunnymede's only female lifeguard, spots the girl and dives in to save her. That evening, her father, Eugene Delford, briefly praises the rescue, but her mother, Betty Delford, scolds Lorraine for the loose strap. The family's preoccupation with reputation over substance sets the tone for what follows.
Lorraine is first in her class and determined to become Mecklenburg High's first female valedictorian. She also dreams of becoming an astronaut, inspired by Alan Shepard's 1961 Mercury spaceflight and President Kennedy's Space Race speech. Her boyfriend, Clint Claiborne, is pleasant but uninspiring; she views him as a safety net and looks forward to his departure for college. Her closest friend is Alan Reynolds, a neighborhood outsider raised by his grandparents after his mother died and his father left. Alan nicknames her "BB" for "brains and beauty," and when she confides her dream of space, he tells her that if anyone can do it, she can.
Before leaving for college, Clint takes Lorraine to an abandoned farmhouse at the end of their street and presents her with an opal promise ring. They have sex for the first time; Lorraine, who has never received any sex education, is carried along by momentum rather than informed choice. In the weeks that follow, she experiences exhaustion, nausea, and missed periods but cannot connect these symptoms to pregnancy due to her sheltered upbringing. She tells Clint over Thanksgiving break. He initially agrees to marry, but days later calls to say he has arranged an appointment with a doctor who will "fix" the situation. Lorraine misses the appointment, and Clint tells her that if she wants to keep the baby, she is on her own.
Betty discovers the pregnancy by feeling the bump beneath Lorraine's clothes and reacts with fury. She has Lorraine use Lysol douches in a desperate attempt to end the pregnancy, which fails and causes a chemical burn. A discreet doctor confirms the pregnancy at roughly five months and provides a brochure for a maternity home that promises "a good beginning." Telling her father proves worse. Eugene declares her aspirations finished, that she is now one of "those girls." Betty devises a cover story, and the family's college savings fund the maternity home. For weeks, Lorraine is confined to her bedroom. The night before departure, she tells Alan through the backyard fence that she is going away, and he promises to be there when she returns.
The maternity home is a decaying eighteenth-century brick mansion run by Miss Mahoney, the housemother and social worker, who establishes three rules: share no personal information, make no friends, and forget this ever happened. Lorraine's father refuses to touch her before driving away. Her roommates embody contrasting responses: Mirabelle, a chatty girl from near Charleston, crochets a blanket for her baby Rose and refuses to sign the relinquishment form, while Denise, dark-haired and guarded, signed hers immediately. Miss Mahoney presents Lorraine's relinquishment form as routine, and Lorraine signs without understanding the implications.
The home's "school" teaches only domestic skills: napkin folding, sewing, and bridge. Lorraine is devastated, having expected real academic instruction. At the town library during supervised outings, she meets Ms. Whiler, a young librarian who becomes her informal tutor after securing Miss Mahoney's permission for three weekly sessions. Ms. Whiler introduces Lorraine to Valentina Tereshkova, the first woman in space, and offers a model of independent womanhood. At around thirty-five weeks, Lorraine panics when the baby stops moving, but Ms. Whiler identifies the rhythmic pulses as hiccups. The relief marks a turning point: Lorraine begins thinking of the baby as a person and questioning whether she can give her child up.
Lorraine inadvertently mentions Mirabelle's collage of baby pictures to Miss Mahoney, who destroys it. When Mirabelle goes into labor, Denise reveals that Mirabelle's pregnancy resulted not from a boyfriend but from her father's sexual abuse. Mirabelle is taken away screaming, and neither Lorraine nor Denise learns what becomes of her or baby Rose. Miss Mahoney then assigns Lorraine a list comparing her ability to parent against that of a married couple. Under the "me" column, Lorraine writes only one entry: "I'm her mom." Ms. Whiler discovers the list and urges Lorraine to let go, but Lorraine has grown determined to keep her child.
When Denise falls down the grand staircase in the predawn hours and is found broken on the landing, the chaos gives Lorraine the chance to steal her signed relinquishment form from Miss Mahoney's office. Days later, Lorraine goes into labor at the library. She confides her plan to keep the baby, but when Ms. Whiler helps her to a car outside, Miss Mahoney is in the driver's seat. The housemother drives in circles around the hospital, refusing to go inside until Lorraine signs a new relinquishment form. She presents a letter purportedly from Betty demanding Lorraine sign, though details suggest it is forged, and promises legal recourse later. In agony, Lorraine signs.
At the hospital, an orderly restrains Lorraine and a doctor drugs her into twilight sleep without consent. She has no memory of the birth. She wakes to learn she has delivered a healthy girl weighing seven pounds, two ounces. A young nurse, unaware of maternity home protocol, brings the baby to Lorraine, who traces every feature of her daughter's face, names her Grace, and sings to her until an older nurse forcibly takes the infant away. Lorraine keeps only a pair of tiny white socks.
Grace's birth weight triggers a crucial realization. Her parents married in November and always told her she arrived two months early in July, but a seven-pound baby is not premature. Betty and Eugene conceived Lorraine out of wedlock, making their punishment of their daughter deeply hypocritical. Back home, Lorraine confronts them; neither denies the truth. Betty reveals she called Miss Mahoney about getting Grace back, only to learn the adoption is final and the promised legal recourse was a lie. They share a rare embrace, and Betty tells Lorraine she is stronger than she knows.
Lorraine decides to put on the girdle her mother provides and face the Sunnymede Sisters, the neighborhood women who regularly gather and gossip, at a gathering. She learns from Clint's mother that he is already dating someone else. The sight of a baby carried by Mrs. Walters, Barbara Ann's mother, triggers Lorraine's breast milk to leak. She flees to the abandoned farmhouse, where Alan finds her. He slides the opal ring off her finger with pomade, and she throws it into the ruins. They dance on the sagging porch to The Rolling Stones on his portable record player, holding each other in silence.
The epilogue jumps to July 20, 1969, the Apollo 11 moon landing. Lorraine sits in a diner studying for a college math exam. She watches a brown-haired girl, roughly four, clutching a toy rocket. When the girl's brother drops it, Lorraine retrieves it and tells her never to let go of what is hers to keep. Alan arrives and tells her that someday she will be the one going to space. For the first time, Lorraine tells him she loves him. He responds that he has always loved her. The novel closes with Lorraine acknowledging that the scars of her experience will never fully fade, but that survival means piecing together new dreams from the remnants of shattered ones.