Thirteen-year-old Henry lives alone with his mother, Adele, in Holton Mills, New Hampshire. His father left years ago for his secretary, Marjorie, and now lives nearby with Marjorie, her son Richard, and their baby daughter, Chloe. Adele rarely leaves the house, ordering everything by catalog and subsisting on canned goods and frozen dinners. Henry does the grocery shopping, the banking, and most of the errands. It has been a long, uneventful summer, and he is consumed by curiosity about girls and sex but has no one to talk to.
On the Thursday before Labor Day, Adele reluctantly drives Henry to Pricemart to buy school pants. A tall man approaches Henry in the store, bleeding from his leg and head. He wears a red employee shirt labeled "Vinnie," though his real name is Frank, an escaped convict. He claims he fell out a window and asks if Adele might give him a ride. Frank conceals his injuries with a cap and vest grabbed off the racks, introduces himself to Adele, and joins them in the car.
Once home, Frank tells them the truth: He escaped from the state prison by jumping from a hospital window after an appendectomy. The television news confirms his story and adds that he is wanted for murder. Henry is frightened but excited, sensing something is finally happening. He does not call the police. Frank ties Adele's wrists and ankles with her own silk scarves to create the appearance of a hostage situation, protecting her legally if he is found. He handles her with surprising gentleness, and Adele shows no fear. That night, Frank makes chili and feeds her spoonful by spoonful, blowing on each bite to cool it. Henry, struck by the tenderness of the scene, takes his dinner to the living room.
Over the following days, Frank transforms the household. He changes the furnace filters, rotates the car's tires, does laundry, and irons. He teaches Henry to grip a baseball, and for the first time Henry catches and hits balls. Adele comes downstairs Friday morning in a flowered blouse with earrings, lipstick, and perfume, looking younger and happier than Henry can remember. Frank folds the scarves away, telling Adele he will not tie her again. When a neighbor drops off ripe peaches and warns about the escaped prisoner, Henry says nothing. Frank teaches Henry to make pie using the technique his grandmother taught him: combining lard and butter for flakiness, using ice water sparingly, and never overhandling the dough. That Friday night, Henry hears Frank and Adele climb the stairs together and, through the thin wall, the unmistakable sounds of lovemaking.
The novel gradually reveals the losses that shaped Adele. She was once a gifted dancer who met Henry's father at a wedding. They traveled the country selling hot dogs and dreaming of becoming TV dancers. After settling down, Adele endured an abortion her husband pressured her into, three miscarriages, and finally a stillbirth: a girl named Fern, killed by a twisted umbilical cord. Afterward, the sight of pregnant women and babies became unbearable. She stopped leaving the house, stopped dancing, and withdrew from her marriage.
Frank's history also emerges over the weekend. His parents and baby sister died in a car accident when he was seven, and his grandmother raised him on a farm. After serving in Vietnam during the Tet Offensive, a devastating series of battles in 1968, he returned home traumatized. A local woman named Mandy moved in and announced she was pregnant. Frank fell in love with his son, Francis Junior. But Mandy started an affair and admitted the baby was not Frank's. In a flash of rage, Frank pushed her; she fell, hit her head on a granite step, and broke her neck. Upstairs, his grandmother had a fatal heart attack while bathing Francis Junior, and the baby drowned. Mandy's sister testified that Frank killed his own child. He was convicted of murder and sentenced to 20 years. He had served 18, with only two years left before parole, when he jumped.
On Sunday, Henry meets Eleanor at the library, a sharp-tongued 14-year-old with an eating disorder, recently sent to live with her father. She identifies Henry's situation as sexual brainwashing, comparing it to the story of Patty Hearst, the newspaper heiress kidnapped by radicals in the 1970s. Eleanor urges Henry to call the police and collect the $10,000 reward. Henry is conflicted: He likes Frank but feels increasingly excluded from the intimate world Frank and Adele have created. That evening, Adele tells Henry that Frank has proposed and they plan to flee to Canada under new identities. Henry, who feared they would leave without him, is relieved when Adele insists she could never live without him. Frank asks Henry's permission, and Henry agrees.
The plan unravels. Henry insists on bringing his hamster, Joe, but Adele says the animal could jeopardize their border crossing. Henry explodes, using profanity for the first time and accusing his mother of caring only about sex with Frank. On Wednesday morning, the day they plan to leave, Henry finds Joe dead from the heat. Distraught, he walks to his father's house and drops a farewell letter in the mailbox. A police officer finds him on the road and drives him home. Adele's former friend Evelyn stops by with her son Barry, a boy who uses a wheelchair and has limited speech; Barry spots Frank inside and calls out his name, the first intelligible word Henry has ever heard him speak. At the bank, Adele withdraws her full savings of $11,300. When they return, Frank tells them Henry's father has read the letter and is coming.
Sirens, police cars, and a helicopter converge on the house. Frank ties Adele to a chair and loops rope around Henry's chest, a deliberately inadequate restraint to support the hostage story. He walks out with his hands raised, is handcuffed on the lawn, and mouths Adele's name before the police car door closes.
Frank confesses and waives his right to a trial so that Adele and Henry will face no charges. He receives 25 years. Adele drives to the capital to tell the prosecutor Frank never held them against their will and that they planned to marry, but the prosecutor warns that she could be charged for harboring a fugitive and Henry as an accomplice. Faced with these threats, Adele relinquishes custody of Henry to his father. Henry moves in with his father's family. On a bike trip to Vermont, his father admits for the first time that losing the babies destroyed Adele and that he left because he could not handle her grief. After living with his father for most of seventh grade, Henry moves back to Adele's house and makes the baseball team, silently repeating Frank's advice every time he bats.
A year or two later, Henry confronts Eleanor after rescuing her dog from traffic. He realizes she was the one who called the police about Frank. She admits she just wanted something to happen, and both of them cry.
The novel's final section leaps forward nearly two decades. Henry, now 31, is a pastry chef whose specialty is pie made with Frank's crust technique. After a food magazine profiles his work, Frank writes from prison, having seen the article. He asks whether Adele might be willing to hear from him. Henry writes back immediately, telling Frank she still lives at the same address. After his release, Frank reconnects with Adele, and they settle together in Maine. Henry marries his girlfriend, Amelia, a kindergarten teacher, and they have a daughter. When she cries during the long drives north, Henry pulls over and holds her against his chest, following Frank's advice about tending to a baby with patience. Every time they arrive, the lights are on and the door is open, Adele standing there with Frank beside her. Her first words are always the same, asking whether they brought the baby.