David Moran, a 41-year-old man who works on Wall Street, narrates from the present day, looking back on the summer of 1958, when he was 12 years old. He situates the events in 1950s suburban America, a period of repressions and secrets, and addresses the story directly to Ruth Chandler, the woman at its center.
David lives on Laurel Avenue, a dead-end street bordered by woods, where every family but one has children. The children call themselves the Dead End Kids. One afternoon at the brook behind the houses, David meets Meg Loughlin, a red-haired girl older than he is. She and her younger sister Susan are staying with the Chandlers next door; Ruth Chandler is their second cousin. David learns that Meg and Susan's parents both died in a car accident. Susan broke nearly every bone from the waist down and uses leg braces and arm crutches. Meg takes on a heroic quality in David's eyes.
Ruth is a charismatic, profane presence among the neighborhood children, generous with snacks and beer and colorful stories. Her three sons are Donny, Willie Jr., and Ralphie, nicknamed Woofer. In the basement sits a bomb shelter her ex-husband built: a small concrete room behind a heavy meat-locker door. Meg tells David she does not like it.
David and Meg ride the Ferris wheel at the local carnival. She wears her dead mother's wedding band and speaks of missing her parents. When David asks how she likes living with the Chandlers, she says Ruth is "kind of funny sometimes" but leaves it at that.
The first signs of trouble emerge gradually. Ruth screams at Susan for minor mistakes and humiliates Meg for refusing to help burn tent-worm nests from her trees. Meg confides to David that nothing she does is good enough. She paints David a watercolor, and when David presents it to Ruth as a gift from Meg, Ruth refuses it and warns Meg that any "slutting around" will mean consequences. That night, David hears shouting from the Chandler house and sees Meg struck so hard she falls out of view.
Ruth begins withholding food from Meg. When Meg refuses to submit to Ruth's demands, Ruth enlists her sons to hold Meg down and punches her in the stomach. She tells David it is a "domestic dispute" and none of his business.
Ruth establishes vicarious punishment: Whenever Meg disobeys, Susan receives a belt-whipping while Meg watches. David recognizes that Ruth is playing a version of The Game, a ritual the neighborhood children played the previous summer in which a captured player was tied up and subjected to whatever the others chose. An adult running it makes the cruelty feel less forbidden.
On the Fourth of July, Meg approaches Officer Jennings at the fireworks and tries to report Ruth's abuse. The officer is skeptical, suggesting Ruth is within her parental rights. When Jennings visits the Chandler house the next evening, he takes no action. Ruth decrees that Meg can never leave the house alone. The neighborhood children's admiration for Meg curdles into contempt. David stops worrying about her and thinks, "Let it go where it goes."
Where it goes is to the basement. Ruth confines Meg in the bomb shelter. The Chandler boys body-slam her against the concrete wall while Ruth watches. They hang her from nails in the ceiling beams by her wrists and strip her with a pocketknife. Ruth establishes a rule: No one may touch Meg. David acknowledges his own corruption, his sense of power at not being the victim.
The shelter becomes a gathering place. Eddie Crocker, a volatile boy from up the street, escalates the violence, beating Meg and dunking her head in scalding water. His sister Denise Crocker and other children drift in to watch. Ruth's physical and mental health deteriorate. She delivers rambling monologues about the "Curse of Eve," insisting that female sexuality is women's fundamental weakness, and burns Meg with cigarettes and matches.
David struggles with his conscience. He asks his father whether it is ever okay to hit a woman and receives an ambiguous answer. One night he stands over his sleeping mother, wanting to confess everything, but cannot speak.
Ruth permits Donny to rape Meg. Afterward, she announces they will carve words into Meg's flesh. Each participant takes a letter, using a heated sewing needle to burn and cut obscenities across Meg's abdomen. David tries to object, but Willie holds a carving knife to his throat.
Ruth proposes a final act: burning Meg's clitoris with a heated tire iron, citing practices of female genital cutting as justification. David breaks for the stairs and runs. Eddie tackles him, and they drag him back and tie him up. He is forced to remain present for what follows, which he refuses to describe.
David, Meg, and Susan are locked together in the shelter. Susan reveals that Meg's earlier escape attempt failed because Meg went back to carry Susan out, and Ruth caught them. Susan also reveals that Ruth has been sexually molesting her, which drove Meg to attempt the escape. Meg drifts in and out of consciousness, her pupils unequal in size. She asks David to retrieve her mother's ring from Ruth and tells him, "What you do last, that's what counts."
David builds a small fire to create smoke, rigs a tripwire, and arms himself with Susan's broken arm brace. When Ruth, Donny, and Willie rush in, David fights them. Meg rises and steps forward. Ruth seizes Meg's head and smashes it against the concrete wall. Later, Meg wakes one final time, reaches for Susan's hand, and says, "I think I'm going to make it. I think I'll be fine." She dies.
Roughly 90 minutes later, Officer Jennings arrives with David's father and another officer. They open the shelter and confirm Meg is dead. As they file upstairs, David sees Meg's mother's wedding band on Ruth's finger. He pushes Ruth down the staircase, and her neck snaps. Jennings tells the others the boy stumbled. He removes the ring from Ruth's dead hand and gives it to David, who brings it to Susan. They hold each other and cry.
In the epilogue, David recounts the aftermath. None of the children face criminal charges as juveniles. Donny, Willie, and Woofer are sent to juvenile detention until age 18; Eddie and Denise for two years. Susan goes to a foster home. David's parents divorce. He attends college, builds a career on Wall Street, and marries and divorces twice. Years later, sorting through his dead mother's belongings, he finds a newspaper clipping about Woofer's arrest for the murders of two teenage girls in 1978. His mother had written in the margin, "I wonder how Donny and Willie are doing?" On the eve of his third marriage, plagued by nightmares of failing someone, David wonders the same.