It’s Nick and Amy Dunne’s fifth wedding anniversary, and Nick Dunne wakes up in a cold sweat in Carthage, Missouri. He creeps downstairs, avoiding his wife, and heads to the bar he owns with his twin sister, Go. Nick, Amy, and Go moved back to Missouri about two years previously, after the Great Recession of 2008. All three were laid off from their comparatively high-powered New York jobs, and Nick’s dying mother needed money and care. Amy—a lifelong Manhattanite and the only daughter of the successful writers of the Amazing Amy novel franchise—agrees to move because her parents lost all their money and had to borrow $650,000 from her trust fund. She and Nick have been arguing constantly since he lost his job, and in Amy’s mind the move to Missouri is supposed to fix things. They’re clearly individually and collectively miserable, but they are maintaining a public veneer of civility. However, on that same anniversary morning in 2012, after discovering his cat has escaped and his front door is swinging open, Nick finds his house in disarray and Amy missing. 

The narrative jumps between Nick’s present-day troubles and Amy’s diary from the early 2000s, telling both sides of a love story that seems very one-sided at first. Amy writes about the giddy start of their relationship in 2005, swooning over Nick. In 2012, Nick sits in his Missouri kitchen being interrogated by Detectives Boney and Gilpin because they suspect he might have murdered her. Nick is sweating and terrified, because he knows that in almost every case of a wife’s disappearance, the husband is the guilty party. He doesn’t seem to know what has happened to Amy at this point. What he does know, and immediately tells the police, is that his wife will have left him her usual anniversary “surprise.” Every year, Amy makes an increasingly passive-aggressive treasure hunt around the city for Nick to follow. As Nick tries to decode Amy's clues, which are all sneakily designed to show him the ways he’s failed her as a husband, the police discover more and more evidence that implicates Nick in Amy’s disappearance. While this is happening, Nick also regularly silences or doesn’t answer calls on a burner cellphone.  

When the case hits the press, the media leaps on the opportunity to vilify Nick, as he’s compellingly handsome and seems very insincere on camera. Amy’s parents come to town and help in the search effort. At first, they’re very supportive of Nick, but as evidence starts to suggest he’s harmed Amy, they and the public begin to withdraw from him. The police find huge amounts of unpaid credit card debt in Nick’s accounts, a staged-looking crime scene, and badly cleaned traces of blood in Nick and Amy’s kitchen. Evidence also crops up that attests Amy attempted to purchase a gun at the abandoned mall in Carthage because she didn’t feel safe. When Nick finally reveals who’s been calling him, it implicates him even further: the calls are coming from his 23-year-old mistress Andie, whom he’s been cheating on Amy with for two years. 

Meanwhile, Amy’s diary entries detail a marriage in rapid decline, starting with the beginnings of doubt and ramping up to full-fledged accusations of mental and physical abuse. As they are interspersed with Nick’s involvement in the search efforts, it seems overwhelmingly likely to the reader that Nick is responsible for her disappearance. Their neighbor Noelle comes forward to reveal that Amy was pregnant, and that Amy told her that Nick was abusive. Nick, who’s growing desperate as everyone from talk show hosts to his parents-in-law declare him guilty, hires the famous “savior of wife-killers,” defense lawyer Tanner Bolt. As he flies back from Tanner’s office in New York, Nick figures out the answer to Amy’s last clue: he’s supposed to go to the woodshed on Go’s property. Amy’s last diary entry states that she’s afraid Nick will kill her. 

There’s a shocking twist at this point. The narrative switches to Amy’s present-day perspective. She has deliberately framed Nick for her murder. She knew about Nick’s infidelity, and after a lifetime of being used by her parents as inspiration for their books and years of being treated badly by Nick, she’s had enough. Narrating from the first stop in a multi-stage coup, Amy explains how she faked her death to punish Nick for being a bad husband. She meticulously set up false evidence of abuse and pregnancy, including fabricating all of the previous diary entries. She’s planning to commit suicide to ensure Nick's conviction for her murder, as soon as she’s sure he’ll get the death penalty. 

Nick tries to keep his cool, but he discovers that Amy has filled the woodshed with all the expensive purchases she made in order to create a trail of debt and reckless spending for the police to find. Andie comes forward and apologizes for her affair with Nick, but he’s able to turn this near-disaster around when Tanner gets him an appearance on Sharon Scheiber’s tell-all talk show. However, Nick is arrested when the police discover the “murder” weapon: it’s the bloodied handle of the Judy puppet from a set of Punch and Judy toys Amy left for Nick in the woodshed.  

Amy hides in the Ozarks and attempts to watch Nick’s trial-by-public-opinion progress from the safety of her cabin. However, Jeff and Greta, her neighbors at the rental cabin spot, promptly steal her money. Amy panics, but then calls Desi Collings, a former boyfriend of hers who has always been obsessed with her. Desi swoops in to “save” her, imprisoning her in his luxurious lake house and threatening to call the cops if she leaves.  

At the same time as this upheaval, Nick gives a compelling and sincere interview saying how sorry he is for everything and how much he loves Amy, which she and Desi watch together. Amy decides it’s time to go back to Nick, as the interview has proven to her that he can be the man she wants. She frames Desi for her kidnapping, making it look as though he raped and restrained her, and kills him. She drives back to Carthage and runs into Nick’s arms in front of the press. 

Amy manipulates her return to fit her narrative. Despite the police's suspicions and Nick’s protestations that he’s been framed, Amy's detailed planning leaves little room for doubt that her story is true. She still worries that Nick will leave her, so she uses sperm he stored years ago to get herself pregnant. Nick and Amy each write a memoir about the experience. Amy’s is called Amazing, after her parents’ fictional version of her, and Nick’s is called Psycho Bitch, also after her. Nick, although he’s aware of the full extent of Amy's manipulations, is trapped into staying with her because he refuses to abandon his child. Despite his desire to expose Amy's horrible behavior, he chooses fatherhood over freedom, destroying his manuscript. Amy, triumphant over her “win” but still nursing doubts about Nick’s plans, claims the “last word” of the novel.