On their fifth wedding anniversary, writing teacher Nick Dunne returns home to find his wife Amy missing. Her disappearance receives press coverage, as Amy was the inspiration for her parents’ popular Amazing Amy children’s books. Detective Rhonda Boney finds poorly concealed evidence of a struggle in the house. Suspicion mounts around Nick, whose apathy is interpreted by the media as characteristic of a sociopath and even sows doubt in his twin sister Margo. In the past Amy revealed to Nick that Amazing Amy was a perfected version made up of the real Amy’s failures. Their marriage disintegrated over time; both lost their jobs in the recession and moved from New York City to Nick’s hometown of North Carthage, Missouri, to care for his dying mother. Nick became lazy and distant, and began cheating on Amy with Andie, one of his students, while Amy became increasingly resentful towards Nick for making her move with him to Missouri.
Forensic analysis of the house uncovers cleaned bloodstains, indicating a probable murder. Boney unearths evidence of financial troubles, domestic disputes, and Amy’s recent willingness to purchase a gun. Medical reports indicate that Amy is pregnant, which Nick denies knowing. Amy and Nick had played treasure hunt games on every wedding anniversary; this year’s clues include profligate items purchased with Nick’s credit card, as well as a diary highlighting Amy’s growing isolation and ending with the fear that Nick will kill her. Amy drives to a campground in the Ozarks. Upon discovering Nick’s affair, she had concocted an elaborate plan to frame him for her murder and make his motive appear to be monetary. She fabricated a long-standing diary that was accurate in its early entries but later evolved into false accounts of spousal violence and her increasing fear of Nick. She had befriended a pregnant neighbor, tells her fake stories about Nick’s temper, and steals her urine to fake pregnancy results, all while hiding the friendship from Nick. She plants corroborating evidence of Nick’s guilt in the clue spots for the “treasure hunt” for the police to find. She also splattered her own blood across the kitchen, and cleaned it haphazardly. She anticipated that Nick would be executed for her murder, and planned to kill herself.