The day of their fifth wedding anniversary, writing teacher Nick Dunne returns home to find that his wife Amy is missing. Her disappearance receives heavy press coverage, as Amy was the inspiration for her parents’ popular Amazing Amy children’s books. Detective Rhonda Boney does a walkthrough of their house and finds poorly concealed evidence of a struggle. The police conduct a forensic analysis and uncover the remnants of cleaned blood stains, leading to the conclusion that Amy was murdered. Suspicions arise that Nick is responsible, and his apathetic behavior is interpreted by the media as characteristic of a sociopath.
Flashbacks reveal that Nick and Amy’s marriage had disintegrated; both lost their jobs in the recession and moved from New York City to Nick’s hometown of North Carthage, Missouri. Nick became lazy and distant, and began cheating on Amy with one of his students. Boney unearths evidence of financial troubles and domestic disputes, and a witness states that Amy wanted to purchase a gun. She also finds a medical report indicating that Amy is pregnant, of which Nick denies knowledge, and a diary supposedly written by Amy highlighting her growing isolation, ominously ending with the fear that Nick will kill her.
Amy is revealed to be alive and well, having changed her appearance and gone into hiding in a distant campground in the Ozarks. Upon learning that Nick was cheating on her, she resolved to punish him by framing him for her murder. Amy plans the framing in great detail: she befriends a pregnant neighbor to steal her urine for the pregnancy test, drains her own blood to leave traces of evidence of murder and fabricates a diary describing her fear of Nick. She also has Nick increase her life insurance so it looks like he murdered her for the money. By using the clues in a “treasure hunt” game she and Nick play on their anniversary, she ensures he visits places where she has planted the corroborating evidence of Nick’s guilt for the police to discover. She anticipates Nick will be convicted and executed for her murder, and contemplates committing suicide after his conviction.