Famed mystery writer, Mort Rainey, portrayed by Johnny Depp, finds himself facing a troubling encounter when a stranger appears at his doorstep. This enigmatic figure, John Shooter, played by John Turturro, accuses Mort of stealing his story idea. While Mort insists that he can provide proof of his own work, the situation escalates as Shooter's behavior turns increasingly aggressive.
Initially, Mort perceives Shooter as unstable and dismisses the manuscript thrown out by his housekeeper, only for it to resurface in his thoughts, leading him to read it. To his shock, he discovers that the content closely resembles his own novel, albeit with altered names and phrasing. This revelation sparks a tense battle for Mort, as he struggles to demonstrate to Shooter — and himself — that he has not plagiarized.
As the plot unfolds, Shooter’s harassment intensifies, culminating in the heartbreaking death of Mort's dog, an Australian Cattle Dog named Chico. Mort, desperate for assistance, recruits a private investigator, played by Charles S. Dutton, and seeks help from the local sheriff, Dave Newsome, portrayed by Len Cariou. Unfortunately, the sheriff is skeptical of Mort’s claims. When Mort recollects that a local man witnessed them together, it appears that hope is not lost. Yet, the situation grows dire as Shooter takes matters into his own hands, murdering both the investigator and the witness, leaving their bodies in a car. Fearing that he will be framed for these crimes, Mort decides to dispose of the car by pushing it into a river.
The plot thickens as Shooter retaliates by burning down the house belonging to Mort's soon-to-be ex-wife. Mort believes that his estranged wife’s lover, Ted, is involved in this deceit. In a twist of fate, Mort uncovers the magazine that serves as crucial evidence proving he published "Secret Window" before Shooter's "Sowing Season." However, upon retrieving the magazine, he faces a chilling confrontation with the sheriff, who seems to know more than he lets on.
Further revelations lead Mort to an unsettling conclusion about Shooter — he is not a real person but rather a manifestation of Mort's own psyche, representing the darker parts of himself, a product of undetected dissociative identity disorder. This realization strikes Mort during a pivotal moment in front of a mirror, echoing themes from Magritte's surrealism. Just as Mort's wife arrives at their cabin and begins searching for him, she stumbles upon ominous signs of his split personality. In a tragic turn of events, Mort succumbs to the darker side of himself, leading to the brutal murders of his wife and her lover, Ted, before burying their bodies in a garden where he later plants corn.
As Mort's character transforms, he emerges from a crippling writer's block, rekindling his passion for life — albeit at a horrific cost. The film culminates in a chilling exchange with the sheriff, who ominously hints at the impending discovery of the bodies. Mort dismisses the threat with a calm confidence, declaring, > "The ending is the most important part of the story. This one is very good. This one is perfect." It becomes clear to the audience that the bodies rest beneath the very cornfield that now flourishes.
