After catching his wife Amy having an affair with their friend Ted, mystery writer Mort Rainey retreats to his cabin at Tashmore Lake in upstate New York, while Amy stays in their marital home. Six months later, Mort, depressed and suffering from writer's block, has delayed finalizing the divorce.

One day, a man named John Shooter arrives at the cabin and accuses Mort of plagiarizing his short story, "Sowing Season". Upon reading Shooter's manuscript, Mort discovers it is virtually identical to his own story, "Secret Window", except for the ending. The following day, Mort, who once plagiarized another author's story, tells Shooter that his story was published in a mystery magazine two years before Shooter's, invalidating his plagiarism claim. Shooter demands proof and warns Mort against contacting the police. That night, Mort's dog, Chico, is found dead outside the cabin, along with a note from Shooter giving Mort three days to provide proof.

Mort reports the incident to Sheriff Newsome. Mort drives to his and Amy's house intending to retrieve a copy of the magazine, but he leaves because Ted and Amy are there. Mort instead hires private investigator Ken Karsch, who stakes out the cabin and speaks to Tom Greenleaf, a local resident who thinks he saw Shooter and Mort talking together. At the cabin, Shooter appears and demands that Mort revise the ending of his story, giving it Shooter's twist, in which the protagonist kills his wife. When an arson fire destroys Amy and Mort's house, and presumably the magazine, Mort reveals to the police that he has an enemy.

Karsch tells Mort that he suspects someone has threatened Greenleaf after Greenleaf suddenly claims he never saw Mort and Shooter talking together. Mort and Karsch agree to confront Shooter but first plan to meet up with Greenleaf at the local diner the next morning. Arriving late, Mort discovers that neither Karsch nor Greenleaf showed up at the diner. On his way home, Mort encounters Ted at a gas station, where Ted demands that Mort sign the divorce papers. Believing Shooter is in Ted's employ, Mort refuses, taunts Ted, and leaves.

Later, Shooter summons Mort to a meeting place; when he arrives, Mort finds Karsch and Greenleaf dead inside Greenleaf's truck and passes out at the sight. When he recovers Shooter tells Mort he killed the two men because they had "interfered" in his business. He warns Mort that he has deliberately implicated him in the two men's murders (having used Mort's axe and screwdriver as the murder weapons) and implies Mort should dispose of the bodies. Mort agrees to meet Shooter at his cabin to show him the magazine containing his story, which is supposed to arrive that day, having been sent overnight by his literary agent. Mort later retrieves his tools and then pushes Greenleaf's truck with both bodies still in it off a steep cliff into a water-filled quarry, where it sinks.

Mort retrieves the package containing the magazine from the post office but finds that it has already been opened; the pages containing his story have been cut out. At Mort's cabin, Mort sees Shooter's hat, puts it on, and begins speaking to himself, trying to make sense of the events. Frustrated and in denial, Mort throws an object at the wall and is surprised to see a growing crack fracture the cabin in half. Looking in the mirror, he's startled to see the back of his head reflected instead. Mort realizes that Shooter is a figment of his imagination, a character brought to life through Mort's undetected dissociative identity disorder, unwittingly created to cope with his anger and carry out malevolent tasks that Mort cannot do – like killing Chico, Greenleaf, and Karsch, as well as burning down Amy's home. That persona now takes full control of Mort.

Amy arrives at the cabin, finding it ransacked, and she sees the word "SHOOTER" carved repeatedly on the walls and furniture. Mort appears, wearing Shooter's hat and speaking and acting like him. Amy realizes the name "Shooter" represents Mort's desire to "SHOOT HER". He chases Amy and stabs her in the leg. Ted, looking for Amy, arrives and is ambushed by Mort, who kills him with a shovel. Amy watches helplessly as Mort bludgeons Ted and then approaches her while reciting the ending of "Sowing Season".

Months later, Mort has recovered from his writer's block, and his passion for life has returned. He is feared and shunned in town because of the rumors about the missing people associated with him. Sheriff Newsome arrives and tells Mort that he is the prime suspect in the supposed murders and that the bodies will eventually be found. Newsome then says that Mort is no longer welcome in town. Mort passively dismisses the threat and tells Newsome that the ending to his new story is "perfect". It is implied that Amy and Ted's bodies are buried under the corn growing in Mort's garden, allowing Mort to gradually eliminate any evidence of their murders. (In an alternative ending available on home media, their bodies are shown under the earth.)

• Johnny Depp as Morton "Mort" Rainey
• John Turturro as John Shooter
• Maria Bello as Amy Rainey
• Timothy Hutton as Ted "Teddy" Milner
• Len Cariou as Sheriff Dave Newsome
• Charles S. Dutton as Private Investigator Ken Karsch
• John Dunn Hill as Tom Greenleaf

Part of Secret Window was filmed in the town of North Hatley, Quebec in the Eastern Townships approximately two hours south east of Montreal.^[2][3] Other filming locations included Lake Massawippi, Lake Sacacomie, Lake Gale and the village of Bromont, Quebec.^[4]

According to director David Koepp on the DVD commentary track, the footage of the ocean scene during Mort's restless night on the couch was extra b-roll footage taken from The Lost World: Jurassic Park.^[5]

The film's ending is different from the source novella. In the novella, Ted and Amy survive Mort's attempt on their lives, and Mort dies. It is also revealed that through supernatural forces, the fictional John Shooter had manifested and come to life from Mort's imagination, and really was the one to commit the murders and arson.

Roger Ebert awarded Secret Window three stars out of a possible four, stating that it "could add up to a straight-faced thriller about things that go boo in the night, but Johnny Depp and director David Koepp ... have too much style to let that happen." He continues by noting that the "story is more entertaining as it rolls along than it is when it gets to the finish line. But at least King uses his imagination right up to the end, and spares us the obligatory violent showdown that a lesser storyteller would have settled for."^[6] Ian Nathan from Empire only awarded the film 2 stars out of a possible 5, stating that "The presence of the sublime Depp will be enough to get Secret Window noticed, but even his latest set of rattling eccentricities is not enough to energise this deadbeat parlour trick."^[7]

On Rotten Tomatoes, Secret Window has an approval rating of 46% based on 163 reviews, with an average rating of 5.50/10. The site's critics' consensus reads: "Depp is quirkily entertaining, but the movie runs out of steam by the end."^[8] On Metacritic, the film has an aggregated score of 46 out of 100 based on 34 critics, indicating "Mixed or average reviews".^[9] Audiences polled by CinemaScore gave the film an average grade of "C+" on an A+ to F scale.^[10]

The film was a modest box office success, succeeding at recouping its budget of $40 million with a worldwide gross of $92.9 million.

An alternate ending was included on the home media release, explicitly showing both Ted's and Amy's dead bodies underneath the corn patch in Mort's garden. In the theatrical release, this is implied, but the bodies are not shown.

• List of films featuring mental illness

• Secret Window at IMDb  
• Secret Window at AllMovie  
• Secret Window at Box Office Mojo  
• Secret Window at Rotten Tomatoes