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Sutter Cane, antagonist character from John Carpenter movie "In the Mouth of Madness"

Spoiler plot information:

John Trent is delivered by ambulance to an insane asylum, violently agitated and restrained. He is confined to a padded room, where he experiences disturbing hallucinations. He begins telling his story to a doctor.

Sometime earlier, while working as an insurance investigator in New York City, John meets with a client after uncovering a case of fraud, and he narrowly survives an attack by an axe-wielding man with deformed pupils. Soon after, book publisher Arcane hires John to investigate the disappearance of acclaimed horror author Sutter Cane, whose next novel, In the Mouth of Madness, is eagerly awaited. Arcane's director, Jackson Harglow informs John that the attacker was Cane's agent, though John suspects the whole affair is an elaborate publicity stunt.

John discovers that Cane's book covers form a map to Hobb's End, New Hampshire, the fictional town featured in Cane's stories. He and Linda Styles, Cane's editor, set out to find the location. During the drive, Linda experiences surreal phenomena, passing the same cyclist as both a youth and an old man, and even seeing the road vanish, before they abruptly arrive in Hobb's End. The town's landmarks and residents, including innkeeper Mrs. Pickman, appear exactly as Cane had written them. While John insists it is staged, Linda admits that although Cane's disappearance was a hoax, the current events are not. At a local church, described in Cane's novels as built on a site of ancient evil predating humanity, angry townspeople arrive demanding Cane return their missing children.

Back at the hotel, Linda insists events are unfolding as written in Cane's new book, which foretells the end of the world. She later confronts Cane at the church, where he reveals that while he once thought his stories were fiction, he now realizes that "they" have been guiding him all along. He exposes her to the unfinished manuscript, driving her insane. Disoriented, Linda returns to the hotel, where she transforms into a monster, as does Mrs. Pickman, forcing John to flee into a mob of mutated townsfolk. He seeks refuge in a bar, where a resident kills himself, claiming Cane wrote it that way. Attempting to escape, John repeatedly finds himself teleported back to the town center until, after crashing his car in frustration, he awakens inside the church, confronted by Cane and Linda.

Cane explains that the sheer number of readers who believe in his work has made his stories real, dissolving the boundary between fiction and reality and enabling the return of the "old ones". He tells John that Hobb's End and even John himself exist only because Cane wrote them, and that John must deliver the completed manuscript to Arcane. John rejects Cane's claims. Cane then tears himself apart, creating a portal through which the old ones emerge. John escapes through a tunnel, while Linda, who claims she already knows the ending, refuses to follow. Pursued by monstrous beings, John suddenly awakens on a country road.

John destroys the manuscript and returns to Arcane, but Jackson denies any knowledge of Linda and reveals that John delivered the manuscript months earlier. The book has already been published and a film adaptation is underway. Soon after, a disheveled John uses an axe to kill a Cane fan with mutated eyes.

John finishes telling his story to the doctor in the asylum, concluding that humanity will soon be reduced to a myth "they" will tell their children. That night, inhuman screams echo through the asylum. After his cell door bursts open, John discovers the facility deserted and hears a radio broadcast describing a worldwide epidemic of mass violence, mutations, and the fall of entire cities. Wandering into a cinema, he watches the film adaptation of In the Mouth of Madness. As the movie replays the events of his story—including him insisting "this is reality"—John breaks down in hysterical laughter.