[[quoteright:280:http://static.tvtropes.org/pmwiki/pub/images/Mouthmadnessposter.jpg]]
[[caption-width-right:280:Ever lost yourself in a good book?]]

->''A reality is just what we tell each other it is.''

->''Do you read Sutter Cane?''

The third installment of Creator/JohnCarpenter's [[ThematicSeries "Apocalypse Trilogy"]] (preceded by ''[[Film/TheThing1982 The Thing]]'' and ''Film/PrinceOfDarkness''), '''''In the Mouth of Madness''''' explores reality, fiction, and the thin, horrific line that separates the two.

John Trent (SamNeill), insurance fraud investigator, has just been placed in an insane asylum. Months earlier, he was hired to find bestselling horror writer Sutter Cane (Jürgen Prochnow). Cane has disappeared under mysterious circumstances, but his publishers think it might just be a stunt to drum up support for his next book, ''In the Mouth of Madness''.

When Trent finds that the covers of Cane's books seem to become a map to the supposedly fictional town of Hobb's End, he and Linda Styles (Julie Carmen), who works for the publisher, decide to go there and find Cane. What they find, however, is something much worse.

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!!This film gives examples of:

* AnythingButThat: "Oh, no. Not The Carpenters, too."
* ApocalypseHow: Though it's left deliberately vague precisely what's happening, precisely how bad it is, and precisely how real it is.
* ArcWords: "Do you read Sutter Cane?"
* AuthorAvatar: Literally: Cane might just be an avatar of whatever extra-reality force he has become/is channeling.
* AuthorPowers: Cane's powers have become so vast that the entire world is his story.
* AxeCrazy: [[AnAxeToGrind Literally]]. Some characters just pick up an axe and start swinging after reading Cane's book.
* BedlamHouse: At the start of the film, we find Trent locked up in a mental asylum, [[InMediasRes from which he tells the rest of the story prior to his arrival there to a psychiatrist]].
* BiggerThanJesus: Sutter Cane says more people believe in his novels than believe in the ''Literature/TheBible''.
* {{Bizarrchitecture}}: The church. On the outside it's spooky enough, what with its rural New England location, but inside it turns into a full blown EldritchLocation.
* BodyHorror: Going nuts is one thing, but it's possible that Cane's book can even turn people into EldritchAbomination.
* BreakingTheFourthWall: [[spoiler:"Did I ever tell you my favorite color is blue?" Every character's eyes are blue in closeup, whether or not the actor or actress actually has blue eyes.]]
* BrownNote: The whole premise. Cane's book clearly does terrible things to readers and, perhaps, the entire world.
* CatapultNightmare: Trent startles awake from his alleyway nightmare. In fact, the movie features nesting Catapult Nightmares.
* ClingyMacGuffin: Once Trent has the manuscript, he can't get rid of it. Even when he destroys it, it reappears very quickly.
* {{Confessional}}: Insane author Sutter Cane discusses the power of faith over reality with the protagonist while they sit on opposite sides of a confessional.
* CosmicRetcon: Essentially the entire movie.
** [[spoiler: Linda Styles may never even have existed. Trent may only have begun existing when Cane wrote him. Hobb's End seems to become real/unreal purely through Cane's words.]]
** Finally, it's even possible that [[spoiler:of the movie ([[TheFourthWallWillNotProtectYou the ''movie itself'' may have been written/created by Sutter Cane.]]]]
* CreditsGag: Right after the "No animal was harmed during the making of this film" blurb, they have a slightly different report on the humans.
* CreepyBasement: Mrs. Pickman's basement.
* CreepyChangingPainting: The picture in Mrs. Pickman's foyer.
* CreepyChild: The children of Hobb's End are slowly turning into homicidal monsters and mutilate a dog.
* DeadpanSnarker: Trent, at least before the façade starts to slip.
* TheDeterminator: Trent doesn't really give a crap if Cane is God. He's still going to tell him, "Up yours."
* DownerEnding: [[spoiler:The film ends with the apocalypse, as the entire world is attacked by [[EldritchAbomination Lovecraftian horrors]] and a large chunk of the population falls into insanity. Of course, if reality is relative anyway, then does this ending even matter/happen?]]
* DramaticThunder: Thunder can be heard during Trent's stay in the mental asylum.
* DreamWithinADream: See CatapultNightmare.
* DrivenToMadness: Probably Trent. Likely Cane. Maybe the whole world? Or it could be none of these people are real anyway...
* DrivenToSuicide:
-->"I have to, he [Sutter Cane] wrote me this way."
* EldritchAbomination: The Old Ones. When they enter reality through Sutter Cane's book, they herald the end of humankind.
* EldritchLocation: Hobb's End, but especially the interior of the church.
* EndlessCorridor: The passage way that leads back from Hobb's End to the real world.
* FictionalDocument: All of Cane's books, most notably ''In the Mouth of Madness''.
* FilmNoir
* TheFilmOfTheBook: In-universe, Cane's publishing company sold the movie rights to Cane's latest novel. [[spoiler:Trent watches it in a theater at the very end, and it turns out to be...the very movie we're just finished watching.]]
* {{Fingore}}: In a NightmareSequence, a character gets his fingers cut off.
* TheFourthWallWillNotProtectYou: It is not a coincidence that the title of this film is also the title of Cane's insidious book ''and of its film adaptation.''
* GenreSavvy: Having read Cane's books, the characters know what to expect. Whether they choose to believe that the books correspond to reality is another matter.
* AGodAmI: ZigZagged with Sutter Cane. In this case, he may very well be, as his writings have granted him the ability to recast the entirety of reality through his novels. On the other hand, it's made clear that he is actually in service to a host of Lovecraftion terrors that are slowly invading the world.
* GoMadFromTheRevelation: [[spoiler:Trent, finally realizing that he was a Sutter Cane character all along. Presumably everyone else driven mad by the book/movie had this same revelation.]]
* GoingInCircles: Trent tries to drive out of town repeatedly but ends up right where he he started.
* GroinAttack: When he's being taken in at the mental asylum, Trent attacks one of the orderlies this way.
* GroundhogDayLoop: When Hobb's End really goes to hell and people start mutating into monsters all around Trent, he decides to get the hell out of dodge and jumps in his car. Each time he tries to leave town, however, the godlike Cane resets Trent to just before he left. The only option left to him is go right through the ax-wielding mob of townspeople.
* HellHotel: Mrs. Pickman's hotel.
* HowWeGotHere: Almost the entire story is told InMediasRes by John Trent to a psychiatrist at a mental asylum.
* IAmAHumanitarian: In Trent's nightmare, one of the monster people eats part of a person they just axed to death.
* IDontLikeTheSoundOfThatPlace: Hobb is an old English word for Devil.
* InMediasRes: The film begins with Trent's commitment, as he relays HowWeGotHere to Wren.
* InsuranceFraud: A guy burns down his warehouse of [[PrettyInMink fur coats]], but it turns out just stashed them away, and gave one to his wife... and another to [[TheMistress his mistress]]. Catching both those ladies in their coats gave the guy away.
* InvincibleVillain: Cane is basically God, at least as far as the other characters are concerned.
* JumpScare: Used extensively.
* KickTheDog: Quite literally. Our introduction to the [[CreepyChild terrifying children]] of Hobb's End shows them running after a dog. The next time we see them, the dog has had one of its legs ripped off and is limping around forlornly.
* KillItWithFire: Doesn't work.
* LaughingMad: Trent.
* LeaningOnTheFourthWall: When Dr Wren asks what will happen to those who don't read (and therefore won't read Cane's book), Trent answers : "There's [[Film/InTheMouthOfMadness a movie]]!". [[spoiler:He's not kidding, and [[MindScrew that link is extremely appropriate;]] the movie happens to be ''the one you're watching.'']]
* LovecraftCountry: Hobb's End. The film is inspired by, and contains ShoutOut after ShoutOut to Lovecraft. Hell, a nightmare sequence even has a ContinuityCameo from Cthulhu.
* MaybeMagicMaybeMundane: Have Sutter Cane's books triggered a mass delusion that's causing more and more people to think they're being taken over by monstrous demons? Or are monstrous demons really taking over people who have read Sutter Cane?
* MindScrew: What's the difference between fiction and reality? According to this movie, nothing, up to and including ''the movie itself''.
* TheMistress: An InsuranceFraud scam is found out when a guy claims a warehouse full of [[PrettyInMink fur coats]] was supposedly destroyed, but he kept the coats, giving some to his wife, who ratted on him when it turned out he gave some to his mistress.
* MonochromaticEyes: Cane's eyes during the mock-confessional.
* MostWritersAreWriters: Sutter Cane is the most popular (horror) writer who ever lived and he's ''the villain'' no less. At its core the film looks at what the awesome power of writing [[RewritingReality means to the characters who occupy the novels themselves]].
* NameOfCain:
* NightmareDreams: Trent has an extensive one that takes place in an alleyway at night.
* NoCelebritiesWereHarmed: Sutter Cane is an obvious stand-in for Stephen King. Less directly, he also represents director John Carpenter. Since both men were widely influenced by HP Lovecraft, Cane's works seem to strongly resemble Lovecraft's own.
* NoFourthWall: An ''in universe'' example that breaks through two fourth walls. [[spoiler:At the end, Trent views the film you are watching, only disjointed and cut up.]]
* NothingIsScarier: Cane's ultimate reveal is just a black void.
* NoticingTheFourthWall: [[spoiler:At the end of his stay in Hobb's End, Trent meets with Sutter Cane. Cane reveals that Trent is in fact one of his characters. Trent refuses to accept this, exactly how Cane had written him.]]
* OnlySaneMan: Trent insists that he knows what reality is, and to hell with what anyone else says. [[spoiler: He gives up the pretense at the end. Although he really ''is'' the only sane man, because [[FridgeBrilliance that's how Cane wrote him]].]] {{Discussed}} by Cane: "Always looking for the con... even now you're trying to rationalize."
* {{Phlegmings}}: Demonstrated by the Old Ones when they pursue Trent into the portal.
* ThePlague / TheVirus: People beginning their slide into madness show plague-like symptoms of open sores and wonky eyes.
* PoliceBrutality: As Trent walks through an alleyway at night, he catches a cop beating up a homeless man. He leaves it alone, but the cop is ready to dish out some more. He later sees a nightmare of the same scene.
* {{Postmodernism}}
* PrettyInMink: A guy burned down a warehouse of fur coats [[InsuranceFraud to collect the insurance]]. He was caught when it turned out he kept the coats safe, and gave some to his wife, and [[TheMistress his mistress]].
* RealityWarper: Sutter Cane becomes so powerful that he can alter reality to suit his whims. According to WordOfGod, [[spoiler: Cane has no more power than any other writer. The entire film is taking place inside one of his books.]]
* RecurringDreams: Trent begins to suffer from these. [[spoiler: Turned out Cane was just writing a little {{Foreshadowing}} into proceedings.]]
* RedRightHand: Readers of the books of hack horror writer Sutter Cane go insane and develop strange physical afflictions, like a second pupil in their iris, or bleeding from their eyes. And berserk homicidal tendencies, of course. Over the time, these minor affliction develop into serious bodily mutations- including tentacles, distended jaws, and reversible joints.
* RetGone: [[spoiler:Linda Styles]].
* RewritingReality: Hobb's End was written into existence by Sutter Cane, who also produces a number of retcons that remove a character from existence and reshuffle an entire sequence of events within the film. By the end of the film, the entire world has apparently been absorbed by Cane's latest novel.
* RoomFullOfCrazy: Notably, Trent starts out the movie having made his own filled with [[CreepyCoolCrosses drawn crosses]] with just a single black crayon. It's even [[LampshadeHanging lampshaded]] by Dr. Wren who thinks that Trent isn't as mad as people think.
-->"The crosses are a nice touch. They'd almost have to keep you in here after seeing these, wouldn't they?"
* RuleOfScary: Hobb's End runs on this.
* ShoutOut:
** Lots to Creator/HPLovecraft. Mrs. Pickman's name is a reference to the story "Pickman's Model," and the titles of Cane's books resemble those of Lovecraft stories. The movie's own title is vaguely reminiscent of ''At the Mountains of Madness.''
** Sutter Cane is basically a [[NoCelebritiesWereHarmed fictional version]] of Creator/StephenKing. ''Literature/{{Cujo}}'' also makes a cameo.
** Hobb's End is also a reference to the ''Franchise/{{Quatermass}}'' films.
** Sapirstein is the name of the Satanist doctor in RosemarysBaby.
* SpookyPainting: Mrs. Pickman's hotel lounge is adorned by a painting of a couple standing besides a lake. Every time Trent takes a look at it again, the couple transform more and more into shrieking human-tree hybrids.
* StepfordSmiler: Mr. Saperstein.
* SurrealHorror
* TearsOfBlood: On those who read Cane's latest book.
* ThisIsReality: Trent insists on this and states it word for word.
-->"This is reality!" *[[{{Foreshadowing}} knocks on wood]]*
* ThroughTheEyesOfMadness: In this movie you're not just in the mouth of madness, you're being ''chewed.''
* TitleDrop: The movie title is that of Sutter Cane's latest novel. It's title dropped by Sutter Cane when he finishes the novel's manuscript for Trent to return it to the real world.
-->"All done. ''In the Mouth of Madness''."
** Also earlier by a newscaster:
-->"Police believe the riots began because the stores could not meet the demand for advance orders of Sutter Cane's latest novel, ''In the Mouth of Madness''."
* TorchesAndPitchforks: Wielded by the corrupted inhabitants of Hobb's End as Trent is trying to leave with Styles.
* TouchedByVorlons: Or EldritchAbomination, in this case.
* TownWithADarkSecret: Hobb's End, of course.
* TreasureMap: Trent "discovers" the secret location of (the supposedly fictional) Hobb's End by piecing together a jigsaw map made from secret shapes hidden in the cover art of Cane's novels.
* UnreliableNarrator: Is the entire world the product of an Unreliable Narrator?
* UnnaturallyBlueLighting: See BreakingTheFourthWall.
* WindowPain:
** Used when When cane visits Trent in the mental asylum.
** Cane's agent bursts into the restaurant Trent is having dinner with an employer by breaking the plate glass window with an axe.
* YouHaveToBelieveMe: First, Linda Styles tries this, only for Trent to not believe her. Eventually Trent himself gets plenty of moments like this, particularly near the end.

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