[[quoteright:280:http://static.tvtropes.org/pmwiki/pub/images/Mouthmadnessposter.jpg]]
[[caption-width-right:280:Getting lost in a good book takes on a twisted meaning here.]]

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

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

The third installment of 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: [[spoiler:Humanity is in full-on societal breakdown, and may very well go extinct. It's left deliberately vague as to whether people are just losing their minds, or are being invaded by a species of {{Eldritch Abomination}}s.]]
* ArcWords: "Do you read Sutter Cane?"
* AxeCrazy: [[AnAxeToGrind Literally]], Sutter's agent in the beginning. [[spoiler: Later on, literally ''everyone''.]]
* 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 repeatedly claims more people believe in his novels than believe in the ''Literature/{{Bible}}''.
* {{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: Mrs. Pickman and [[spoiler:Linda Styles]]. [[spoiler:Sutter Cane also gets an EldritchAbomination head ''on the back of his own''!]]
* BreakingTheFourthWall: [[spoiler:"Did I ever tell you my favorite color is blue?"]]
** FridgeBrilliance: [[spoiler:Every character's eyes are blue in closeup, whether or not the actor or actress actually has blue eyes.]]
* BrownNote: The whole premise.
* CatapultNightmare: Trent startles awake from his alleyway nightmare, [[spoiler:but it turns out that he's still asleep when he finds the monstrous cop sitting next to him on his living room couch. He has a second Catapult Nightmare when he wakes up for real.]]
* ClingyMacGuffin: Once Trent has the manuscript, he can't get rid of it. Even when he destroys it, it reappears very quickly.
** To make matters worse, when Trent tries to explain to the publisher what happened and prevent the book from being published [[spoiler: he finds out he already delivered it, the book's been published and is selling like hotcakes, and there's a movie due to come out in a month]].
* 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. When Trent enters she has half mutated into some sort of monster, and kills her husband with an axe.
* CreepyChangingPainting: The picture in Mrs. Pickman's foyer.
* CreepyChild: The children of Hobb's End.
* DeadpanSnarker: Trent, at least before the façade starts to slip.
* 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 [[spoiler:Very likely Trent at the end.]]
* DrivenToSuicide: One of the town's residents kills himself with a shotgun in front of Trent after his daughter attacked him and his wife. He makes it clear that he doesn't have a choice in the matter, as he knows that this is what he was created for in the first place.
-->"I have to, he [Suttter 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 for starters, 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.]]
* {{Fingore}}: In a NightmareSequence, a character gets his fingers cut off.
* 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:During the ending, after witnessing the collapse of human civilization in a rising tide of madness and mutation, John Trent cracks when he discovers that the nightmarish book that did the deed was just a novelisation of everything he did in the last few days. He finds this out by watching the film adaptation. More to the point, it's rather implied that Trent's burst of laughing madness is due to his realization that he is in fact a fictional character, perhaps even of not only Sutter Cane, but also the screenwriter of this movie.]]
* 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.
* 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.
* 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. [[spoiler: Since at that point, burning the book is like trying to burn the entire world.]]
* LaughingMad: [[spoiler:Trent at the very end]].
* 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]]!".
* 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? Characters who haven't read his latest book think the former, those who have read it think the latter, and at one point Linda says it won't really matter either way once the believers outnumber the skeptics.
* MindScrew: What's the difference between fiction and reality? According to this movie, nothing, up to and including ''the movie itself''.
* MonochromaticEyes: Cane's eyes during the mock-confessional.
* NameOfCain: Sutter ''Cane''.
* NightmareDreams: Trent has an extensive one that takes place in an alleyway at night.
* NoCelebritiesWereHarmed: Sutter Cane is a mixture of Creator/StephenKing and Creator/HPLovecraft.
* 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: [[spoiler: The Old Ones' arrival is heralded by a yawning void... of blackness.]] Linda reads out what the protagonist is seeing.
* OnlySaneMan: John's insistence through almost the entire film. [[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 [[EvilEye wonky eyes]]. [[spoiler: At first it turns out Cane is behind it all, but then it's revealed that the Old Ones were directing everything Cane has done.]]
* 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.
* 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.
** 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: The eventual fate of [[spoiler:Linda Styles]].
* RewritingReality: Hobb's End and [[spoiler:John Trent]] were written into existence by an author called 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. It should be noted that once he finishes his novel close to the end of the film, Cane appears to be able to warp reality at will, as demonstrated with the conversations he has with John Trent.
* 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: A rare in-universe example; Hobb's End runs on this [[spoiler: because it's the product of Sutter Cane's imagination.]]
* ShoutOut:
** Lots to Creator/HPLovecraft, including several names, like Mrs. Pickman. And the title is reminiscent of both Lovecraft's novella ''At the Mountains of Madness'', and the town of Innsmouth, mentioned in several of his stories.
** Sutter Cane is basically a [[NoCelebritiesWereHarmed fictional version]] of Creator/StephenKing.
*** ''{{Cujo}}'' 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: [[spoiler:The movie was heavily inspired by the Cosmic Horror of Creator/HPLovecraft. To make it even better, the question isn't just limited to whether John Trent is (in)sane or not, but also whether he actually exists or is just a figment of the in-story horror writer's imagination (or for that matter, a figment of the screenwriter's mind). The man's not just in the mouth of madness, but ''being digested''.]]
* 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''."
* TomatoInTheMirror: [[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.]]
* 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: The secret being that [[spoiler: ''the town only exists in Sutter Cane's mind.'']]
* 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: What's real and what's all in Trent's head? Is the entire world the product of an Unreliable Narrator?
* UnnaturallyBlueLighting: See BreakingTheFourthWall.
* WindowPain:
** Used when [[spoiler:Cane]] visits Trent while he's locked up 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.

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