The third installment of John Carpenter's "Apocalypse Trilogy" (preceded by The Thing and Prince of Darkness), In the Mouth of Madness explores reality, fiction, and the thin, horrific line that separates the two.John Trent (Sam Neill), 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.
The Determinator: Trent doesn't really give a crap if Cane is God. He's still going to tell him, "Up yours."
Downer Ending: The film ends with the apocalypse, as the entire world is attacked by 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?
Dramatic Thunder: Thunder can be heard during Trent's stay in the mental asylum.
The Film of the Book: In-universe, Cane's publishing company sold the movie rights to Cane's latest novel. Trent watches it in a theater at the very end, and it turns out to be...the very movie we're just finished watching.
Genre Savvy: 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.
A God Am I: Zig-Zagged 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.
Go Mad from the Revelation: 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.
Going in Circles: Trent tries to drive out of town repeatedly but ends up right where he he started.
Groin Attack: When he's being taken in at the mental asylum, Trent attacks one of the orderlies this way.
"Groundhog Day" Loop: 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.
Insurance Fraud: A guy burns down his warehouse of fur coats, but it turns out just stashed them away, and gave one to his wife... and another to his mistress. Catching both those ladies in their coats gave the guy away.
Invincible Villain: Cane is basically God, at least as far as the other characters are concerned.
Kick the Dog: Quite literally. Our introduction to the 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.
Maybe Magic, Maybe Mundane: 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?
Mind Screw: What's the difference between fiction and reality? According to this movie, nothing, up to and including the movie itself.
The Mistress: An Insurance Fraud scam is found out when a guy claims a warehouse full of 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.
Nightmare Dreams: Trent has an extensive one that takes place in an alleyway at night.
No Celebrities Were Harmed: 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.
No Fourth Wall: An in universe example that breaks through two fourth walls. At the end, Trent views the film you are watching, only disjointed and cut up.
Noticing The Fourth Wall: 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.
Only Sane Man: Trent insists that he knows what reality is, and to hell with what anyone else says. He gives up the pretense at the end. Although he really is the only sane man, because 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.
The Plague / The Virus: People beginning their slide into madness show plague-like symptoms of open sores and wonky eyes.
Police Brutality: 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.
Reality Warper: Sutter Cane becomes so powerful that he can alter reality to suit his whims. According to Word of God, Cane has no more power than any other writer. The entire film is taking place inside one of his books.
Red Right Hand: 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.
Rewriting Reality: 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.
Room Full of Crazy: Notably, Trent starts out the movie having made his own filled with drawn crosses with just a single black crayon. It's even 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?"
Lots to H.P. Lovecraft. 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.
Spooky Painting: 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.