Sutter Cane (Jurgen Prochnow) is an author who combines the cosmic terror of H.P. Lovecraft with the commercial appeal of Stephen King. Writing about slimy monsters from beyond the known universe, Cane is the century's most widely read author. But his work affects his less stable readers, leading to an epidemic of paranoid schizophrenia. For his new novel, In the Mouth of Madness, his fans are literally rioting in the street.
But Cane has disappeared before delivering his manuscript. His publisher (Charlton Heston) wants the book because it's a huge cash cow, so he brings in John Trent (Sam Neil). Trent, a freelance insurance investigator who specializes in debunking fraudulent claims, suspects a scam. But his investigation leads him to Hobb's End, a town in New Hampshire that only exists in Cane's writing. That's where the line between fantasy and reality blurs, which spells bad news for Trent and the human race.
Although not based on any specific story of Lovecraft, John Carpenter's In the Mouth of Madness (1994) has the hallmark of many of his stories. It begins in an insane asylum, with a crazed Trent telling his experiences to a skeptical psychiatrist (David Warner). It's set in a small New England town where the protagonist undergoes a journey where the horrors he encounters drive him mad. Most significantly, the film concerns the Old Ones.
In Lovecraft lore, the Old Ones are a race of monstrous beings beyond description driven from our universe into another realm, where they bide their time until they can return. On occasion, individual humans encounter them, but the sight of any of these creatures is so horrific, they drive a man insane. This is what Cane writes about, and he's so good at it, his readers believe "All those slimy things trying to get back in" are real. As more people lose their ability to differentiate fantasy from reality, the Old Ones gain the power to return. Cane's new novel is the harbinger of the apocalypse.
In the Mouth of the Madness (the movie) is about mass hysteria and how quickly it can spread. The "mouth of madness" is word-of-mouth; Cane's popularity spreads from his books and turns into fanatical obsession. The media play their part, too. Harglow publishes Cane's work even though he knows its effects on people because he makes millions, although he won't read the books himself. There's the news media, showing footage of riots of television and discussing on the radio outbreaks of unexplained violence, contributing to a context of fear and panic.
Cane's power of public's belief in his work allows him to become a god. He even calls his book the "new Bible." His material is pulp horror, but people's belief gives it power, not the ideas themselves. As one character says, "A reality is just what we tell each other it is. The sane and insane can easily switch places." That is the frightening aspect of the movie. Any idea, no matter how crazy or delusional, can gain power if enough people believe it (Just look at the Twilight craze). Cane's words take on a life of their own. Another character puts a shotgun to his head because "He wrote me this way."
One can't help but be reminded of the social unrest gripping America today. Think about Sarah Palin's Facebook comments about "death panels" and how that threw much of America into a frenzy about the health care bill, even though the bill contained nothing about forced terminations or such government panels. Also, look at the Tea Party movement, TV pundits, talk show radio hosts, people showing up at Presidential speeches with firearms, and the spread of radical Islam, and I can't help but think Carpenter was once again ahead of his time.
The creature effects are done by KNB, and we get a wide variety of monsters with tentacles, claws, and slime. While some are obviously rubber, they're not your garden variety man-in-a-suit, and we only catch glimpses of them, so those moments are effective. The moment Cane tears open a door in reality to let the Old Ones pour forth is a particularly virtuoso sequence.
In the Mouth of Madness is one of Carpenter's most ambitious and layered works. Forget Michael Myers, here, ideas are really scary. Mass hysteria and fanatical beliefs are far more powerful than a lunatic with a knife. At one point, Trent says to Cane, "God's not supposed to be a hack horror writer." Note to Scientologists: God shouldn't be a hack sci fi writer, either.