William S. Burroughs famously said there's one mark you can't beat, the mark inside. Perhaps he also ought to have included hellbeasts and horror writers whose books alter reality. A canny insurance investigator played by Sam Neill in 1995's In the Mouth of Madness finds himself up against just such an opponent and his years sniffing out dubious insurance claims are of no help. The third and final film in John Carpenter's Apocalypse Trilogy, it's the most superficially Lovecraftian though it doesn't as effectively tap Lovecraftian horror as the first film in the trilogy, The Thing. In the Mouth of Madness is the weakest of the trilogy but it is not without charms.
We're introduced to Sam Neill's John Trent in an asylum where he's locked away, raving, getting a lot of mileage out of one black crayon, before David Warner shows up to interview him. Trent tells his story and he's introduced again, decimating a phoney insurance claim. He seems like he's modelled a bit on Walter Neff in Double Indemnity and the oddly 1940s hairstyles of some of the women in the film and some of the banter he has with Styles (Julie Carmen) pleasantly recall classic films noir, an interesting shift in tone from the first two films of the trilogy.
Styles is an editor for Jackson Harglow (Charlton Heston) who publishes the works of author Sutter Cane (Jurgen Prochnow). Cane seems to be a cross between Stephen King and H.P. Lovecraft, his books about tentacle monsters and Old Ones being obvious Lovecraft references but he has the vast commercial success and celebrity of a Stephen King.
Trent is brought in apparently to track down Cane, who's gone missing. Harglow is submitting an insurance claim worth millions of dollars to recoup costs from merchandising and sold overseas rights to a book Cane didn't deliver before disappearing. Trent thinks he smells a rat, he thinks it's a publicity stunt, though I'm not sure why he thinks a major publisher would commit such obvious insurance fraud for a publicity stunt.
He eventually realises there's a map of New Hampshire hidden in the covers of Cane's books leading to his frequently used and perhaps not so fictional town, Hobb's End. Harglow sends Styles with him to investigate.
Hobb's End, with its variety of weirdness, feels actually more like Stephen King's Castle Rock than any of Lovecraft's towns but there are several clear references to Lovecraft, including a hotel called Pickman with a painting inside. And there's a church somewhat resembling the one from "The Haunter of the Dark".
I rather wish the film had played around more with Trent's cleverness, playing up the Walter Neff inspiration and have his schemes and insights deployed throughout the story but once the supernatural stuff is set in motion he doesn't have much to do except insist he doesn't believe in the supernatural and no-one pulls his strings.
But the real flaw in this movie is that Cane's writing seems to be coming to life. I almost always find this kind of story a bit tedious and redundant. So the story within a story just turns out to be a story. It's all still fiction to me. Though it wouldn't be so bad if the concept were a springboard for something. I think this device is one of the weaker points of the Doctor Who serial The Mind Robber but at least that story uses it as fodder for something else. In In the Mouth of Madness, it basically takes away Trent's distinguishing characteristics and brings everything to a stop except the running around, which feels pretty pointless once we realise Trent is dealing with omnipotent forces.
It's true, Lovecraft's work very effectively uses some godlike beings, but even Cthulhu and Nyarlathotep are bound by rules that give a main character a chance for escape, even if those boundaries happen only to be disinterest or distance. Like Alfred Hitchcock said, it's the bomb ticking under the table that puts the audience on edge, not the actual explosion.