The term dates to the early 1970s. In a nutshell, it was born when an enterprising movie distributor appended some "realistic" footage to the end of an inept slasher film that was shot in Argentina by exploitation filmmakers Robert and Roberta Findlay. The new footage purported to show a production assistant for the film being raped and murdered on camera. With a clever ad campaign proclaiming that this was "the film that could only be made in South America ... where life is CHEAP!", the film's 1975 distributor suggested to the pres that the footage was documentary, rather than fiction. The press, unfortunately, ran with it. However ludicrous it was on the face of things, the ploy turned an unreleasable South American cheapie into a profitable, if disreputable, curio. The film's release title? Snuff, of course.

Ever since then, the "snuff movie" has danced around the edges of popular consciousness. Some people are convinced they've actually seen a commercial snuff film. There's a very disquieting cycle of rape/murder movies from Japan known as the Guinea Pig series, which has fooled many viewers into believing they were watching actual murders in progress. (Anyone who has even a passing familiarity with Japanese pornography can probably imagine what these films look like; reportedly, they fooled Charlie Sheen into calling the FBI on noted horror film authority Chas Balun.) Investigations into allegations of snuff filmmaking have repeatedly come up empty-handed, with everyone from the FBI to cult film enthusiasts reporting that these films -- records of murders committed exclusively for the purpose of the viewer's sadistic entertainment -- don't exist.

So, in an indirect way, we have the Findlays to thank for 8MM, a new opus brought to us by screenwriter Andrew Kevin Walker (for whose work on Se7en I will be forever grateful) and talented hack director Joel Schumacher. Nicolas Cage, a superior actor who has lately performed in a lot of interesting films but precious few really good ones, plays Tom Welles, a private investigator who's called to the lush home of a recently widowed dowager with a disturbing secret. The woman's industrialist husband kept his most private belongings hidden in a tiny safe that was opened after his death. Inside, she found a reel of 8mm film. On the film is what appears to be an honest-to-God snuff movie, shot on the cheap and depicting the butchery of a pretty teenager in sickening detail. Welles is being hired, she explains, in a halting monologue meant to demonstrate her still-resonating faith in the goodness of her late husband, to investigate the source of the film and demonstrate that the girl is still alive, after all.

In order to do that, Welles embarks on a missing person investigation that leads him, posthaste, into the seedy underbellies of Los Angeles and New York City. Welles gets in over his head, retaining a porno shop clerk -- and closet bookworm -- named Max California (Joaquin Phoenix) as a sort of Stygian tour guide. His lovely wife (Catherine Keener) communicates with him from afar, holding the phone up so their infant son can hear his wayward father's voice -- in this way, clean suburban living is juxtaposed with the sour filthiness of the world of dirty movies and the sex trade.

In short, 8MM tries to acquit itself of its own excesses by declaring itself shocked and saddened to find such filth on display. The snuff pic itself is introduced in quick cuts and blurs, with inserts of Cage squirming and wincing as an 8mm projector whirrs away at his side. (Those who are unfamiliar with low-budget porn may nonetheless recognize the same nonaesthetic that Calvin Klein co-opted for a very controversial series of ads a few years ago.)

Elsewhere, the same perverse glee that Schumacher took in those fetishistic close-ups of Batman's codpiece (from Batman and Robin) is in evidence as he proffers glimpses of the porn underground, complete with bondage gear, enema loops, and a masked, half-naked guy called "Machine." No dummies, Schumacher and Walker cover themselves at every turn. As Tom and Max make their way to professional scumbag Dino Velvet's porno headquarters, they walk through Manhattan's meatpacking district, complete with bloody animal torsos slung over shoulders and hanging on hooks. In case you missed the clubfooted symbolism, this clues us in to the fact that the filmmakers think porn -- at least the sadistic, degrading brand that's exclusively on display in 8MM -- is a Very Bad Thing. It's so bad, in fact, that if you dare engage with it, it will corrupt you. "You dance with the devil, the devil don't change," Joaquin Phoenix observes in one of the film's several moments of strained lucidity. "The devil changes you."

Despite the heavyhanded foreshadowing inherent in that line, I imagined, at about the 80-minute mark, that 8MM was actually winding to a close. "Hey," I told myself, trying to consider the film's entertaining absurdity an asset. "This is just a trashy B-movie. It isn't so bad, after all!" Imagine my dismay when the movie turned into Deathwish 1999 and lost me completely. As it turns out, all of the seaminess that came before is just an excuse to get Nick into Dirty Harry mode, rolling up his sleeves and getting medieval on your ass. To borrow a phrase from Mamet, he becomes what he beheld, confident that he has done right.

Now, I don't believe that these explosions of violence are meant to comfort us -- Walker, especially, is far too smart for that. But they're a spectacularly unsubtle dramatization of the film's concerns about the dehumanizing effect of amoral entertainment. (Maybe they have a point, after all -- by the time this film was over, I wanted to kick Joel Schumacher's ass.) In a climactic scene, the face of evil is revealed to be that of an ordinary Joe. The banality of evil -- imagine that.

I'd be willing to forgive the story's obviousness -- and maybe I wouldn't even have see it coming -- if the filmmaking was of a higher order. After all, David Fincher worked grim wonders with a similarly downbeat Walker screenplay for Se7en. Unfortunately, 8MM is by the numbers, a snuff-movie fable that's shot with the comforting sensibilities of a journeyman director. Schumacher is good at showing you the sleaze, but he's not as good at evoking a feeling of dread, or twisting the knot in your stomach. He's not helped much by lensman Robert Elswit (Boogie Nights, Tomorrow Never Dies), who shoots in a monochromatic murk that's hard on the eyes. Even the score by the always exotic Mychael Danna (The Sweet Hereafter) falls flat, particularly in conventional action scenes.

Finally, Walker's screenplay isn't savvy enough about the mechanics of detective stories to make this cohere as a mystery. The early stuff, which recalls Paul Schrader's more grueling Hardcore, isn't bad, although the lucky breaks that crack the case open for Welles stretch credulity. Later on, when he starts marching into ridiculously dangerous situations without taking any precautions at all, the core story dissolves, and all that's left is the picture's bluntly reactionary ideology.

The screenplay pulls itself together in the final minutes, including an oddly touching coda. Despite all my complaints, Walker remains a fairly talented writer, and it's always good to know that someone in Hollywood still wants to make a film mean something. Still, as long as it's embedded in a mainstream multiplex entertaiment that plumbs such depths, this despairing worldview seems ultimately hypocritical. For all their zealousness in declaring that darkness corrupts the human soul, Walker and Schumacher have made a rather ordinary picture with an ironically self-righteous mean streak.