The cinematic gumbo proves a decidedly indigestible dish in “Venom,” a slasher movie about a bunch of teens threatened in the Louisiana bayou by an evil snake-man conjured up as an unintended side-effect of voodoo ritual. As that brief plot description should tell you, it’s about as silly as a flick of this sort gets. But worse, it isn’t in the least scary. Just frighteningly dull.

Directed by Jim Gillespie, whose sole claim to blame up until now was “I Know What You Did Last Summer” (let’s give him a pass on “D-Tox,” aka “Eye See You,” because that wretched Sylvester Stallone vehicle was never officially released), this effort–penned by a trio of misguided souls–shares with the director’s earlier one the device of putting a bunch of pretty but rather dumb young people in peril of being dispatched by a nasty boogeyman who wields a deadly hook. The difference is that this time around, they really haven’t done anything to “deserve” such treatment. And the villain isn’t an angry fisherman but a grubby garage mechanic named Ray–the despised, absentee father of one of the kids, in fact. He gets bitten by a bunch of snakes recently dug up by a voodoo priestess who’d used them to “milk” the evil from the souls of dying people in the past. The critters promptly transmit all the wicked tendencies they’d sucked from all those sinister souls to the fellow, and he’s gradually transformed into a scaly version of “Halloween” villain Michael Myers, an unstoppable killing machine who mows down anybody he comes upon and ultimately targets the youngsters, the most notable of whom are Eden (Agnes Bruckner) and Eric (Jonathan Jackson), erstwhile lovebirds who’ve broken up as a result of her decision to go to college at Columbia in New York. A chain of bloody demises follows, but nary a one of them is staged with any particular panache, and though there’s a suggestion in the big final confrontation–which incidentally involves a peculiar act of self-sacrifice–that Snaky Ray has some liturgical purpose in mind in all the slaughter, what it might be is never made clear.

There are a few elements in “Venom” that carry a certain charm. A briefly-seen sign on the railway station, for example, tells us that the town where the movie is set is actually called “Backwater.” When we get to see the interior of that voodoo priestess’ house, it turns out to be a place filled with those mysterious, constantly-lit candles that somehow never seem to burn down. (Like the ones that also fill the romantic bedrooms in most chick flicks made nowadays.) And we haven’t had a really good snake-man in movies since Dirk Benedict donned scales in “Sssssss” way back in 1973. But these are but momentary nuggets in a swampy mess of a movie. The script is a mishmash of cliches taken from every other horror movie ever made, the direction is listless when it should ratchet up the energy, and the acting is all of amateur-night quality. (It’s notable that none of the young actors attempt any accents at all; though supposed natives, they sound like Midwesterners, although most of the adults surrounding them affect a Deep Southern drawl with that characteristic Louisiana kick.) The picture is thoroughly mediocre from a technical perspective, too–Steve Mason’s cinematography and Paul Martin Smith’s editing are particularly weak. And James L. Venable’s music score sounds second-rate at best, contributing little sense of menace.

It’s certainly been an unhappy year for Louisiana. Though they can’t begin to approach the unimaginable horror of Katrina, the earlier “Skeleton Key,” with its ridiculous hoodoo scenario, and now this clunker add cinematic insult to the real-life injury of the hurricane. There’s no known antidote for a movie as poisonously bad as “Venom.”