But with an estimated $57 million budget and a major studio behind it, this ecological horror movie from the creator of "The Sixth Sense" and "Lady in the Water" is nothing but a Z-grade thriller with plenty of unintentional laughs and a preposterous storyline about nature gone awry.

"The Happening" begins with a crowd of people in New York's Central Park who go from normal Sunday strollers into maniacal suicidal killers.

At a nearby construction site, workers begin jumping off the building in one of the movie's sillier moments (hearing bodies crash with a thud around one stunned worker sounds gruesome, but it's more hilarious than horrific).

Pennsylvania science teacher Elliot (Mark Wahlberg) and others around the country hear of the killings and think New York is under another terrorist attack. So he, his estranged wife (Zooey Deschanel), their friend Julian (John Leguizamo) and Julian's daughter (Ashlyn Sanchez) board a train to get away.

But as they journey away from Philadelphia, more and more people fall victim to the mysterious toxin in the form of gruesome suicides (this is heavily touted as Shyamalan's first R-rated feature).

(Spoiler alert - although the movie itself reveals this plot twist early.) Elliot and a crazy farmer he meets along the way deduce that it's the plants and grass releasing toxins into the air, a natural defense mechanism for all those centuries of man polluting the air.

This subplot sparks plenty of laughably bad scenes of the trees and bushes rustling in the wind in threatening fashion. You may find yourself thinking, "Watch it! The tree's got a branch!" or "For God's sake, stay away from those magnolias!"

Worst of all, the acting from beginning to end is uniformly stilted, and the dialogue is riddled with apocalyptic clichés. That complaint falls squarely on Shyamalan, who has never been able to direct his actors beyond laughably monotone deliveries.

With such an asinine concept and cardboard acting to back it up, a better title for "The Happening" might be "Attack of the Killer Ferns." Now that sounds like a movie worth seeing.

vince@sltrib.com

The Happening

WHERE: Theaters everywhere.

WHEN: Opens today.

RATING: R for violent and disturbing images.

RUNNING TIME: 91 minutes.

BOTTOM LINE: An absurd horror movie that will have you laughing instead of frightened.