So … what, exactly, happened?

“Mother of God,” said the assertive bystander. “What kind of terrorists are these?”

“Mother of God,” said the assertive bystander. “What kind of terrorists are these?”

That’s the question asked in M. Night Shyamalan’s newest film “The Happening,” about which the best part is its length: one hour, 31 minutes.

It’s awful, but at least it’s over quickly.

The movie, like any good scary story, starts out at 8:33 a.m. on a Tuesday morning. It’s shot almost completely in daylight, much of it outside amidst lush green fields. No creepy darkness, no damp warehouses — Shyamalan employs none of the usual tricks of the terror trade.

But unfortunately for the filmmaker so well known for his infamous twist in the “I see dead people” favorite “The Sixth Sense,” his latest venture is likely to be remembered only as a flop. When it comes to the Richter Scale of Scariness, this one barely even registers.

“The Happening” follows Elliot (Mark Wahlberg) and Alma (Zooey Deschanel), a young couple on the brink of breakup. He’s a high school science teacher trying to teach today’s youth to think outside the box, and she’s having tiramisu dates with another guy. Though the audience is supposed to be rooting for them to work things out, Wahlberg and Deschanel are so completely devoid of chemistry that if the repopulation of Earth lies with them, humanity may as well be written off with the dinosaurs.

The two are fleeing Philadelphia by train with Elliot’s buddy Julian (John Leguizamo) and his young daughter Jess after word of a terrorist attack hitting the East Coast — one that makes its victims stop whatever they’re doing, stand like a stick of celery for a few seconds and then exert enough mental capacity to decapacitate themselves. In short order, they become willingly suicidal.

While early depictions of this attack are striking — one scene shows construction men walking off a building’s edge in a very haunting, non- “It’s raining men” kind of way — what starts out going down Spooky Lane ends up taking a turn on the Insipid Plotline Highway.

Instead of the usual twists and shocks, the movie plays like a hyperbolized environmentalist’s warning as we discover early on that trees and shrubs are plotting through the wind against the invading human species. Yes, you read that correctly. The plants emit a poisonous chemical that causes people to do themselves in in various disturbing ways, like shove their heads through plate-glass windows or running themselves over with an industrial-sized lawnmower. Gone is the expected and hoped-for Shyamalan-stamped mind puzzle.

It’s campy and shallow, and at times has a realism akin to a junior high play. After their ride out of town goes kaput, Elliot and Alma go running for the hills with the rural Pennsylvania locals. While fleeing, they just so happen to stop for a side character’s speech on the misunderstood nature of hot dogs. Not that I’ve ever been in the situation, but I’m guessing if I’m outrunning an invisible, fatal airborne toxin, I’m not going to stop to listen about the manifest destiny of link-shaped pork.

At another point, while witnessing the deaths of a group of poison victims, Alma faces Elliot and yells “we can’t just stand here as uninvolved observers!” Not only is that probably the most complex sentence spoken in the movie, it’s delivered with a wide-eyed exasperation that simply can’t be taken seriously.

Ladies and gentlemen: There’s even a moment in which Elliot tries to save himself by singing a Doobie Brothers song.

Sure, there are a few successes in the film. One includes a speech from Wahlberg regarding a “completely superfluous bottle of cough syrup,” and another — possibly a shout out to a jump-from-your-skin “Sixth Sense” moment — has the camera coming upon a landscaper’s truck, then a series of ladders and finally a dozen men’s bodies hanging in the trees.

But the real ringer is the setting. How enticing can a film be when its antagonists are America’s fruited plains? While it could be said Shyamalan uses nature as-is to make his audience think, (i.e. Is Mother Nature about to lash out at our polluting population? Has she already begun?) it still stands that it simply doesn’t work.

The film also stars an ill-used and nearly unrecognizable (they grow up so fast!) Spencer Breslin, and strides along at the pace of a host of horrible instrumentals. When it comes to this summer’s blockbuster disappointment list, this one just nabbed the top spot, knocking even “Jumper” out of the race. Despite its intentions, “The Happening” just doesn’t have it going on.