GRADE: C

It's a terrific idea for a movie. Kyle MacLachlan and Elisabeth Shue play Matt and Annie, an unremarkable couple raising a baby and renovating their house in the Los Angeles suburbs. Matt's a fundamentally decent fellow, albeit stuffy and insecure. Annie is that wonderful combination of motherly grace and sexual brushfire, but she's unappreciated by her husband, who's consumed mostly with himself. Into this stable but stale relationship trips Joe (Dermot Mulroney), Matt and Annie's down-to-earth friend with a distinctly rough-hewn charisma. Naturally, Joe represents everything that's missing from Annie's life, and winds up shooting some trouble for the couple and getting under Matt's skin.

I'm sorry -- that's not a terrific idea for a movie, although it's not a bad one. The catalyst here, the brilliant conceit that makes events move, is that old dramatic standby, the blackout. The lights of L.A. are knocked out, not by your run-of-the-mill power failure, but by some relative cataclysm that takes out power in a handful of western states and simultaneously scrambles the telephone lines. The neighborhood becomes something reminiscent of a war zone, with human kindness in as short supply as batteries and gasoline. Neighbors stalk through their front yards carrying flashlights and guns, and the community gathers for strategy meetings.

Writer and first-time director David Koepp (his writing credits include Jurassic Park and Mission: Impossible) relies on mood, atmosphere, and thoughtful plotting to make the sense of widespread fear and desperation palpable, since he's got no budget to speak of. (Independence Day, which was throbbing loudly in the theater next door, is nowhere near as good at setting a mood of panic.) From the very first scenes, you can tell that Koepp's not in complete control of his material; the performances seem forced, as though the characters are marking time waiting for something to happen.

But before long, it starts working. The narrative is made up of steadily mouting challenges to Matt's competence as a lover, a parent, and a husband (that is, his very manhood) -- when his child falls ill, he must figure out how to get his hands on amoxicillin; strapped for cash, he has to negotiate to buy a gun. Those challenges are personified in Joe, who visits to help hold down the fort, and gets to know Annie a little too well for Matt's taste. Annie, meanwhile, is a shameless flirt, at least with the lights out. Shue's open sensuality is perhaps the best thing about the movie; even if her character seems drawn mainly from her own award-winning turn in last year's Leaving Las Vegas, she's an absolute pleasure. Mulroney isn't quite as natural, but the movie starts to pick up speed as soon as he comes on screen. For one thing, his nuts-and-bolts presence is a welcome relief from MacLachlan's one-note performance.

Years after being used to such good effect by David Lynch (in Blue Velvet and Twin Peaks), MacLachlan seems to have settled into a new groove, playing charmless characters (c.f. last year's execrable Showgirls). MacLachlan's Matt is the kind of petulant bonehead who gives the suburbs a bad name. The script never quite shows what makes him tick, but the way MacLachlan plays the role, he surely thinks he's entitled to something -- in this respect, The Trigger Effect echoes nothing so much as Falling Down, in which Michael Douglas played The White Guy Who Couldn't Take It Anymore. (The Trigger Effect also shares some of Falling Down's weird racial subtext, twice pitting the white guy versus the ethnic other.) It's a miscalculation that distances the audience from Matt's dilemma.

Even so, Koepp is a skillfull craftsman, and The Trigger Effect is a surprisingly taut thriller in spite of its flaws -- until it takes a horribly wrong turn. At about the two-thirds mark, the trio make a decision to hit the road and drive until they reach a family member's home in Colorado. Before long, there's a confrontation on the road, and events are thrown topsy-turvy as Koepp makes a clumsy grab at deeper meaning. (One of the end credits helpfully points out that the story is inspired by the old PBS TV series Connections, one episode of which looked at the impact of a similar blackout in the Northeast.) In the process, the triangle that gives the movie its structure is completely dismantled in favor of a sharper focus on Matt. It's unexpected, sure, but it's here that the movie loses its bearings, and its laborious proceedings become too much to swallow.

The final straw? Well, you'd expect Matt to have learned something from his own stupid decisions, but his role in the hysterical, highly improbable climax makes you wish somebody would shoot him just to stop his shouting. What a comedown. Wish Koepp better luck with his next effort.