When a movie credits more than two writers, it frequently means some of them were brought in to resuscitate a script that had no pulse.

"Four Christmases" has not one, not two or three, but four writers. And their combined efforts failed to bring this disappointing movie to life.

Here's the setup: Reese Witherspoon and Vince Vaughn play Kate and Brad, a devoted but happily unmarried San Francisco Bay-area couple. Their usual practice is to avoid family holidays by faking commitments to altruistic Third World missions such as tutoring children in Africa, then secretly jetting off to an exotic vacation.

This time they're caught and forced to go home for Christmas. Because their parents are all divorced, that means four homes. Each visit tends to be more fractious than the one before.

First, they drop in on Brad's dad (Robert Duvall), who also is playing host to Brad's brutal and moronic brothers, Denver and Dallas. Next it's Kate's ditzy and oversexed mother (Mary Steenburgen). Then it's on to visit Brad's unreformed hippie mom (Sissy Spacek), who's blissfully shacked up with one of Brad's best boyhood pals. The sole outpost of parental sanity in the couple's Christmas odyssey is the home of Kate's father (Jon Voight).

Each stop reveals secrets that Kate and Brad would prefer left hidden. The visits also test the couple's commitment to each other and their resolve to remain unmarried and childless. It isn't hard to see where this is going. Unpredictability is not the strong suit of "Four Christmases."

Nor is comedy, at least not the warm and toasty kind. Though there are a handful of exceptions, most of the jokes in "Four Christmases," both verbal and physical, bear a toxic edge that undercuts the movie's advertised claim to family holiday hilarity.

Among its other offenses, "Four Christmases" squanders the talents of its top-level cast. Proven comedy stars Vaughn and Witherspoon seem off their game, as if unsure what to make of the story, and the veteran Spacek and Steenburgen are saddled with roles far beneath their abilities.

Only Voight manages to transcend the material. Unfortunately, his character's quiet, dramatic interlude with Kate comes too late to sweeten this tart holiday brew. Ditto an anemic 11th-hour reunion between Brad and his dad.

Watching "Four Christmases" is like being the kid who yearns for a bike or PlayStation 3 but finds only socks and underwear under the tree.