Few people go to see movies to catch a glimpse of the real world, and with good reason. It's considerably cheaper to look out a window than it is to buy a ticket. While realism in movies is optional, credibility isn't. That's why getting through first-time director Matt Williams' adaptation of Billie Letts' novel Where the Heart Is becomes such a chore. Even on its own whimsical and exaggerated terms, the movie is never believable enough to be involving.

Williams loses his footing early and never recovers. The movie follows dirt-poor Tennessee residents Novalee Nation (Natalie Portman, Anywhere But Here) and her aspiring singer-songwriter boyfriend, Willy Jack Pickens (Dylan Bruno), as they head to Bakersfield, Calif., to improve their fortunes. They couldn't be doing much worse. Novalee is days from giving birth to their illegitimate child and can barely read, and one wonders how far the two will get in an $80 car with a leaky gas tank and a gigantic hole in the floor.

Novalee's California dreaming ends abruptly when she stops for a bathroom break at a Wal-Mart in a small town in Oklahoma. As she returns to the parking lot, both Willy Jack and the car are gone. While waiting for her baby to come, Novalee starts secretly living in the Wal-Mart. She inadvertently becomes a local celebrity when she winds up giving birth in the store. At the hospital, she meets Lexie Coop (Ashley Judd), the nurse who winds up being her best friend. Like a lot of her fellow citizens, Lexie has a silly name and has dubbed her numerous children after desserts (they include "Brownie" and "Praline").

All of this goofiness is supposed to be quaint, funny, and touching. Instead, it gets irritating. A story like this is probably easier to take in print. Novelists like Letts can use several pages to explain away seeming deficiencies in logic (like how Novalee can stay in a Wal-Mart for six weeks despite security cameras and night crews) or to develop characters. Filmmakers have only a few seconds. Neither Williams nor screenwriters Lowell Ganz and Babaloo Mandel (who've written a lion's share of Ron Howard's and Billy Crystal's movies) hail from the Bible Belt, and it shows. The accents for people who are all supposedly from the same region vary and are generally unconvincing. Even worse, all three filmmakers fall back on their TV sitcom roots (Ganz and Mandel wrote for Laverne & Shirley). As a result, the characters don't converse so much as they spit out redneck one-liners that would make Jeff Foxworthy wince. For example, Novalee is excited about living in a house that "isn't above wheels."

All of this might have been forgivable if the characters were more than shallow rural stereotypes. Multilayered stories like this one require a delicate touch that's completely missing here. Williams leaps from light mockery of the eccentric locals to horrific scenes of domestic abuse and even a ludicrous scene in which a character loses limbs in a train accident. Williams also seems to have little idea what to cut or keep from the book. Willy Jack's quest for country music gold is tired, uneventful, and serves only to set up a ridiculous ending.

Judd's sunny presence almost elevates this mess, but there's little she can do with the cheap wisecracks and corny monologues that have "Oscar clip" written all over them. The normally capable Portman, whose grins seem programmed, comes across as affected and stiff. Because the movie never feels emotionally real and takes the intelligence of its audience for granted, Where the Heart Is aims for being heartwarming but the result is more like a blocked artery. (PG-13)