There are so many potentially wrong things with ''Off the Map" that it's a miracle the film comes out right.
This nearly plotless shaggy-dog story, about a hippie family living in New Mexico in 1974 and the IRS man who comes to audit them and never leaves, could and often nearly does collapse into a puddle of self-impressed whimsy. But the talents of the cast -- above all Joan Allen as a lovely, fraught earth mother -- and the graceful attentions of actor-turned-director Campbell Scott bring the film to luminous life. Those of us who first saw ''Off the Map" at Sundance 2003 and still recall the glow it cast are relieved to learn we didn't imagine this desert flower.
That said, the film immediately gets off on the wrong foot with the introduction of 11-year-old Bo Groden (Valentina de Angelis), one of those precocious preteens who's cynically wise beyond her years. She'd have to be, given that her parents have raised her in the middle of nowhere, with no TV, phones, or friends. To pass the time, Bo goes bow-hunting for squirrels, writes to big corporations complaining about fly larvae in their grocery products (thus guaranteeing a steady stream of food crates in response), and dreams of getting a credit card so she can ''buy a one-way ticket out of this hellhole." No insult to the charming de Angelis, but Bo is too cute by half.
Her parents are another story. Dad Charley (Sam Elliott) is in the middle of a depressive funk and hasn't spoken in months; he leaks tears like a wounded cactus. Mom Arlene (Allen) gardens in the nude and scavenges junk accordions from the local dump. The closest thing to a peer Bo has is George (J.K. Simmons), her father's war buddy who at least takes her fishing.
Into this freeze-framed little universe comes William Gibbs (Jim True-Frost), a hapless IRS agent curious as to why the Grodens haven't filed a return in seven years. The short answer is that they haven't had an income in seven years. The longer answer has something to do with the New Mexico light. The taxman understands once he gets a look at Arlene; both his heart and the movie lift off into the ionosphere the moment he comes across her, sans clothes, locking eyes with a coyote in the midst of her carrot patch.
''Off the Map" rambles without apparent purpose, and yet it blooms in emotional impact as it goes -- as William drops out of the rat race and picks up a paintbrush, as Charley climbs out of his depression rung by rung, as Bo contemplates buying a yacht. The film trades that early cleverness in for a slow, warm, human humor, and an appreciation of the benefits and risks of the untethered life. A scene in which the characters sit around the kitchen table while Charley nervously eyes an antidepressant pill neatly captures the dilemma: Can civilization, the very thing that makes you sick, also heal you?
The film is adapted by Joan Ackermann from her own play, and it's easy to imagine this coming off as both intelligent and twee onstage. But Scott, a bristlingly smart actor (''Roger Dodger," ''The Secret Life of Dentists") who also dabbles behind the camera, opens the film up to the light and loping rhythms of the American Southwest. (He's abetted by the able cinematographer Juan Ruiz Anchia.) Faced with this heart-stopping natural beauty, William can only paint and paint, reflecting what he sees on canvases that eventually appear to curve with the planet itself.
Water, or the promise of water -- of where it can take you -- also plays a part in ''Off the Map," and so do mirages that can leave you stranded. Of all the family, Arlene seems most intent on embracing the desert's dualities, to the extent of alienating her husband and daughter. Allen gives an unforgettable performance, one that's lived in rather than thought out, and it breaks the mold of prim rectitude this actress is often imprisoned in by Hollywood.
I don't want to oversell the movie. If you prefer cogent plot developments and characters who behave the way movie characters are supposed to, if you can't slow your metabolism down to a headstrong amble, ''Off the Map" isn't for you. But if you've ever stood under a night sky and felt the earth turning beneath you -- and felt insignificant and elated at the same time -- Campbell Scott has your number.
Ty Burr can be reached at email@example.com.