THE UNBELIEVABLE truth about "The Unbelievable Truth" is that this offbeat, accomplished darkish comedy is the feature film debut of its writer-director-editor-producer Hal Hartley, and lead actors Adrienne Shelly and Robert Burke. Casual, clearly inexpensive (Hartley got his $6,000 seed money when his local bank offered a special on low-interest computer loans) but good-looking, it shares some of the moral gamesmanship of "sex, lies, and videotape" and the small-town eccentricities of "Twin Peaks."

During the slick credits, we meet Josh, a mysterious man in Gap-ad black hitchhiking to his Long Island hometown. "Are you a priest?" everyone asks him. "No, I'm a mechanic," he says. What he learns not to say right away is that he's on his way home from prison. Next we meet alienated Audry, a sulky 17-year-old beauty obsessed with George Washington and the imminent apocalypse, lolling in her Lindenhurst bedroom.

These two haven't met yet, but we know right away they're Meant For Each Other.

Despite his misgivings about this potentially dangerous stranger, Audry's father hires Josh to work in his garage, while everyone in town whisperingly wonders just what this ex-con really did. The details are fuzzy by now, but it seems he had something to do with the deaths of waitress Pearl's sister and father.

"Truth" doesn't really run on plot so much as on nuance and oddball detail. At its center is a tangle of economic and moral deal-making. Audry, who observes that "people are only as good as the deals they make," drives a hard bargain with her strict dad about college and curriculum: She'll give up literature at Harvard for communications at the community college if he'll donate the difference to her anti-nuke charity. Meanwhile, Dad's made a deal with Josh: He can keep his job if he won't go near Audry, who has reluctantly become a fashion model. Eventually we get around to the (gasp) truth about Josh, and really, it's a bit of a red herring, but it's been enjoyable getting there.

As the movie's sole sane male, Burke's Josh is an attractive, ascetic enigma, calling to mind Mel Gibson, with subtly threatening bits of Christopher Walken. The women, on the other hand, are all cool, beautiful, rational presences. As Audry, Adrienne Shelly's mixture of hauteur and vulnerability is funny and affecting.