Peanut Butter Falcon, the story of a fugitive on the lam with a young man with Down syndrome, is an affecting, appealing piece of Americana.

Zak (Zack Gottsagen) is an orphan housed by the state in a Virginia old folks home. He slips out one night to pursue his dream of meeting and training with the pro wrestler whose tapes he watches obsessively, and who lives in North Carolina.

He hooks up with a self-destructive young man named Tyler (Shia LaBeouf), an unemployed fisherman who’s hotfooting it out of town because he’s dangerously reignited a long-standing family feud.

Tyler doesn’t want Zak slowing him down, but he also sees immediately that Zak is vulnerable and helpless, and doesn’t like seeing him bullied. A partnership forms. Zak, who is scrupulously candid, wants to be sure that Tyler knows what he’s dealing with, and announces for the record that he has Down syndrome.

“I don’t give a [crap],” says Tyler, and while the response is superficially harsh, its true dimension reveals itself over time. Tyler isn’t saying he doesn’t care about Zak, because events reveal that he does. He’s saying he doesn’t care that he has Down syndrome. He’s going to treat Zak as he would any fellow fugitive, which means that Zak will bear the same risks and meet the same challenges on their off-the-grid trip downriver.

Swimming rivers, building rafts, building fires — Zak (nicely played by Gottsagen) has to be all in for all of it, and though he needs time to adjust to life without an institutional safety net, we see the growth that comes through independence, through meeting challenges he wouldn’t face in a controlled environment.

There is honest sentiment in the arc of this story, aided by the chemistry between Gottsagen and LaBeouf, and by the warm mood of the film, Painterly images of rural byways and misty rivers reinforce references to the literary elements of the story (the script mentions Twain, but Steinbeck is in there too).

The road-movie framework -- with its beautiful, rootsy soundtrack (the Staple Singers, Gregory Alan Isakov, Ola Belle Reed, Sara Watkins, the Time Jumpers, the Piedmont Melody Makers, etc.) of gospel, folk, country, and bluegrass -- along with the overarching themes of what it means to be good and bad, and the impromptu baptisms at times make the film feel like an updated O Brother Where Art Thou?

Peanut Butter Falcon is a more conventional film, and by the time Zak and Tyler reach their destination, it has morphed into a full-on, feel-good fable, but the kind that doesn’t make you feel bad about feeling good.

The performances are solid throughout — Dakota Johnson has never been better as the caseworker who sets out on Zak’s tail, and there are small, vivid roles for John Hawkes, Thomas Haden Church, and Bruce Dern, embellished by contributions from nonprofessional locals who turn up in location shooting and give the movie its distinct and vivid local flavor.

All in all, a very nice late-summer surprise.

The Peanut Butter Falcon. Directed by Tyler Nilson and Michael Schwartz. With Zack Gottsagen, Shia LaBeouf, Dakota Johnson, Bruce Dern, and John Hawkes.

Running time: 1 hour, 33 mins.

Parents guide: PG-13

Playing at: Area theaters.