Al Fountain is a congenital engineer with a pocket of pens and mid-life crisis that would choke a tortoise.

With his latest out-of-town assignment canceled just a few days short of completion, Al (John Turturro) decides not to fly home to celebrate the Fourth of July with his wife (Annie Corley) and son (Alexander Goodwin), but to drive around Tennessee looking for Lake Splatchee, a water amusement park where he spent a few happy days as a child.

John Turturro has given us a wealth of offbeat characterizations since he first appeared at a table in Raging Bull: the sociopathic Heinz of Five Corners, the obsequious Bernie of Miller's Crossing, the manic but loving father Sid Lidz of Unstrung Heroes. So what he saw in the quirky road comedy Box of Moonlight -- a sort of Queasy Rider -- is not easy to fathom.

Al Fountain is not one of the great characters of literature: in fact, he's one of its most worn-out stereotypes: the engineer who lives by the clock, thinks in decimals and has faith in nothing but flash cards. Al is so repressed that even Turturro can't breathe life into him. It takes a Daniel Boone wanna-be named Bucky the Kid (Sam Rockwell) to do that.

Bucky is a pseudo-survivalist who lives in half a trailer near Knoxville and makes his living by recycling lawn ornaments -- without the knowledge of the previous owners. He's everything Al is not, but even this doesn't surprise us, because characters like Al always run into characters like Bucky. It's been that way since Yin met Yang.

Yet Box of Moonlight is not without its delights.

The opening shots of the Great Smokies, with the camera skimming the treetops and a harmonica airing out a breezy tune, set a tone that's both upbeat and whimsical. And then there's Al's moment of truth, when his first gray hair falls from his head and boings on the shower floor.

Director Tom DiCillo plays a few nifty tricks with Al's head as well. The best is a recurring motif in which Al suddenly sees something happening backward: water being sucked up from a glass to a pitcher, a boy on a bike pedaling forward but going backward.

There's some effective social satire, too, as when a fast food chef starts a furor by spotting Jesus in his signboard flames. And there's the box of moonlight itself, which contains the film's one real surprise. Here's a hint: it's not moonlight.

But like its protagonist, Box of Moonlight spends most of its time driving around in circles. It's no surprise then when it, like Al, ends not far from where it began.

With a little more originality, Box of Moonlight might have been just quirky enough to give us something new and memorable. As it is, its tiny delights add up to one big disappointment.