Welcome back to the art of storytelling! "Back to the Future" is a whirling merry-go-round of a movie, in which everything is precisely machined but nothing seems quite safe. It's a wildly pleasurable sci-fi comedy, filled with enchantment and sweetness and zip as only a bona fide summer hit can be.

Marty McFly (Michael J. Fox) is a high school senior who likes to pal around with Dr. Brown (Christopher Lloyd), a mad scientist with a trust fund. It's better than sticking around the house -- his mother (Lea Thompson) is a prudish scold, and his father (Crispin Glover) a pushover who's always getting, well, pushed over.

Doc invites Marty over to the local mall's parking lot one night, where he unveils his latest invention -- a time machine. Circumstances intervene, as circumstances will, and Marty is transported to 1955, where he meets his parents in high school.

"Back to the Future" is basically a one-joke movie, and a sort of stale joke at that: how will a hip '80s kid make out in the '50s? Will Marty's behavior alter the future? So writers Bob Gale and Robert Zemeckis (who also directed) go back to school, working the basics. Most movies today don't even bother to set up the situation -- it's just on to the gags -- and the others have long, windy passages of exposition. "Back to the Future" gets the necessary information out in a briskly efficient opening reel, topsoil for the forest of jokes that follows.

The jokes have all the dizzying, sometimes perverse edge that is the Zemeckis-Gale trademark, irreverent without being mean-spirited (there are some hilarious Reagan gags), with wordplay that can verge on Dada ("Make like a tree and get out of here," one bully says). In the same way that "Splash" and "The Brother From Another Planet" used aliens to make our way of life seem fresh and new again, "Back to the Future" uses the past -- the kids of the '50s are its aliens, puzzled by '80s culture. And as a director, Zemeckis brings energy to every scene -- the way he brings the world right up against short, distorting lenses makes the screen seem like a windshield, and he has a flair for big-canvas cliffhangers.

Most important, Zemeckis and Gale have given the movie a core of feeling that makes real claims on us. For all its comedy, "Back to the Future" is about a kid coming to terms with his parents' inadequacies, a moment familiar to everyone, and the fulcrum in growing up. Zemeckis and Gale ground the story in that emotion -- the laughs are the movie's high points, but the poignance is what keep you inside it, as Marty struggles with his father's weakness, and thinks, for the first time, about being a parent himself.

That struggle makes Fox's McFly more than just another adolescent con artist, takes the burrs off his precocity. Fox is a television actor with a large, expressive face and a wise guy's e'lan; he's got a big TV-style delivery, but he's able here to modulate himself for the movies while making good use of the shortcuts that TV teaches, that way of conveying a character in a few broad strokes. Fox projects intelligence and a self-confidence that can be unprepossessing, but he's found the character's timidity in the script and brings it out. He may have a lingering contempt for his father, but he also loves him. And behind the sunglasses, he's just like him.

Glover plays a definitive Zemeckis-Gale nerd, with a voice like a collapsing accordion, crazy limbs, and hair sculpted by Quaker State. Thompson is attractive as the mom, and the background is spotted with such indelible supporting players as James Tolkan as the high school's bullet-domed disciplinarian and Wendie Jo Sperber as Marty's gawky sister.

But "Back to the Future" is Christopher Lloyd's breakthrough, the first time he has shown that his own brand of nutty intensity can carry a whole movie. Although he's best known for his "Reverend Jim" riff on the TV series "Taxi," Lloyd came to the movies from the theater, and there's more than a little musical-comedy style in the way he throws his gestures straight out to the audience. Even in repose, he makes Doc Brown hilarious. Those big Lloyd eyes lock beneath adventurous brows, his mouth folds out into a bird's bill, and with his big, flapping walk he has an explosive Daffy Duck quality that blows the dust off the mad-scientist cliche'.

Zemeckis and Gale have their shortcomings, among them a tendency to let climactic chase scenes run too long, and in "Back to the Future" they do so again. But they're also a couple of the funniest, most inventive writers around, and their movie is a giddy whirlwind, littered with the detritus of pop culture, DeLoreans and down vests, Chuck Berry and Van Halen, and calculated to surprise.

Back to the Future, opening today at area theaters, is rated PG and contains some sexual themes.