How maddening "Dune" is! As you would expect from visionary director David Lynch, it is a movie of often staggering visual power, the most ambitious science fiction film since "2001"; it's also stupefyingly dull and disorderly. "Dune" doesn't get going till fully two hours have elapsed, so only the most patient will wait for the images to build to their crescendo. Lax in its storytelling, "Dune" gives us sublimity unmoored.

Based on the '60s cult novel by Frank Herbert, the "Dune" plot is "Star Wars"-simple in outline. The forces of the House of Atreides are gulled by the Emperor of the Known Universe (Jose' Ferrer) into invading the Harkonnens, with whom the Emperor is secretly allied; Paul Atreides (Kyle MacLachlan), scion of the noble line, endures this baptism by fire and grows to manhood.

But Lynch, who also wrote the screenplay, has cluttered his story with taxonomic gibberish and a benchful of unnecessary characters. In the book, it's texture; in the movie, it's lard. Instead of using the book, Lynch is smothered by it -- he tries to bring its 500-plus pages whole to the screen, glossary and all. "Dune" freaks will enjoy seeing such characters as the Shadout Mapes, the Atreides housekeeper, made flesh (by Linda Hunt), but what does she do to advance the story? The same could be said for Max von Sydow (the planetologist Dr. Kynes), Virginia Madsen (as the Princess Irulan) and the rest of "Dune's" crowded cast. In its fealty to those who have read the novel, "Dune" insulates itself against those who haven't.

Worse, Lynch seems to realize how centrifugally confusing his movie is, so he includes every clunky expository device in the screenwriter's manual, from reports studied by the combatants to explanatory voice-overs. Through them we learn that the battle takes place on the planet Arrakis, known, for its aridity, as Dune; Arrakis is the only source of a spice called "melange" that extends life, expands consciousness and enhances intergalactic travel by "folding space." The spice is protected by huge sand worms up to 400 meters long; for the Imperial spice miners, they're a threat, but for the Fremen (whom Paul ultimately joins) they're an ally. Like the book, the movie is about coming to terms with nature, but the subtle way Herbert interweaves his ecological and vaguely leftist sympathies (the Fremen are guerrillas battling against a corporate state) is mostly lost here.

"Dune" focuses on Paul's spiritual journey as he becomes the long-awaited Messiah, the "Kwisatz Haderach," who sees the past and the future in dreams. In the movie, Paul's prescience is expressed in pretentious dream sequences full of eyeballs and droplets falling into puddles and outstretched palms and cackling heads. When he tires of such obliquities, Lynch comes straight out with wisdom for the Dune-atic fringe: Paul learns that "he who destroys a thing controls a thing," "the worms are the spice" and other helpful household hints.

With his clean good looks and thick head of hair, MacLachlan plays Paul Atreides with the bland earnestness of a generic sci-fi hero (will there ever be a last starfighter?); all those brawls and dreams never seem to change him any. It's enough to make you root for the Harkonnens, whose grotesque appearances bring out the best in Lynch's imagination. Lynch has studded the face of the evil Baron (Kenneth McMillan) with a collection of lesions, scabs, cysts, pustules and buboes the likes of which hasn't been seen since those Army VD films; and just in case you didn't notice, Lynch has a physician puncture them with a hypodermic while the Baron barks orders to his underlings, Feyd (Sting), Rabban (Paul Smith, who pours old Ernest Borgnine into new bottles) and Piter (Brad Dourif, whose fright wig and neurasthenic pallor would make a vivid Hamlet). For Lynch, physical deformity makes evil palpable, whether that evil be urban anomie ("Eraserhead"), Victorian hypocrisy ("The Elephant Man") or the corruption of power ("Dune"). And in "Dune," as the self-levitating Baron floats around gleefully while Sting cranks up his crazy, eyebrow-arching grin, Lynch discovers that quality of evil that is most chilling: its playfulness.

As the action moves from the girder-clad industrial wasteland of the Harkonnen empire to the Renaissance splendor of the Atreides' to the plain majesty of the desert (photographed masterfully by Freddie Francis), the sheer imaginative scope of "Dune" can knock you out; the movies haven't seen such stunning architecture since the heyday of German Expressionism. And some of the optical effects, particularly of the Atreides' shields (which transform the bearer into cartwheeling geometric crystals), make "Star Wars" look tacky. Lynch can find poetry in quick, almost discarded images, like a brief, awful glimpse of a child holding a dagger.

Over the course of the movie, the worms come to occupy "Dune's" visual center. As they pound through the sand (was slow motion ever used so artfully?), their three jaws yawning hungrily, they achieve a blank, unutterable grandeur. But the force of these images isn't attached to anything; while Lynch can achieve effects beyond the ken of most of his contemporaries, he lacks the most rudimentary knowledge of narrative. You leave "Dune" feeling a kind of awe, but wondering what it was all about. "Dune", opening today at area theaters, is rated PG-13 for violence.