David Lynch's Mulholland Drive is certain to mean different things to different people. And too certain people, it won't mean much at all. Savor that certainty, because virtually everything else about Lynch's latest is thoroughly uncertain. Lynch's first film since 1999's sweet but slight The Straight Story is a return to form, for better and for worse. Mulholland Drive finds the director at his murkiest and most moody, as if announcing that Straight Story was apparently little more than a momentary detour on the lost highway of Lynch's career. If nothing else, Mulholland Drive is proof that David Lynch continues to be one of the most maddeningly cryptic filmmakers in America, if not the world.

What most films do is fog us a bit in the beginning, teasing us with just a bit of mystery before proceeding to satisfy us with a steady stream of answers (and, eventually, resolution). The pleasure and pain of watching a David Lynch movie is that it's pretty much all fog, albeit a velvet fog, where everything from plot to characters to the film's very sense of time is felt as much as understood, like some sort of seductive but vaguely unsettling texture.

Mulholland Drive is virtually all texture, lush and languorous but devoid of anything resembling cause-and-effect or answers. Virtually nothing is explained and very little makes sense, at least in a conventional sense. What logic there is here is the same sort of nonlinear dream logic in which Lynch has steeped himself since Eraserhead, and later refined in Twin Peaks — hypnotic, occasionally beautiful, and always, somehow, not quite right.

The film begins with an atypically upbeat, candy-colored sequence in which bright, happy teenage boys and girls jitterbug their way across the screen. The kids are positively beaming with youth, cleanliness and promise — and, I suppose, are mostly there as signifiers of whatever passes for ironic counterpoint in Lynch's universe. They're there to remind of us of all the darkly Lynchian creepy-crawlies lurking just around the corner, or sometimes inside ourselves, much like those nasty insects slithering just beneath the surface of the surburban lawns at the beginning of Blue Velvet.

It might be these same jitterbugging kids who come racing around the bend in Mulholland Drive's first sequence and wind up crashing head-on into a parked car in which a nameless woman (Laura Harring) is about to be shot by two nameless men. The car crash saves the woman from the gunmen but sends her into an amnesiac state that sets her to wandering about the hilly outlands of L.A. with absolutely no idea of who she is, where she's coming from or going.

Like something out of "Snow White," "Goldilocks and the Three Bears" or so many other fairy tales, the woman with no memory finds her way to an empty bed in a house in the woods and immediately falls into a deep sleep. When she awakes, she finds herself in the company of Betty (Naomi Watts) an aspiring actress who appears to be the nameless woman's opposite in nearly every way. Betty is blond, blue-eyed, sinewy and almost unnaturally perky and wholesome.

The nameless woman, now named Rita, is dark, voluptuous, full of secrets and seems to be sleepwalking even when awake. Lynch makes the most of the glaring differences between his two heroines — who quickly become best pals — and then casts them off into the void for the anti-adventure that consumes most of Mulholland Drive's two-and-a-half hour running time.

Rita and Betty's big adventure is basically one of those metaphysical identity games that makers of art films love to devise (but which few really do well), where the pair play Nancy Drew and literally try to find out who Rita really is. "It'll be fun," says Betty. "We can pretend to be someone else." The line just about sums up a movie in which almost everyone, from the bona fide amnesiac to the most together character, is a cipher — a blank slate on which we're invited to project our own fantasies and preoccupations. It all takes place in an L.A. that Betty quite appropriately calls "this dream place," all the better for engaging in some serious make believe.

The weirdo detective story with Betty and Rita is sporadically diverting stuff on its own, but Lynch seems compelled to mix it with lots of completely unrelated elements that wind up making the film seem padded and more pretentious and confused than it might otherwise have been. We get an extended scene out of nowhere in which two men simply sit in a dumpy restaurant, awkwardly discussing an ambiguous (but not particularly interesting) dream. There's even an eyebrow-less guy in a ten-gallon hat who periodically appears in order to deliver some vaguely ominous, mystical instructions by the light of the moon.

Lynch's biggest miscalculation is throwing in a dull tangential plot strand about an arrogant young filmmaker (Justin Theroux) hiding out from some shadowy types who seem to be trying to wrest control of his movie. Word has it that Mulholland Drive was originally designed as the pilot episode for another Twin Peaks-styled television series. One can see how the storyline featuring Theroux's filmmaker might have played better on the small screen, as separate and relatively self-contained segments distanced from the primary plotline with the help of conveniently placed commercial breaks. On the big screen, though, these portions of seem forced and trivial. The filmmaker's story eventually intersects with that of the girls (sort of) but it retains the feel of an unnecessary red herring in a sea of far more interesting red herrings.

Lynch has never been too good with endings, and the one in Mulholland Drive is not going to radically alter his batting average. After a brief lesbian dalliance and a visit to a strange performance club where everyone lip-synchs in Spanish, the film's final half-hour basically turns into a whole new movie, one in which all of the characters change places, names and personalities — not unlike a mutated version of what Bergman did 35 years ago in Persona. It's not clear if this final half-hour is intended as a dreamy alternate to the movie that's been unspooling up to this point, or perhaps as the "real" version of the dream we've been watching for the past two hours.

In any event, it's all from left field, and similar to the convenient cosmic meltdown that ended Lynch's Lost Highway, in which the main character's psyche suddenly fragments under 10 G's of metaphysical hoodoo. And much like the ending to that earlier Lynch outing, this one also strains at significance.

The material that comprises Mulholland Drive isn't exactly fascinating in and of itself, but it's all rendered in a way that's as inexplicably watchable as any dream. There's a relentless, slow-motion car-crash momentum at work here. We can never quite make up our minds if the undercurrent that runs through the entire movie is simply single-minded and lugubrious — like a small reptile crawling along with a limb missing — or perhaps just plain malevolent. In any event, it's the mood of Mulholland Drive that sustains us even when the nuts and bolts of the film seem to be coming apart.

Lynch's big problem here comes down to the notion that he often seems to be dangerously close to repeating himself. Fans probably won't mind, since the director has the good taste and sense to offer up what amounts to a Greatest Hits of his own best moves. The dwarf from Twin Peaks even shows up at one point, for heaven's sake, seated in a spatially distorted chamber way too similar to the room featured in the TV series. None of this exactly disguises that Mulholland Drive, engaging as much of it is, sometimes seems built from a collection of oddly familiar riffs, twitches and attitudes. It's easy to relish those riffs, and the sheer oddness of this spiraling enigma of a movie, but Mulholland Drive never bothers to provide itself or us with an anchor, and the center does not hold.