In David Lynch's impressionistic new thriller, Mulholland Drive, the master of the macabre and the bizarre sends a surprisingly sincere love letter to a Los Angeles of a bygone era. Not that there aren't the usual doses of irony, fractured narrative structure and loose ends, forcing the viewer to wonder just what the hell is going on. That's part of Lynch's charm or, as he proved in 1997's Lost Highway, his undoing.

But for a man who has almost always seemed to have a detached irony from his subject matter, and who often indulges in some serious perversions, what makes Mulholland Drive remarkable is how much care he puts into his characters. They are lost souls in a city brimming with them, and Lynch offers them honest opportunities to find themselves. That we're not sure by the end if anyone has found anything is irrelevant. The film's intended loose ends are like dreams themselves: unresolved, disjointed, fragmented, and in waking up, both characters and viewers alike are left to make the puzzle pieces fit.

Lynch (who won the Best Director prize at Cannes) is paying tribute to that classic of Hollywood eras, the 1940s, where the glamour of the city went unnoticed in the brooding cynicism of film noir. If Phillip Marlowe were in this flick, he couldn't be sure if he was detective or client, alive or dead. That's mainly due to a third-act switcheroo in which the director re-casts his main characters' roles, if for no other reason than to paint Hollywood as a land of realities dancing with dreams (which sometimes become nightmares). And trying to figure out just who's dreaming and who's grounded in reality is only part of the fun and intrigue here. Are we living, breathing people, or actors in a movie run by powers way beyond our control? And if we are, who's the producer?

Nowhere is this more apparent in an early scene between an exotic brunette (Laura Elena Harring) and a blonde (Naomi Watts) named Betty. (Bring on the archetypes!) The brunette, with a wisp of a Hispanic accent, has sought refuge in a Hollywood bungalow after surviving a foiled murder attempt and car wreck on Mulholland Drive. Betty is fresh off a plane from the Midwest and is house-sitting in the bungalow for her aunt and plotting her chart to stardom. As their eyes meet, there is instant chemistry, as if they've met before. When Betty asks for her name, the brunette grasps for the first thing she sees coming out of the shower: "Rita," after spotting a poster of the 1946 Rita Hayworth classic Gilda on the bathroom wall. And as Betty warms to the adventure of helping Rita find her identity, she gushes, "This is a dream place!" and later, "C'mon, it'll be just like in the movies!" In Hollywood, identity, as well as reality, are elusive.

In attempting to create a web of lives that can turn from dreams to nightmares, Lynch splats a handful of seemingly disconnected subplots against his canvas to see which ones will stick, but focuses on the story of snotty director Adam Kesher (Justin Theroux) pressured into casting unknown ingenue Camilla Rhodes against his will. This figures prominently when Lynch switches gears in the final act, careening Mulholland Drive through a narrative prism. Suddenly Betty is actually a waitress named Diane at Winkie's diner on Sunset Boulevard, and Rita becomes Camilla Rhodes -- still lovers, but now both aspiring actresses with Adam thrown into the love triangle.

In previous scenes, both the waitress and Rhodes are seen but virtually anonymous, suggesting in retrospect a dream state where minor characters in real life become a part of the dream. All of this happens not long after Rita and Betty have succumbed to their attraction in a lovemaking scene that is amazing in its subdued eroticism -- which makes you wonder whether Lynch is being sincere or just exploiting a male fantasy. "Have you ever done this before?" Betty asks. "I don't know ... have you?" Rita replies. "No, but I want to with you." Things get really weird after that, as Rita and Betty's search provides answers that only lead to more questions and their subsequent identity flips.

Lynch did a masterful job in casting relative unknowns Harring and Watts in the lead roles. They infuse their characters with varying shades of strength, vulnerability and vulnerability that are surprisingly devoid of some of his typical perversions -- no sado-masochism here. Theroux, another subtle choice, is perfect as the smart-aleck director who is too self-absorbed to realize his attitude is his own undoing. But also, as he has so often done, Lynch serves up cavalcade of cameos. The best is Ann Miller, a Hollywood musical icon of the '40s and '50s, as a landlady.

Mulholland Drive originally started out as a TV series project for ABC, which had debuted and canceled Twin Peaks and also passed this time around. No sweat; Mulholland Drive is best left traveled on the big screen.