Some people, it’s rumored, enjoy watching films through a drug-induced haze; that was certainly the case back in 1968, when not a few viewers discovered to their delight that the best way of experiencing the last reel of “2001: A Space Odyssey” was in a somewhat altered state. For those who don’t feel the inclination to indulge, Paul Thomas Anderson now offers the next best thing with his adaptation of Thomas Pynchon’s “Inherent Vice.” He presents the novel’s convoluted story in a woozy, vaguely hallucinatory visual style that’s entirely appropriate given its source—and the fact that the perspective is that of its protagonist Doc Sportello, a P.I. in 1970 L.A. whose investigation of a wildly complicated case is clouded by the fact that he’s constantly high on something or other. The result is rather like “Chinatown” with a buzz, or Hammett or Chandler on acid.

Sportello, played in amusingly benumbed style by Joaquin Phoenix, is introduced in his digs in California’s Gordita Beach, where he’s visited by Shasta Fay Hepworth (Katherine Waterston), an erstwhile flame who enlists him to find her current squeeze Mickey Wolfmann (Eric Roberts), a big-time real estate developer. She’s concerned that his disappearance is the work of his wife Sloane (Serena Scott Thomas). When Doc ventures to various locales to look into the matter, he’s ultimately knocked out, waking beside a corpse under the gaze of Detective Christian Bjornsen, aka Bigfoot (Josh Brolin, as ferocious in his flat-top as Phoenix is laid-back with his shaggy mane and mutton chops).

After a weirdly unfocused interrogation, Doc is sprung by his lawyer Sauncho Smilax (Benicio Del Toro), who also tells him about the Golden Fang, of which he’s already been warned by Jade (Hong Chau), who proceeds to reappear in various guises throughout the movie. The Golden Fang becomes a leitmotif that’s identified differently from episode to episode but has something to do with a ship that in turn is connected with a drug operation with which a crazy dentist named Rudy Blatnoyd (Martin Short) is involved. When Sportello goes to Blatnoyd’s office in a building that just happens to be shaped like a Golden Fang, he’s surprised to find there Japonica Fenway (Sasha Pieterse), a whacked-out ingénue whom he once rescued and returned to her powerful fixer of a father, Crocker (Martin Donovan).

Meanwhile, Doc is pressured by Bigfoot and the FBI to locate not just Wolfmann but Coy Harlington (Owen Wilson), a saxophonist who’s presumed dead but shows up occasionally as an activist agitator (though he might be an undercover informant), whose wife Hope (Jena Malone), a former addict now going straight, is anxious to find him. Throughout all his peregrinations Sportello keeps up contact with his current flame, Deputy D.A. Penny Kimball (Reese Witherspoon), who also serves as an occasional source of information and whose straight-laced manner eventually breaks down one night.

There will undoubtedly be those who attempt to figure out the interconnections among all these plot strands in “Inherent Vice,” but even a herculean effort is unlikely to succeed, not only because they’re haphazardly drawn but because much information is fed to us via narration—not Doc’s, as one might expect from the old noir model, but from a secondary character, Sortilege (Joanna Newsome), an old assistant of his who pops up on the beach over the course of the picture and provides some sort of transition from one episode to the next. And precisely how reliable the information she dispenses might be is open to question.

No, the way to enjoy the movie is simply to go with the flow, as it were, and accept it as a trip down the rabbit hole of seventies America, a woozy wonderland of sex shops, hippie dives, new-agey “treatment” centers, Japanese diners (where Bigfoot wolfs down plate after plate of pancakes), windswept desert subdivisions and dank underground chambers, all inhabited by zonked-out characters with names like Petunia Leeway, Buddy Tubeside, Punk Beaverton, Dr. Threeply and Agents Flatweed and Borderline, and where anything can happen and nothing that does—even death—seems to matter all that much. With the help of his creative team—production designer David Crank, art director Ruth De Jong, set designer Anthony Parillo and decorator Amy Wells, costume designer Mark Bridges and cinematographer Robert Elswit—Anderson presents this landscape of misfits as a hallucinatory time capsule oozing with period atmosphere and marijuana smoke, all served up in the company of music by Jonny Greenwood supplemented by an array of eclectic pop pieces.

And his large cast falls in with the vision, led by Phoenix, whose perpetual air of befuddlement doesn’t entirely obscure Doc’s underlying sincerity in burrowing toward the truth, and Brolin, whose manic intensity is the perfect counterpart to Phoenix’s laid-back tude. Among the others, Wilson stands out, his surfer-dude persona fitting effortlessly into the movie’s stoner vibe, and Short’s shtick adds a touch of hyperventilated energy to the proceedings. But everyone throws himself into the swing of things, often in what amount to little more than cameos.

It takes a lot of chutzpah for a filmmaker to attempt an adaptation of anything by Pynchon—even his more accessible works. Happily, Anderson proves equal to the task, and the outcome is a loopy fever-dream of a movie that recasts the conventions of noir in a blissed-out psychedelic haze.