To remain anonymous, the narcotics officers in "A Scanner Darkly" wear scrambler suits.

They resemble biohazard suits, except that that a kaleidoscope of facial features and clothes continuously flash by, making it impossible for any voice- or visual-recognition software to identify the person wearing the suit.

The scrambler suits are significant for two reasons. They represent the main theme of identity loss, and they are writer-director Richard Linklater's rationale for animating "A Scanner Darkly" rather than releasing it as a live-action feature.

A live-action version of "A Scanner Darkly" does exist, because Linklater returns to the type of animation he used in "Waking Life." The technique is called "interpolated rotoscoping," which means Linklater first filmed his cast %u2013 including Keanu Reeves, Robert Downey Jr., Winona Ryder and Woody Harrelson %u2013 as he would for a regular feature, then scanned the footage into a computer and "drew" over every frame.

The technique, which also can be seen in car commercials, is similar to the Photorealism school of painting, except the details are flattened and cartoony. I don't know if anyone has described the look as "photosurrealism," but that's an excellent word for it.

"A Scanner Darkly" is another film taken from the mind-bending literature of science-fiction author Philip K. Dick ("Blade Runner," "Minority Report"). This story is closer to our reality, though. The scrambler suits are the only fantastic elements; remaining plot elements are derived from a government addicted to surveillance that isn't far removed from our own.

The story takes place in Orange County, Calif., several years from now. The latest crack-like drug threatening America is Substance D, which is so addictive 70 percent of the country is hooked on it. The D stands for death, probably because the drug induces so much paranoia most users eventually commit suicide.

Reeves plays Bob Arctor, a narcotics detective posing as a drug dealer. The drug enforcement bureau is so secretive that agents meet wearing their scrambler suits and no one knows each other's real identities. Arctor's supervisor knows him only as Fred, which is how it comes to pass that Fred is assigned to spy on drug dealer Arctor.

The boss seemingly doesn't realize he has just told Reeves' character to investigate himself. Because Arctor has been sampling his own product, though, he can't keep his dual identities straight. Is he Fred or is he Arctor? Or perhaps is he someone else, with Fred and Arctor representing the two hemispheres of his brain?

This conundrum is typical of Dick's writing, but Linklater doesn't know what to do with Arctor's identity issues except to have Reeves narrate about it repeatedly.

Arctor shares a run-down ranch home with his girlfriend, Donna (Ryder), and junkies Luckman (Harrelson), Freck (Rory Cochrane) and Barris (Downey). Barris provides most of the exposition about Substance D, and Linklater and Downey must be aware of the irony that this material comes from Downey's mouth.

Downey's quirky, unpredictable performance gives the movie its spark. His character is the only one that isn't stupefied by the drug. Harrelson is there mostly for comic relief, and Cochrane for tragedy.

The unusual animation does make "A Scanner Darkly" more fascinating than a live-action version would have been. The plot isn't as confusing as it sounds, although the twist at the end is too weak to surprise.

Linklater wants "A Scanner Darkly" to be a thought-provoking, living graphic novel. But he floods the script with multiple meanings and loses himself in the hydra-headed metaphors.

"A Scanner Darkly" works as a curiosity piece, an animated film aimed at adults with a fascinating subject that never reaches its potential.