Just when you thought your post-9/11 paranoia had reached its peak, along comes "A Scanner Darkly," catapulting you back to the future of Philip K. Dick's darkest sci-fi vision. Rendered in Richard Linklater's weird Rotoscope animation, it makes your skin crawl -- literally -- from the opening moments.

	Keanu Reeves is Bob Arctor and Winona Ryder is Donna Hawthorne in director Richard Linklater's "A Scanner Darkly," based on the Philip K. Dick novel. Click photo for larger image. 'A Scanner Darkly' Rating: R for drug and sexual content, language and violent images. Starring: Keanu Reeves, Robert Downey Jr., Winona Ryder. Director: Richard Linklater. Web site: www.scannerdarklymovie.com/

That would be the scene in which a doper named Freck (Rory Cochrane) wakes up to the itch of a bug crawling on him. Make that two bugs. No, it's 200. Or 2,000 of them. The more frantically he tries to scrape them off, the more hideously they multiply in his drug-addled brain.

Freck, like most people in this grim futuristic Orange County, is addicted to Substance D, the mega-drug of everyone's choice. Actually, they have no choice in the matter. An evil cartel has made sure that Substance D -- a kind of psychedelic hybrid of crack, crank and X-tasy -- is in universal demand and universally in control of the populace, despite the Big Brother government's efforts to stop it.

Keanu Reeves is Bob Arctor, a D-addict who is simultaneously an undercover narcotics agent. Talk about conflict of interest: He has to spy not only on his crazy roommates, Barris (Robert Downey Jr.) and Luckman (Woody Harrelson), but also on himself. His superiors don't know about his double identity because narcs have special "scramble suits" that constantly change their forms and faces, thus foiling the ubiquitous scanner devices that otherwise track and keep everybody in line.

This morphing process, which overlaps the live-action performers with animated highlights, poses almost as much of a problem for the audience as for the authorities. Linklater used that painstaking Rotoscope technique to excellent effect in his "Waking Life," and here, too, it achieves the goal of blending (and confusing) hallucination with reality. The perceptual distortions are often fascinating. But don't see "Scanner" if you're epileptic -- a headache, if not a fit, might be in store.

If the visuals are sometimes annoying, so is the leisurely pace. Unlike "Blade Runner" and "Minority Report" (et al. Dick stories adapted to the screen), "Scanner" is extremely faithful to the source and will appeal to science-fiction purists. But folks who don't know and adore the original text are likely to find it confusing and too talky, putting all the "Big Issue" philosophical concerns (drugs, free will, personal identity, institutional tyranny, etc.) above the drama.

If Linklater had taken the opposite approach, he'd have been criticized for that, too. Dick's book was, in many ways, a more factual than fictional account of how he and his friends disintegrated from drug use in the '70s. "I am not a character in this novel," he said. "I am the novel."

As such, it lacks much razzle-dazzle "action" (and contains less actual violence, overall, than "Bambi"). But it contains a wonderful speed-freak performance by Downey as Keanu's fey, untrustworthy friend, and Cochrane adds crazed black-comic relief as the bug-infested Freck. Reeves and Winona Ryder, on the other hand, work hard to provide the current slacker cachet.

Bottom line: It's fascinating, but I wonder if we couldn't have seen just as clearly or darkly through this "Scanner" without the animated ornamentation.

Opens today at the Oaks, Oakmont.