STEVEN SODERBERGH is a chameleonlike director whose effects depend on visible changes of emphasis--the ambient glow in the background, the blur in the foreground, the slight sway of an unmoored camera. When I was a kid in Glendale, they used to illuminate the stucco apartment buildings with colored floodlights to add drama and the allure of the exotic to these two-up, two-down people hutches.

Soderbergh does this also. Taking a foursquare man, an uninteresting business hotel, a single-wide trailer or a patch of prairie, he lights up his subject and gives a twist of the rheostat, so we no longer feel we know what we're seeing.

His new film, The Informant!--an uproarious, sinister comedy of self-delusion--reminds me of Hitchcock. It's a Hitchcock film with no blatant eroticism; Melanie Lynskey's bare and very soft-looking arms are about the height of sensuality in the film. This is more like the Hitchcock who was fascinated with treacherous men who weave their own doom out of their desire to be nice guys.

The stucco building under Soderbergh's colored flood lights this time is Matt Damon, and he's never been so much fun. Damon is frumped to the max, with a tire around his gut and a ratty, chewed-looking blond mustache. He plays Mark Whitacre, a dweeby denizen of the Illinois Corn Belt with a lovely wife, Ginger (Lynskey, better served by this movie than any other she's been in since Heavenly Creatures), and an indeterminate number of kids: three, maybe two.

The time is the early 1990s, with colossal computer monitors overwhelming desks and brick-size cell phones. The clothes and furnishings are vintage Sears catalog. And the white men we see all have necks like steers.

Whitacre is a vice president at Archer Daniels Midland Company, in charge of cooking up lysine out of corn for the food-additives company. He has discovered a problem: sabotage by Japanese interlopers and a payoff to make it go away. Against Whitacre's wishes, his superiors whistle up the FBI.

Enter a pair of local agents. One is Special Agent Brian Shepard; as the agent, Scott Bakula's solemn Lincolnesque profile rhymes with the busts of the Great Emancipator seen all over the Illinois locations. Mark, urged by Ginger, confesses to Shepard that he knows a secret: ADM and its overseas rivals have been conspiring to fix prices. The FBI urges Mark to wear a wire to try to nail down the schemers.

On his many trips overseas, Mark clumsily gathers evidence. Scott Z. Burns' script doesn't downgrade the importance of the investigation. But when Whitacre claims that the ADM management has been "scared straight" and is no longer price-fixing, Shepard has to force Whitacre into working for the law.

Whitacre is out of it. He believes all the Michael Crichton and John Grisham he has been soaking in during his millions of miles flying around the world. And being a stranger everywhere, he has a tendency to blab to whoever will listen--even the man who blows the leaves off his front lawn. Inevitably, the executive's own foot gets tangled in the trap he's weaving.

Soderbergh's comic thriller, with its Quinn Martin Production exclamation point, shows what was missing from Spielberg's Catch Me If You Can and Michael Mann's The Insider. This film is not weirdly ungrounded in any kind of point of view like the Spielberg, and it's more of a retort than a reply to the humorless, overwrought Mann.

Soderbergh drapes The Informant! in what might be seen as an overeditorializing soundtrack. One doesn't hire Marvin Hamlisch to go small--picking him was likely an act of nostalgia. It's actually a smart move to use music to heighten the comedy of this bestiary of liars. There are career-smart liars--the beefy execs, fretting over the thought that ADM will drop from No. 44 to No. 45 on the Fortune 500. There are the law enforcers, lying by omission for their country. Lastly, there is the out-past-Saturn truth stretcher, Whitacre.

One key to screwball comedy is that everyone in the picture must be either deluded or a fraud. That's certainly the case in this small masterpiece of slyness--a lambent, seemingly effortless entertainment, a slice of cake that has a tarantula on it.

THE INFORMANT! (R; 108 min.), directed by Steven Soderbergh, written by Scott Z. Burns based on the book by Kurt Eichenwald, photographed by Soderbergh and starring Matt Damon and Melanie Lynskey, opens Friday countywide.

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