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, 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 Hitchcock with no blatant eroticism; Melanie Lynskey's bare and soft-looking arms are 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. And moreover it's the kind of Hitchcock you don't want to write too much about for fear of giving away the store.

The stucco building under Soderbergh's colored floodlights 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 amount 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 for his company, Mark clumsily gathers evidence. Scott Z. Burns' script doesn't downgrade the importance of the investigation. As Whitaker puts it later, it's as if ADM were robbing every grocery store in the nation. But when Whitacre claims that the management has been "scared straight" and is no longer price-fixing, Shepard has to force Whitacre into working for the law.

Whitacre is a kind of genius in his field—a Ph.D. in biochemistry who moved to the executive side, the youngest VP in the company's history. But he's also a free-associater: Leopold Bloom self-intoxicated by interior monologues about everything from pellagra to frequent flyer miles (but without Bloom's serious interest in sex).

Being a stranger everywhere, Mark has a tendency to blab to whoever will listen. Inevitably, the executive's own foot gets tangled in the trap he's weaving, and Whitacre must recruit his own lawyers.

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, like the slightly psychedelic 1970s typeface of the film's titles. The effervescent music recalls Hamlisch's Bond score and the warped Dixieland he composed for Woody Allen's Bananas. The big soundtrack chases out any unwanted memories of Fargo—a movie that rhymes with The Informant! but doesn't overlap. 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. 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, photographed by Soderbergh and starring Matt Damon and Melanie Lynskey, opens Sept. 18.

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