Released this week on DVD: "The Informant!"

Grade: A

No subject is more vital yet more difficult for filmmakers to dramatize than corporate power, which extends like a slimy octopus across national boundaries and electoral tides. Director Steven Soderbergh was able to harpoon the creature with Erin Brockovich because the bait was a heroic hottie played by Julia Roberts. In The Informant! the lure is Matt Damon with a potbelly and a bad mustache, yet it works just as well.

By turning a whistle-blower into a tragicomic figure, Soderbergh sustains our interest in a complicated financial scheme and rewards it with a kickback of ghastly laughs.

The facts are these: In the early 1990s, executives at Arthur Daniels Midland, operating out of Decatur, Ill., conspired to control the price of a feed additive called lysine, thus inflating the cost of countless consumer goods. An ADM employee named Mark Whitacre went to the FBI, which persuaded him to record hundreds of secret meetings.

But it turns out that Whitacre's motivations were more complicated than mere moral outrage.

As portrayed by Damon, Whitacre is the anti-Jason Bourne, a married Midwesterner who thinks he's an international man of mystery. After he contacts the FBI, Whitacre plays the spy game like a Little Leaguer, winking at the hidden cameras.

The Informant! echoes with mordant laughter in the chasm between Whitacre's mundane reality and the action-hero fantasy implied by the exclamation point in the title. What lifts the film above facile irony is the growing suspicion that Whitacre's blundering may be symptomatic of something darker. By the last act, this ostensibly centered man is going over a cliff in slow motion, and not in a James Bond sense.

When he crashes to earth, Whitacre's shattered credibility distracts us from the much larger mess made by his employers. But the movie's skewed focus is understandable. Faced with the choice to entertain or inform, Soderbergh trades the big picture for a fascinating portrait.