The biggest difference between Tom Ripley, the duplicitous drifter Matt Damon played in The Talented Mr. Ripley, and Mark Whitacre, the seemingly guileless whistleblower who tries to take down the agricultural giant Archer Daniels Midland in The Informant!, is that Ripley was a homicidal sociopath, while Damon’s Whitacre, whose book smarts are rivaled only by his idiocy in practical matters, is a pathological liar, and a sloppy one at that.

Whitacre, a paunchy Midwestern everyman who sports an unflattering mustache and a comically prominent hairpiece he adjusts whenever the pressure builds, is the subject of Steven Soderbergh’s latest farce. If his story seems unbelievable, as the movie’s billboards loudly suggest, so is the man himself.

Yet he doesn’t seem that way at first. Rather, he comes across as a hero of sorts, acting according to his conscience because it’s the right thing to do. He wants to be the man in the white hat, as he tells his FBI handlers (Scott Bakula and The Soup’s Joel McHale), but it doesn’t quite fit.

He’s happy to out the ADM honchos who are fixing prices for lysine, an essential ingredient in corn-based products. But he neglects to air his own dirty laundry: Even with the FBI tracking his every move, he manages to embezzle $9 million in company funds.

How could this happen? Soderbergh and writer Scott Z. Burns, who adapted his screenplay from journalist Kurt Eichenwald’s book of the same name (minus the cheeky exclamation mark) suggest that Whitacre, a real-life informant, was considered too much of a rube to be taken seriously as a mastermind thief – or a mastermind anything.

Wearing a wire and recording his colleagues as they conspire to bilk the public, he fancies himself a real-life James Bond – Agent 0014, “because I’m twice as smart,” he explains – but Marvin Hamlisch’s goofy score, which cleverly lampoons Monty Norman’s “James Bond Theme,” mocks him at every turn. Whitacre would be a joke if he weren’t capable of doing so much damage.

That doesn’t stop Soderbergh and Damon, who gained 30 pounds for the role, from treating him like one. The comedy is more amusing than uproarious, but Whitacre’s nutty inner monologues – stream-of-consciousness asides that grow increasingly paranoid as the walls cave in – steal the show.

He is diagnosed as bipolar, which helps explain his bizarre behavior, but based on the evidence, a strong case could be made for attention-deficit disorder. Whitacre seems incapable of focusing as his mind races from one scattershot thought to the next. And he's all over the place emotionally, making his usefulness to the FBI that much more perplexing.

He’s an ideal informant, always thinking on his feet and ready with a plausible lie, and the Justice Department’s case against ADM would go nowhere without him. How does he do it? Because, beneath all the B.S. and self-created mythology – Whitacre falsely claims to be an orphan because orphans engender sympathy – he’s cunning. You wouldn’t know it to look at him, or to listen to him, but that’s part of his oddball charm.

With its ’70s-style title cards, hokey score and rambling narration, The Informant! finds Soderbergh returning to the slick, stylized filmmaking he employed in the Ocean’s Eleven series, and it’s an appropriate choice. Whitacre is pulling off a wacky heist caper, scamming anyone foolish enough to take him at his word. It’s surreal, and the movie reflects that.

Does that make The Informant! the equal of Soderbergh’s best work? Not really. It’s never boring, and the humor resonates more often than not, but watching Whitacre bury himself in ludicrous deceptions is a chore; at some point, his madness becomes maddening. What makes the movie work is Damon’s manic performance. His unflagging energy is appealing at first, but seems finally like the last recourse of a man every bit as desperate and pathetic as Tom Ripley.