Would you buy a car from this man?

"Slasher" could be a David Mamet stage drama. It's a dark portrait of American capitalism, as it plays out on the overheated lot of a Memphis car dealership. It's filled with crude sales rhetoric, marketing ruses, male bonding, and ethical blackouts. And at the center of "Slasher" is a classic Mamet figure, a verbal spewer who once was in jail and is still imprisoned by his ego.

But "Slasher" (which premieres tonight at 10 on cable's Independent Film Channel) is a documentary, an unscripted story of commercial aggression and consumer ignorance. Wittily directed by John Landis ("Animal House," "The Blues Brothers"), it focuses on one week in the life of a gonzo salesman named Michael Bennett, who is a price "slasher" by trade. Basically, Bennett is hired by car dealers to conduct radical weekend sales events, over which he reigns like a ringmaster at a circus. With a DJ, an assistant, and a crew of sexy hostesses, he transforms car lots across America into hyped-up environments where ordinary people suddenly feel willing to sign away their life savings.

The movie reveals a few car-sales tricks, beyond the balloons, banners, and caution tapes that attract potential customers to the lots. Bennett does indeed slash prices before buyers' very eyes, but those prices were inflated only days earlier. It's all about "what you think you're getting," he explains. As you watch Bennett and his crew run the show in Memphis, you feel as though you're watching a sting operation in action. And you wonder how the customers believe a single word they're hearing.

But the meat of the movie is Bennett the man, a gravelly voiced hustler who's as hyper as a speed freak. No amount of beer seems to slow him down. As he puts it, "Even when I'm sittin' still, I'm still . . . movin'." As his loyal assistant puts it, "You need a . . . Xanax the size of a grapefruit." When we first meet Bennett, he's leading a cozy home life with his wife and two daughters. But the minute he leaves for Memphis, he morphs into a crazed performer who treats each job as if it's his last. "This is a show to me," he says about the gig. "It's not a sale." The car dealer is paying him about $12,000 to put the sale together, so the pressure is on him to move enough cars to justify his presence.

Toward the end of the movie, as the sale weekend wraps, exhaustion creeps into Bennett's voice, and you feel his tragic longing to be what he calls "normal." He knows that while the manic slasher life sucks him dry and leaves him hollow, he'd be miserable doing anything else. It's a sad paradox, the compulsion of a salesman, but not as sad as the less fortunate people of Memphis -- the bankruptcy capital of the world, we're told -- who blow their money on questionable cars. The movie's Stax soul soundtrack is easy to listen to, but those images are hard to watch.

Matthew Gilbert can be reached at gilbert@globe.com.