Brad Pitt plays a scatterbrained, indentured mob lackey on a do-or-die delivery assignment. Julia Roberts plays his neurotic, therapy-addicted girlfriend who made him promise he'd get out of the rackets. James Gandolfini is a hypersensitive crybaby hit man who kidnaps Julia to make sure Brad doesn't get any bright ideas about selling the antique pistol he's sent to fetch from south of the border.

This winning talent combo and a very droll, quite original script make "The Mexican" the first sublime cinematic bonbon of 2001 -- a consistently chuckle-packed caper comedy with charm and repartee to spare.

Directed by Gore Verbinski ("Mouse Hunt"), who effortlessly navigates several blindsiding but fine-tuned plot twists, "The Mexican" features Pitt as Jerry, a hapless, handsome perpetual screw-up who has been doing odd jobs for a mafioso to atone for causing a traffic accident -- an accident that inadvertently landed the kingpin in the clink (there was a body in his trunk at the time).

Jerry's been told several times he'd be off the hook after one more assignment, and when his fiancée Samantha (Roberts) hears he's being sent to Mexico on this bizarre charge to take delivery on a cursed 19th Century handgun, she's had enough. She throws his stuff out of their apartment window along with a lunatic stream of couples' therapy mumbo jumbo.

With flabbergasted Jerry shrugging his shoulders and off to Mexico, Samantha heads for Las Vegas on what was supposed to be a romantic holiday for two. But it seems that gun Jerry is after is a hot property, and before she even makes it out of L.A., she's kidnapped by a bruiser named Leroy (Gandolfini) as an insurance policy against Jerry getting any wise ideas about selling the pistol elsewhere.

Pitt is surprisingly adept at portraying a knucklehead without forsaking an ounce of his charismatic hunk appeal. He subtly plays to the circumstances of his comedic scenes, rather than clowning for the camera, as Jerry Keystone-Kops his way through spades of bad luck trying to keep the gun from other interested parties (it changes hands half a dozen times) and remains largely oblivious to the fact that his sweetie is in the hands of a notorious psychopath.

Meanwhile, Roberts packs her role with the same kind of frazzled femininity that made her so endearing in "My Best Friend's Wedding." Samantha somehow hits Leroy's soft spot while compulsively unloading all her relationship baggage on him as he drives her at gunpoint through the desert, and soon they're bonding like girlfriends. Leroy, it turns out, is a gay psychopathic hit man -- which has contributed to him being unlucky in love, as well. And he's pretty blue about it.

With dozens of such whimsically off-the-wall elements, "The Mexican" could have gone wrong -- really wrong. But there's so much talent here the film's only significant problem is that it packs one too many twists into a badly paced last act.

The screenplay (by actor-screenwriter J.H. Wyman) has a flawlessly executed story arc that includes dexterous, enchanted asides about the origins of the gun and has just the right number of narrative curveballs. Verbinski's outwardly effortless (but in fact, quite premeditated) direction gives the film an enjoyably jaunty atmosphere. And the two leads each give the kind of personality-packed performances that earned them their stardom.

As a couple, Pitt and Roberts have classic cinema comedy chemistry. But they spend most of the movie apart. His blundering Murphy's Law scenes in Mexico provide "The Mexican" its spirit. Her scenes with the hit man -- collectively about half the movie -- give it its soul.

But ultimately it's Gandolfini who steals the show, bringing 100 percent of his mafia credibility with him from "The Sopranos" but dousing it with a laughably gushy-yet-sympathetic vulnerability.