It starts during morning rush hour in New York City, when Wall Street lawyer Gavin Banek (Ben Affleck) and insurance agent Doyle Gipson (Samuel L. Jackson) have a minor traffic accident. After each man assures that the other is uninjured, Doyle tries to exchange insurance information, but Gavin, who is due in court, tries to speed things up by offering a blank check instead. When Doyle, a recovering alcoholic determined to do things by the book, refuses the offer, Gavin decides to split. Doyle asks for a ride, but Gavin speeds away, shouting "Better luck next time" as he leaves the man standing by a car with a flat tire.

Although neither man knows it, they are both headed for the same building. And what Gavin doesn't realize is that, in his haste, he left a very important folder behind with the man he just screwed.

The ramifications of the fender-bender are quickly felt. Gavin shows up in front of a judge minus the only papers that will back up his company's claim to the estate of a multi-millionaire. He tries to bluff his way out, but only succeeds in putting himself in legal jeopardy. Meanwhile, Doyle arrives 20 minutes late for a custody hearing and, as a result, must listen as the judge grants his estranged wife permission to move to the other side of the country with his two boys.

Both men are devastated and react in anger. After a phone exchange between the two dissolves into shouting, Gavin strikes first, getting the name of a man who "fixes things" from Michelle (Toni Collette), a co-worker and former mistress. After hacking vital information about Doyle and preparing to ruin his finances with one keystroke, the fixer (Dylan Baker) turns to Gavin and says, "Is there any other way?" When Gavin wonders if any other option exists, he is told, "Sure. Just call him up and be nice to him." Barely missing a beat, Gavin fixes his eyes on the keyboard and says, "Do it."

And so the war begins.

What makes the film so fascinating is that the only way either man can triumph is to recognize his destructive behavior, take responsibility for his actions and begin to act reasonably. As the retaliatory strikes escalate, you begin to wonder if either Gavin or Doyle is capable of such an epiphany.

Working from a screenplay by Chap Taylor and Michael Tolkin, director Roger Michell slowly, steadily ratchets up the tension level. Instead of using the traditional whack-you-over-the-head approach, he employs subtle sound cues and refreshing washes of subdued natural lighting. Along the way, more and more is revealed about the character of each man.

Gavin has been so busy pursuing the next brass ring that he never gave a second thought to ethics. When reminded by his cynical wife (Amanda Peet) that lawyers at his station spend virtually all their time looking for ways to cheat, he seems genuinely surprised. Doyle is also lost, believing that abstinence from drinking equals recovery. At one point, his frustrated AA sponsor (William Hurt) shouts that his addiction is not to alcohol, but to chaos.

None of this could work without exceptional acting and every performance in "Changing Lanes" is top notch. Samuel L. Jackson, a master of expressing rage, balances the explosive nature of his character with welcome nuance. He hits all the right notes here. Ben Affleck is just as good. After appearing in so many comedies and big budget popcorn flicks, it's easy to forget just how talented an actor he is, but he offers a fine reminder with a wonderfully measured turn as the desperate attorney.

William Hurt makes the most of his brief time onscreen, exhibiting none of the glibness that periodically taints his work. Playing Doyle's estranged wife, Kim Staunton adroitly shades her character, making her more than just another wronged woman. As Gavin's ex-girlfriend and current wife respectively, Toni Collette and Amanda Peet are equally impressive. To no surprise, Dylan Baker is excellent, and check out Sydney Pollack as Gavin's boss - his creates the consummate corporate shark without ever getting cartoonish.

At times, "Changing Lanes" pushes the edges of credibility. Gavin's blank check approach to the car wreck, while obviously necessary to propel the story, still seems an odd thing for a lawyer to do. As for the law firm that employs him, security seems to be nonexistent at several key plot points. Finally, without giving anything away, the wrap-up of the story is a bit too pat for my tastes. Regardless, "Changing Lanes" is superior fare. Hopefully, it will draw the audience it deserves.