ATLANTA - Somebody's got a nasty mouth.

The compelling, unsettling and finely acted "Closer," based on Patrick Marber's popular, incendiary play of sex, relationships and lethal adultery (is there really any other kind?), dives deep into the vernacular of the physical act of love.

Julia Roberts speaks the kind of graphic sexual detail you'd never expect to come out of her sweet, "Pretty Woman" mouth. Same for all-grown-up Natalie Portman, who it seems as though just last week was playing all cute and nice as her royal shyness Padme in the latest "Star Wars" film.

Everybody in "Closer" talks filth. Or types it.

Jude Law and Clive Owen have an often funny but certifiably steamy Internet chat room pas de deux (Law's character is playing a prank, acting like he's a frisky she) that could singe a moviegoer's thought process.

The point - and it's not entirely clear whether "Closer" has a definitive one - may be that sex makes for interesting relationships. The stuff of attraction is illusive, the battle for dominance is quite vicious and much of the world is comprised of the walking wounded.

What's crystal clear is that "Closer" has a few riveting scenes and actors capable of grabbing viewers by their throats. Seriously, Roberts hasn't been this good since "Erin Brockovich." Owen and Portman are probably Oscar shoo-ins for supporting nominations.

Law plays a newspaper obit writer in London. He meets Portman, an apparent waif and, later, a sure-fire stripper. After they've been a couple for a while, they meet Roberts, a photographer. She meets Owen, a dermatologist. Then he meets Portman. But long ago we were already off to the races.

Their sexual politics is like Watergate - all break-ins, slush funds and dirty tricks.

As a stage play in London and New York, "Closer" became the modern-day "Who's Afraid of Virginia Woolf?" Or, more accurately, "Carnal Knowledge," where Jack Nicholson surfed a sex game till his own chutzpah ate him alive.

On film, "Closer" works only in fits and starts. The play has been transferred almost completely intact, but film exposes its flaws. A penultimate scene with Law and Portman is written too pat to deliver its intended firepower. The film's crux - an adulterous entanglement between Law and Roberts - doesn't have much, if any, sexual heat.

Those questionable moments are easily made up for with a sizzling strip-club encounter between Owen and Portman, and an even better at-home duel between Owen and Roberts. The latter is biting, hard, cruel and likely one of the strongest and truest break-up scenes captured on film. By scene's end, each character's nerves lay exposed, their souls frazzled.

This is director Mike Nichols' best theatrical effort in years. (Anybody even want to remember "What Planet Are You From?" I didn't think so.) He spares us hotshot camera work, concentrating on the actors and freeing them to deliver their intense dialogue.

With TV's Emmy-hogging "Angels in America" and now "Closer," Nichols seems to be regaining the stature he attained with films like "Silkwood," "Carnal Knowledge," "The Graduate" and "Virginia Woolf."

And like that last society-burner, "Closer" tests the public's patience with vulgarity.

It's risky, edgy stuff. With one nasty mouth. Make that four nasty mouths.

TITLE: "Closer"DIRECTOR: Mike NicholsCAST: Julia Roberts, Jude Law, Natalie Portman, and Clive OwenRATED: R for sequences of graphic sexual dialogue, nudity/sexuality and languageGRADE: * * * ½ (on a scale of 5)