A sexually charged drama of cross-pollinating infidelity from director Mike Nichols -- whose best work has always tapped into such raw and sensitive areas of the human psyche -- "Closer" derives all its fascination from the nitty-gritty, down-and-dirty character nuances brought to life with discomforting veracity by its foursome of fine actors.

Julia Roberts (as Anna, an aloof but respected photographer), Clive Owen (as Larry, a smarmy doctor), Jude Law (as Dan, an obituary writer and failed novelist) and Natalie Portman (as Alice, a punkette-lite stripper who blows with the wind) are all strangers as the film opens in modern-day London. But as the story leaps forward to pivotal episodes over several years, a series of dates, marriages, illicit liaisons, break-ups and jealous traps shape their boomeranging romantic lives.

The cunning direction of Nichols ("The Graduate," "Carnal Knowledge," "Who's Afraid of Virginia Woolf") viscerally plugs into the emotional voltage of these edgy, passionate, dishonest, desperate, sometimes sweet but often brutally frank relationships in almost every scene. But the film begins deceptively like a romantic comedy as Dan charms the alluringly unfettered Alice on her first day in London, coming to her aid when she's hit by a taxi. "Please remember our traffic tends to come from the right," he glints with all this English panache after realizing her injuries aren't life-threatening.

Almost immediately, however, "Closer" pounces forward in time to the day Anna is taking Dan's picture for the jacket of his first novel -- inspired by Alice's troubled but tenacious life. When he makes a pass at the photographer while Alice waits outside, the move reveals, with an intricacy only a truly versatile actor could achieve, where his relationship with his muse now stands.

But this scene is one of several false moments that feel like hurdles for the actors, albeit hurdles they continually overcome. The acrimonious flirtation between Law and Roberts lacks credibility, yet it begets a gut-wrenching scene between the two women as Portman's savvy but vulnerable character catches on instantly to the infidelity afoot.

Another hard-to-swallow incident finds Dan posing as a woman on an internet sex-chat site, luring Larry (surfing from his hospital office in an unlikely scene accompanied by incongruous swells of classical music) to a false date, where he then meets Anna for the first time. This chance encounter leads to something between them that may not be love, but it sets in motion all the heart-wrecking to follow.

A bigger problem with the story is that these men are both such base creatures -- single-minded, quick to become smitten, enraged, forlorn and vengeful (especially toward each other) -- that by comparison the film seems to have neglected the female characters. Writer Patrick Marber (adapting his own stage play) fails to tap into whatever has made these women incapable of recognizing relationship red flags when they see them.

But as the title implies, the closer "Closer" gets to all four people, the more absorbing their internal (and intermingling) turmoil becomes -- and that's where the film's casting pays off. Roberts, Portman, Law and Owen ("King Arthur," "The Bourne Identity") are not afraid of the darkness and damage in their characters' hearts. They're don't shy away from appearing unsympathetic, and Nichols nurtures the intimacy and immediacy this fearlessness brings about.

The result is a film saved from its implausible emotional overtures by its unvarnished emotional minutiae.

The picture's best asset, however, is Portman, who is beginning to come into her own as a major talent. In her hands, young Alice's flirting, knowing eyes are windows to the most complex, self-aware and psychologically plucky soul of the bunch.

There has been much chin-wagging about the fact that, at the actress's urging, Nichols removed a manipulative striptease she'd shot for a scene in which Larry, shattered by a discovery of infidelity, visits Alice in a nudie bar. That this scene feels all the more invasive for what it doesn't show speaks volumes to her ability to be naked in more fascinating ways just through her acting.