Mike Nichols's "Closer," based on the acerbic 1997 play by Patrick Marber, brings the battle of the sexes into the brave new world of cybersex. One pair of the story's heterosexual London quartet--a dermatologist named Larry (Clive Owen) and the divorced photographer Anna (Julia Roberts) meet because Larry thinks she has summoned him to a rendezvous after a salacious chat. In fact, Larry was chatting with Dan (Jude Law), an obituary writer and failed novelist posing online as Anna, whom he lusts after even though he's living with the waifish waitress/stripper Alice (Natalie Portman). This is but the first of the dirty tricks the men play on each other in this nastily funny erotic roundelay. As the four ardent, duplicitous characters keep changing partners, it becomes clear that when push comes to shove, male competitiveness trumps romantic desire. Dan and Larry are straight, but they're more obsessed with f---ing with each other's minds than f---ing the women they think they love.

Nichols has traversed this territory before, in his film of Edward Albee's "Who's Afraid of Virginia Woolf?" and in his coolly savage "Carnal Knowledge." Marber's play has been highly acclaimed, but it's not in the same league with those movies: his characters seem more like puppets on the author's string than actual people, and his insights into sexual gamesmanship are hardly new. Yet with a cast this good, and a director this knowing, "Closer" has many moments of mordant power. Portman, as the most open and vulnerable of the quartet--this is her first real adult role--is truly poignant. And Roberts shows us some new colors: she's a depressive seductress, both a schemer and a victim of her own careless passions. But it's the charming, loutish men--Law and Owen--whose sins are the darkest and who shine the most brightly in this chilly, caustic, foul-mouthed anatomy of modern romance.