We begin in the perspective of a judge. A woman, Simin (Leila Hatami), and her husband, Nader (Peyman Maadi), sit uneasily side by side, explaining directly to the camera the reasons she is seeking a divorce and he is opposing it.

Simin wants to leave Tehran with their preteen daughter for a life of greater opportunity in the West. Nader insists on remaining because he is his senile father's only caretaker. Each has a clear, logical position and each is fuming for having to defend such a plainly true idea. Simin coldly declares that because the old man has Alzheimer's, "he doesn't even know that you're his son. What difference does it make?" Nader angrily spurts, "But I know he is my father!"

So far, so intriguing. Every good divorce drama must dissect the warring duo's personalities. But the Oscar-nominated Iranian film "A Separation" is no mere chamber drama of an embittered couple wielding emotional truncheons. After the courthouse opening, writer/director Asghar Farhadi's clear-eyed film follows Simin and Nader through a cascade of misunderstandings, leading to grief beyond their reckoning. "A Separation" steadily expands its focus, introducing new characters thinking in different vocabularies, weighing different agendas, all affected by the falling dominoes the divorce sets in motion. The result is a suspenseful, fascinating, vexing moral thriller.

Office worker Nader can't stay home to tend to his father, so he hastily hires a fundamentalist Muslim woman, Razieh (Sareh Bayat), as attendant. To the secular Nader, it's a straightforward matter, but Razieh faces a maze of theological issues while looking after a man who can't use the toilet or bathe by himself. When the inevitable happens, she calls a religious counseling hot line, asking, "If I change him, will it count as a sin?

While Razieh is devout, humble and well meaning, she's not above keeping important secrets from her employer and her husband, a hotheaded religious hardliner. Nader soon finds Razieh negligent, which leads to a squabble over payment, which leads to disastrous collateral damage, and courtroom proceedings far more serious than divorce.

The film is stunningly acted, emotionally universal and culturally specific in ways that make it all the more engrossing. There's a white-hot intensity to the Iranian court scenes, where the parties assert their grievances and rebuttals without the lawyerly rigmarole of Western trials. The judge guides the proceedings by asking questions that cut to the heart of the matter, and the film does, too.

Telling a story in which no one is without guilt, "A Separation" moves beyond one couple's sundering marriage to reveal growing rifts between generations, ideologies, religious mind-sets, genders and classes in contemporary Iran. As for who is right judicially or morally, see it with a group of friends and prepare yourself for a long debate.