'Grams' is worth its weight in gold

"21 Grams" confirms the promise shown by Mexican filmmaker Alejandro González Iñárritu in his 2000 debut, the Oscar-nominated "Amores Perros."

Here again are the intricate plot structure, the heartfelt acting from an expertly chosen cast - Sean Penn, Naomi Watts, Benicio Del Toro, Clea DuVall - and the restless, adventurous camera work.

This time the story is more streamlined. Yet it's clear Mr. Iñárritu hasn't changed his essential idea that human experience is too rich to be crammed into a linear narrative. "21 Grams" leaps back and forth through time and space in complex patterns that mirror the emotional and physical complexities of the lives he's exploring.

As in "Amores Perros," it's a car accident that sets the action going. And it's the life-or-death nature of the events sparked by this mishap that explains the new movie's title, referring to the amount of weight a body supposedly loses when its soul leaves the material world.

Iñárritu doesn't take this notion too literally, using it as a metaphor for the limitations of our ability to understand the enigmas of our own lives and those of the people we interact with most intimately.

Penn plays a math professor who's been diagnosed with a terminal illness, but may survive if he can receive a heart transplant. Meanwhile his wife (Charlotte Gainsbourg) hopes to become pregnant so a part of him will live on if he dies.

In a very different milieu, Del Toro plays a former thug who now puts his overflowing energy into evangelical Christianity, while his wife (Melissa Leo) wishes he'd show the same commitment to his family. A third story line centers on two sisters (Watts, DuVall) coping with challenges rooted in the past.

With its fragmented timeline and frequent shifts in tone, "21 Grams" is vastly more challenging than any Hollywood picture this year. It's obviously not destined to be a big financial hit, but audiences should respond to its meaningful issues and superb performances.

At the very least, look for it on 10-best lists next month, and there's every chance it will be a strong contender at the Oscars. Filmmaking so sensitive and intelligent deserves its weight in honors.

• Rated R; contains sex and violence.