As the story begins, a tortured heart-transplant patient (Sean Penn) wonders, "What am I doing in this pre-corpse club?" as his wife (Charlotte Gainsbourg) implores a gynecologist to use her dying husband's sperm for artificial insemination. Across town, a conscience-stricken Born Again ex-con (Benicio Del Toro) interrupts a birthday celebration with a horrific tale to tell his long-suffering wife (Melissa Leo). And a hysterical drug-addicted party girl-turned-suburban housewife/mother (Naomi Watts) faces the devastating loss of her husband and two daughters.

At first, writer Guillermo Arriaga's complex construction is confusing - like the non-linear structure of "Memento" - but soon the seemingly random past-and-present fragments seamlessly interlock with a cohesive texture, like pieces in a jigsaw puzzle. Indeed, the lives of the disparate characters are intertwined in riveting and ironic ways. At the emotional center, grieving Naomi Watts ("Mulholland Drive") exudes a ferocious, relentless intensity that deserves an Oscar nomination, while Sean Penn ("Mystic River") delivers an astonishing, electrifying performance which won him the Best Actor award at the Venice Film Festival. On the Granger Movie Gauge of 1 to 10, "21 Grams" is a powerfully provocative, weighty 8. "Life goes on" - all the devastated people whose lives have been affected by the automobile accident are told - but at what price?