Written by Guillermo Arriaga, who also wrote Inarritu's Amores Perros, 21 Grams is the story of three individuals, sinners all, whose lives intertwine through tragedy and dereliction. Paul Rivers (Sean Penn) is a math professor suffering from advanced heart disease. His wife, Mary (Charlotte Gainsbourg), is so devoted to him she wants to get pregnant even though Paul may not live to meet his child. But Paul has been repeatedly unfaithful to Mary, and he doesn't begin to appreciate her love. He's also self-destructive, continuing to smoke even though he's waiting for a heart transplant.
Cristina Peck (Naomi Watts) is a former coke-sniffing party girl who has cleaned herself up, settled down with a prosperous architect and raised two little girls to whom she is obviously devoted.
Jack Jordan (Benicio Del Toro) has two children and a sordid past too. He's been a boozer and brawler, and he's been busted for robbery and battery. But he's been straight for the past two years. Nurtured by a fundamentalist preacher (Eddie Marsan) who ministers to the poor and the violent, Jack has devoted himself to being a good father and a loyal husband to his wife, Marianne (Melissa Leo). Marianne is not a believer, but she embraces the religious life as long as it helps Jack.
Following a strategy even more extreme than the one they employed in the three stories in Amores Perros, Inarritu and Arriaga deliver their story as a chronologically fractured collage. At the beginning of the film we see scenes from near the end, and throughout, the narrative moves forward and backward in time to find its characters in various degrees of contentment and anguish.
The hook is not what happens. Though we eventually discover that Paul and Cristina are initially strangers with no connection whatsoever, the picture's very first scene shows Paul and Cristina in bed together, and a passage not long afterwards shows Jack driving a gun-shot Paul to the hospital while a desperate Cristina declares her love for Paul and tries to staunch his wound. So from the outset we know most of what happens. And gradually we come to understand how and why. But we even have command of both of these two elements by mid-picture. Jack accidentally kills Cristina's husband, Michael (Danny Huston), and her two daughters in a traffic accident. Afterwards, Michael's heart is transplanted into Paul's body. And Paul, saved in a way he doesn't deserve and doesn't honor (he never stops smoking), hires a private detective to learn the identity of his donor. The P.I. leads him to Cristina.
I presume the filmmakers had reasons for what they decided to reveal when, but I will concede defeat in ever detecting a pattern to the way the film has been put together. This decision to tell the story in flashbacks and flashes forward has an intriguing aspect for a long while. Because we are often uncertain where we are in time, we stay more alert. Because we know where the story is heading, we examine each passage for clues to how we're going to get there. Near the end, however, as we sort the jumble of scenes into a coherent narrative, the jigsaw strategy starts to feel gimmicky. We yearn for a payoff that never quite arrives.
Still, the fractured chronology of the picture is a way for the filmmakers to wonder about predestination and grace, to puzzle over God's hand in the events of our lives. In trying to save himself, Jack has surrendered himself to a belief in God's absolute control over his life. When he wins a truck in a raffle, he believes that the vehicle is a gift from Jesus Christ himself. But then what does he do when it's that pick-up he's driving when he runs over Michael Peck and his children?
This is a core dilemma of religious faith. We try to believe in a God who is at once all-caring, all-knowing and all-powerful, and those three ideas can't be held together in the human mind at once. In the end, Inarritu and Arriaga surrender to the principle that we won't ever get it figured out in this life. In Philippians 1:21, the Apostle Paul says, "to live is Christ and to die is gain." Paul Rivers meditates on the loss of 21 grams and wonders what is gained. At the end of the picture, two characters sacrifice themselves for others. The filmmakers don't assert that this transforms or even redeems either one. But perhaps it does. And that, perhaps, is all we have.