Just when you thought Sean Penn had the Best Actor Oscar locked up for his career high in Mystic River, along comes tough competition: himself. In this scorcher of a drama from Mexican director Alejandro Gonzalez Inarritu -- it's only his second film, after the brilliant Amores Perros, and his first in English -- Penn burns with ferocity and feeling as Paul, a math professor faced with the possibility of death after a heart transplant. His wife (Charlotte Gainsbourg) wants to have a baby, something of him left behind. Paul sees spirituality in terms of numbers, the twenty-one grams (the weight of a hummingbird, a chocolate bar or a stack of five nickels) that leave our bodies at death.