How much does life weigh?

A freak accident brings together a terminally ill mathematician (Penn), a grieving mother (Watts) and a born-again ex-con (Del Toro) in Alejandro Gonzalez Inarritu's fantastic multi-layered follow up to his debut 'Amores Perros', a gripping story that takes them to the heights of passion, the depths of obsession and sees the promise of revenge...