21 Grams is extremely complex, following three different story lines as they intersect and become one. Director Alejandro Gonzalez Iñárritu jumps in between the three stories, as well as many different time zones, to tell you what is happening, what has already happened, and what is going to happen - all at once. This is very confusing for the first half of the film because you really don't get a good idea of what is going on, but it all comes together in the second half.
Normally, I offer a fairly detailed synopsis of the plot of a film in my reviews, however it’s impossible for this film without including major spoilers. All I can give you is a brief summary of the characters involved.
Naomi Watts' performance as Cristina really shone through and impressed me. Cristina is a grieving mother who recently lost her husband and two daughters, and is turning to drugs and alcohol in order to cope with her pain.
Paul (Sean Penn) is a terminally ill mathematician who is married to a woman he doesn't love. She wants to have his child while he waits for a heart donation and tries to deal with the concept of what's going to happen when the time comes and he actually dies.
Jack (Benicio Del Toro) is an ex-con who has been in and out of prison since he was 16-years-old for everything from drugs to grand theft auto. Jack has turned his life over to the Lord and is clean of drugs and alcohol. He tries to keep his life in order and raise his family.
A freak accident resulting in tragedy brings these three people and their problems together.
You have to pay extra close attention to this film. If your mind wanders at all you will get lost and quite possibly never find your way back. The way the times move around will get you wondering if Alejandro just shuffled the scenes together and threw them in. I am being facetious, of course, as it becomes obvious about an hour into the film that Alejandro knew exactly what he was doing and he knew exactly where he wanted every scene to be.