21 Grams is a film heavy on atmosphere and dark, brooding characters, but light on any of the profound purpose that it wants so desperately to convey. Director Alejandro Iñárritu and screenwriter Guillermo Arriaga, are earnest in their attempts to sink some larger meaning into this gloomy film, but what surfaces is never more than unhopeful and ponderous.

The film’s lofty goals are muddled in its title which refers to the weight that leaves the human body when it dies. Twin voiceovers by Sean Penn’s character Paul, in the beginning and end of the film, suggest that this number may be tied the mass of the human soul or at least a stack of five nickels and that’s the film’s major problem. It never commits to anything but a vague philosophy about the human condition. The films insistence on this fuzzy and ethereal idea seems misdirected considering that a much stronger metaphor lies not in questioning the weight of the soul, but in questioning the weight of a human heart which in the case of the film's three main characters has been stripped of every ounce of morality and faith. Of course “10 ounces (on average)” would have made for an awkward title.

The storyline is intricately conceived and centers on the fractured lives of three people: Paul Rivers (Sean Penn), a mathematics professor dying of what else but -- heart disease, Cristina Peck (Naomi Watts) a loving mother whose life is shattered when her two daughters and husband are run down by struggling ex-con turned youth minister, Jack Jordan (Benicio Del Toro). Most of the films exposition is revealed through a series of jarring out of sequence scenes in which we see the characters future past and present in seemingly random order. The reward for piecing together the jumbled narrative is a brutal revenge story that eventually catches up on itself to find Christina recruiting Paul (who has been saved by a heart donation from her husband) to murder Jack in a grimy hotel room. This time shifting story structure is hardly innovative and seems to be an obvious way to tell this grim and slowly paced tale. Audiences will be glad that they were spared being dragged on an agonizing linear journey with such tormented souls. It gives us something to do while we try and figure out why we should care.

Penn’s performance as Paul is enthralling and detailed. He maintains his reputation as one of America’s finest actors. His work here makes extraordinary use of his uncanny ability to shape a characters emotional state with the smallest of gestures. When Paul is asked why it is so important that he track down the history of his hearts original owner he responds quietly, “because I need to know who I am now”. In the hands of a less skilled actor this line might be overwrought with thematic importance. Instead Penn delivers it with just enough hue to stand out as one of the few resonant moments in the film. Del Toro is also fascinating as Jack, a character hemmed in by his criminal past and seeking redemption where ever it is offered. Del Toro is always an intense presence and this performance is no exception. He approaches the role with a just under the surface restraint that is equally as nuanced and powerful as Penn’s performance. Jack is a tragic underdog crushed beneath the weight of circumstance and under Del Toro’s care he provides the only real source of empathy for the audience. The only bump in the otherwise solid acting is Naomi Watts who approaches Christina with generic, grief-stricken widow exaggeration. She is content to scream her way to an Oscar nomination and given the academies penchant for these types of female roles, I am sure that her shrieks will be rewarded. What’s missing from her performance is the depth of feeling found in the characters quieter scenes. Watts’ strokes are broad, loud and predictable. During more pensive moments she seems uninvolved as if she can’t wait to get to the juicier stuff. Her impatience is distracting.

It is clear that great care has gone into telling the story through action and the dialog is sparse, but carefully crafted. The problem with 21 grams lies in its own self imposed grandeur. The dreary cinematography, reminiscent of Steven Soderbergh’s Traffic, combined with Iñárritu’s head in hands, staring off screen compositions have the film dangling in the waters of over-stylized pretension. Iñárritu’s is clearly interested in the dark violent nature of the human soul and in 21 Grams he wants to tackle themes of redemption, cruelty and cosmic coincidence, all ideas that are dealt with to much better effect in his Spanish language film, Amores Perros which was also written by Guillermo Arria. Unlike that film which benefited from being set in the seedy underworld of Mexican dog fighting, Iñárritu must explore characters with more ordinary and accessible lives and because he has chosen such extreme presentations of their psychological collapse we never relate to any of their self destructive choices. Iñárritu wants us to believe that these characters have been thrown together by some cosmic convergence, but they are such severe examples of emotional disintegration that their meeting seems inevitable rather than mystical. Who else on this planet could they relate to, but themselves?

Iñárritu never lets us catch our breath long enough to think about the questions he asks and never seems satisfied with the amount of anguish and misery he piles on. As for pondering the source of that mysterious weight that leaves the body upon death, one has to wonder if Iñárritu was saving this obscure tidbit for the right film. It seems irrelevant here and thrown in to add some consequence for the art house crowd to discuss over their green tea chai. It is too bad that he could not trust the taut script and the fine cast to tell this story. He tinkers with this hotrod until the engine stops running and in the end we are left with something nice to look at, but it gets us nowhere.