The corners and sidewalks at truck rental places, hardware stores, building supply stores in Marin County are filled with small, brown skinned men, in day wear shirts, baseball caps, sturdy pants and athletic shoes. They are out early and stay most of the day, day after day. They number in the hundreds, signaling passing motorists and especially drivers of pick-ups, and SUVs. If you have work, they can do it: dig a ditch, load a truck, sweep a construction site, set up chairs for a big event. Pay them a handful of cash and they are gone. Your work is done. Everyone is happy — like magic elves that appear and disappear at the clap of the hands. Farmers have know about these elves for decades. Harvest time: poof! Appear. Harvest over: poof! Disappear. And most people like it that way. It’s the closest thing to the free market ideal of supply and demand for labor that can be achieved. No annoying residents who, out of work, need social support. These migrants move on, move on.

Of course it isn’t magic that they appear. Of course they are not elves who poof in and poof out of the great workshops of the world. Like all of us they eat, drink, excrete, love, hate, ache, despair, laugh, hope. Unlike us they come from some of the poorest places in the world. Places where it takes an entire family working 10-12 hours a day to eat, where dozens crowd in single shantys, where bathing is a once a week luxury. Unlike us, with us on their borders, they will risk life and limb on long, fear fraught journeys to find a refuge in a strange land where their waking hours of work gives some greater promise of escape than staying at home.

Sin Nombre, a Sundance debuted film by newcomer Cary Fukunaga from Oakland, California is about two small subsets of this south-of-the-US world, and the long desperate journey to “La Norte,” mostly on the tops of north-bound trains, unprotected from the weather or human predators. One group of 3 is Sayra (Paulina Gaitan) traveling with her long absent father and his younger brother, destination New Jersey where her father’s wife and other daughters live. The other group, begun as three but quickly reduced to one, with a murderous gang on his trail is Willy, or El Casper (Edgar Flores). He, along the leader of the local Mara Salvatucha gang and a young recruit, after a fearsome introduction to their lives and values, hop the train to prey on the north bound workers. Sayra attaches herself to Willy after he saves her from being raped by the leader and the story progresses as the two head north, both hoping for new lives. Having killed his gang leader Casper is in deadly danger for the rest of the trip, the film braiding the dangers to the migrants of hunger, weather, physical danger with the violence of the gang, to each other, and the migrants themselves. A third strand is the recruitment and indoctrination of the 12 year old boy, “Smiley”, into the gang.

Fukunaga has done an unbelievable job of taking us into the lives of the desperate migrants and viciously desperate gang members. The lighting, the camera choices, especially some night shots in the train yard are first class. The impression of the full-face tattoos, scars, casual violence and mix of Christian symbology with tenderness and brutality of the gang members will stay with you a long time. How Fukunaga got his cameras onto the tops of freight trains and into train-side squatter camps is a feat in itself, much less the panoramic shots of sunsets, the moving shots of rail side slums, of people tossing oranges, or stones, at the riders. Nor is this made up from a romanticized past, as of North American hobos of the depression.

Yet somehow the film falls short. The three strands, of migrant danger, gang violence and bringing the young boy into the gang, don’t leave equal impressions. Instead of a story of dangers to migrants, prey to the gangs being one of them, we have story of gang savagery, doubled by its corruption of the young boy, with a side story of migration to the north. The result to the viewer is less of understanding and compassion for the migrants — who most of us see, and take for granted, daily– and more fear and disgust at the gangs.

In part, it seems to me, the two of the three stories don’t mutually re-enforce each other, because there is a certain schematicization in the telling. The gang somehow tracks the fleeing Casper, who we see for days on the trains. Border to border in Mexico is about 800 miles, on very slow trains. Yet we never see the gang covering the same distance, in cars, on other trains, on the same train. They just appear at the next stop, and not other members of the widely extended Mara Salvatrucha gang, but the same thugs, from the same city of origin. The tension of knowing they are after Casper is not reinforced with cars racing trains, multiple phone calls, all the devices of modern chase movies. Though the film flashes up the names of cities as the train and its passengers go through, and though Sarya’s father brings out a map of the distance they have to travel, we don’t know well enough how far they’ve traveled, for how many days, and therefore, how close to success or failure they are, or, until the final frames, that the revenging gang members follow Sarya and Casper right to the banks of the Rio Grande.

To a lesser degree, but similarly, we don’t see the details of how the migrants are getting the food to feed themselves, how they relieve themselves; we don’t see quite enough of their pure misery. We know they are poor and desperate but we don’t have enough details to outweigh our visceral response to the gang presence with a sense of the entirety of their plight. It’s as if Fukunaga let the more obviously shocking images overwhelm the actually more shocking story of the migrant experience, of which being preyed upon by tattooed hoodlums is only a part. Finally, there is a collapsing of the different peoples and cultures who are making this migratory run into one, more or less homogeneous group of brown Spanish speakers. We don’t get a sense that the Hondurans are different from Guatemalans –and therefore wary of each other–, different from the Mexicans of Chiapas, different from the Mexicans of Tamaulipas. We don’t know if the Salvatruchenos are Mexicans, immigrant Salvadorans– where the gang originates– or what. Without differentiation, they all are collapsed into the searing images of the gangs — vicious, brown skinned, Spanish speaking thugs. Be afraid.

The story of the young boy’s recruitment and indoctrination into the gang is well integrated into the gang story. We believe it. And yet we are in disbelief. A twelve year old being shown how to shoot a man in the head, arms around him to steady his hand, as casually as being shown how to swing a bat at a baseball.

For all that, it’s a film worth seeing, perhaps along with the 1983, and very interesting, “El Norte,” by Gregory Nava, which tracks a similar journey north, with a happier ending.