Sin nombre (15)

This immigrant tale is a flimsy but entertaining gangland thriller

The Mexican film Sin nombre is an immigrant story with elements of gangland thriller, western, road movie and the sort of socially conscious exposé of street life that might look pretty (City of God) or feel true (Pixote), but can rarely do both. Sin nombre plumps for pretty. It's entertaining enough, even as you feel the tale's untapped complexities behind the diluted version served up here.

Mexico gives good location, from the garland-festooned cemeteries of Tapachula, where tattooed thugs congregate, to the hobo romance of the railroads snaking northwards. Not that romance has much room to thrive there. Sayra (Paulina Gaitan) is one of the bedraggled hopefuls crowded on to the roof of a freight train bound for the Mexican-North American border. On the journey, she meets young Casper (Edgar Flores) in circumstances best described as unpromising - he is part of a gang attempting to rob her at gunpoint, then Casper has an attack of conscience and starts swinging his machete around, and soon Sayra owes him her life. Back in the day, that would have made a lovely story on Simon Bates's Our Tune slot.

Unfortunately for Casper, his chivalry lands him with a death sentence from his former homies. We already know that his gang, the Mara Salvatrucha, is an unforgiving bunch. In their neighbourhood, life is cheap and underwear is visible. Their initiation rites involve prospective members being beaten, kicked and stamped on in scenes of brutality previously glimpsed only during half-price day at World of Leather. If that's how they treat people they like, imagine what they do to their enemies. Actually, you don't need to imagine: it's all here. Let's just say you'll never look at Pedigree Chum the same way again.

It's hard luck for the more contemplative parts of Sin nombre that the gang scenes are so dynamic. As Casper, Flores has the old-man-in-a-young-body quality of Franco Citti in Accattone. With that dainty tattooed teardrop under his eye, it's almost as if Casper knew he was going to end up as the sensitive main character in a film about a gang member turning his back on crime. His leader, Lil' Mago (Tenoch Huerta Mejía), has a clown tattooed on one arm, tombstones on his torso, and what appears to be an enormous bar code on his face, which must cause havoc at the supermarket checkout. The cumulative effect is like a human version of the doodle pad you keep next to the telephone.

Lil' Mago's cruelty is so excessive it's almost comical. It isn't enough for him to oversee the execution of a rival; he has to do so while cradling an infant in a Babygro. (The child doesn't stir when a gun goes off in his immediate vicinity. You could read that as an error - the noise was clearly dubbed in later - or a sign of the ubiquity of gunplay.) Lil' Mago provides the menace while Sayra's bid to flee Mexico and Casper's struggle to elude capture drive the narrative. But the heart of Sin nombre is 12-year-old Smiley (Kristyan Ferrer), so named because he emerges from his initiation grinning through a glaze of blood. When Casper goes on the run, it is Smiley who wants to settle the score. "Send me to find him and kill him," he pleads, which is horribly funny; the wee shrimp looks scarcely old enough to walk to the shops on his own.

The writer-director, Cary Fukunaga, tends not to hint at something if it can be broadcast by loudhailer instead. ("We both know loss," Casper tells Sayra in one of the clumsier moments.) But his film vividly articulates the allure of gang life. Once Smiley is sworn in, Lil' Mago says: "Now you're part of a family with thousands of brothers. Wherever you go, there'll always be someone to take care of you." Who wouldn't want that? (It's what Sayra craves.) Sure enough, Smiley has only to mention the brotherhood on his travels to be offered sustenance.

Where Sin nombre falls down is in neglecting to lend a comparative clarity to Sayra's journey. The film might not feel so conflicted if it brought the same hyperbolic excitement to the immigrant dream as it does to its portrait of gangland honour. When one of the characters does reach the United States, it isn't the Statue of Liberty that awaits, as it was for young Vito Corleone in The Godfather: Part II, but an unpromising retail park, magnificent in its banality.