Sin Nombre 

If you took away the vampires in Twilight and replaced them with Mexican gangbangers, you might have something like the central plot of Sin Nombre [Without Name]. You’d also have a way scarier movie.

A Honduran teen named Sayra (Paulina Gaitan), uprooted from her home and forced to march north by a father she barely knows, meets a handsome boy (Edgar Flores) who rescues her from an attacker. The thing is, her savior’s a dangerous man himself — so dangerous he’s afraid to get close to her. The two young people, both of them gloomy, stoic and withdrawn, nonetheless build a rapport. When her new friend hops off the train carrying her family toward the U.S. border, Sayra has to make a life-changing decision. Love or family ties? Take a guess.

Of course, it wasn’t the star-crossed-teen-romance angle per se that won first-time director Cary Fukunaga a directing award at Sundance. (Sin Nombre also snagged a highly deserved win for cinematography and a nomination for the Grand Jury Prize.) Like last year’s Frozen River or the upcoming Precious, Sin Nombre transports American arthouse audiences to a world most of them know almost nothing about except that they should know more. The film depicts rural Mexico as a hotbed of color and vitality, but also of indigence and desperation, where legions of people camp out on the roofs of moving freight trains in the hopes of getting close enough to jump the border into Texas, the promised land of Wal-Mart and Six Flags.

The border doesn’t mean as much to gangs such as the Mareros, which operate on both sides with seeming impunity, preying on vulnerable immigrants and ruthlessly squelching dissent in their ranks. At the beginning of the film, we watch the brutal initiation of a sweet-faced preteen (Kristian Ferrer), to whom the gang offers security and excitement he can’t find elsewhere. (It also gives him a new name, “El Smiley” — hence the film’s title.) But membership is a lifetime thing — “womb to tomb,” like the Jets used to sing. As the local ringleader (Tenoch Huerta) shows Smiley how to execute a rival, he dandles a baby on his hip.

The older El Casper (Flores), who serves as the boy’s mentor, is chafing at the bit; he’s been spending too much time with an upscale girlfriend his “homies” don’t know about, a recipe for trouble. When he breaks free, he does so with a violence that makes him, in effect, a walking dead man. But he also reclaims his real name — and his humanity — in his friendship with Sayra.

As this synopsis suggests, Sin Nombre has many plot threads, not always well knit. The script (also by Fukunaga) evokes a score of gangland-melodrama clichés. But it never fully fleshes out its main characters; by the end, we know more about little Smiley than we do about Casper, the male lead, who remains almost as mysterious to us as to Sayra.

What it lacks in conception, though, the film makes up in atmosphere, visuals and charismatic performances. Shot in the saturated colors of National Geographic, but a lot less sedate, Sin Nombre brims with stunning landscapes and equally striking squalor. Though his action scenes are a little spastic, Fukunaga has an artist’s eye for detail; he turns cluttered rooms and piles of dying vegetation into still lifes, and he gives the same loving attention to the gang members’ tattoos.

By the end, we may feel as if we’ve lived for an hour and a half in this world. The film has one indelible personality in Gaitan’s taciturn emigrant, who says a lot with just her hooded eyes. We don’t know what she left behind or what she hopes to find in New Jersey, where her dad already has a second family. But we do know she’s the kind of girl who takes fate into her own hands. If teen romance is always about flirting with danger, Sayra is willing to move past the flirting stage, with consequences we’d never see in the sheltered world of Stephenie Meyer. Who needs vampire stories when your real life is a horror show?