As evidenced by the rapturous standing ovation the film received at its Sundance world premiere, helmer Patricia Riggen and scribe Ligiah Villalobos touch some mighty powerful chords with their highly accessible story of a woman and her son separated by the U.S.-Mexico border.

Hoping to make a better life for herself and her son Carlitos (Adrian Alonso), Rosario (Kate del Castillo) crossed the border illegally four years ago and now works in Los Angeles as a cleaning lady. Carlitos, 9, yearns to be with his mom but still lives in Mexico with his grandmother (Angelina Pelaez), who helpfully speeds along the reunion by passing away one night.

With the unwitting aid of his employer Carmen (Carmen Salinas), who runs a business smuggling people into the States, Carlitos makes arrangements to stow away in a minivan driven by two Mexican-American students (Jesse Garcia and "Ugly Betty's" America Ferrera). In one of the script's many instances of shrewdly if shamelessly tightening the screws, Carlitos crosses the border safely but is separated from his smugglers when their vehicle is unexpectedly impounded -- the first of several setbacks in what is destined to be a difficult journey.

As Carlitos makes his way from Texas to California, Rosario -- unaware that anything has gone wrong -- continues to mope about her dead-end situation, entertains the idea of marrying a hunky Chicano named Paco (Gabriel Porras) for green-card privileges, and is treated most unjustly by her by her rich, snooty (and not coincidentally, white) employer (Jacqueline Voltaire). It's this tendency toward caricature that leads one to wonder, when Paco offers his views on Americans -- "First they screwed the Indians, then they screwed the slaves, and now they're screwing us Mexicans!" -- whether pic has anything more nuanced or even-handed to offer.

Riggen and Villalobos prove much more deft at handling feelings than ideas, and ultimately the film's parallel narratives -- anchored, respectively, by tyke thesp Alonso's mug-free performance and del Castillo's fiercely sympathetic turn as a mom at the end of her rope -- develop a surging emotional momentum that all but overcomes one's initial reservations. The already overstuffed tale even gives Carlitos a father figure in Enrique (Eugenio Derbez, excellent), a fellow illegal who initially can't stand his pint-sized tag-along but ultimately learns the meaning of friendship, yielding welcome reserves of warmth and humor.

Pic juggles multiple plot strands in the final stretch of its mission to reunite Rosario and Carlitos, most of them cleverly worked out but rather belabored, including one especially ill-advised encounter with a figure from the past.

Tech credits are strong, from the vibrant hues of Checco Varese's nimble lensing to the equally vibrant soundtrack; popular norteno band Los Tigres del Norte has an amusing onscreen cameo. Carlo Siliotto's original score has a tendency to turn alarmingly percussive whenever police cars or border patrol officers show up, lending further credence to the idea that pic will be best appreciated by those who share its political point of view.

Camera (FotoKem color), Checco Varese; editor, Aleshka Ferrero; music, Carlo Siliotto; music supervisor, Lynn Fainchtein; production designer, Carmen Gimenez Cacho; sound, Santiago Nunez; supervising sound editor, Joe Milner; assistant director, Yvette Gurza; casting, Manuel Teil. Reviewed at Sundance Film Festival (Spectrum), Jan. 21, 2007. Running time: 109 MIN. (Spanish, English dialogue)
 

With: Carmen Salinas, Angelina Pelaez, Gabriel Porras, Maria Rojo, Ignacio Guadalupe, Mario Almada, Ernesto D'Alessio, America Ferrera, Los Tigres del Norte.