On Sunday mornings on a street corner in East Los Angeles, a pretty young woman named Rosario (Kate del Castillo) makes her way past the pizza joints and tattoo parlors to a pay phone. Sunday is when she calls home.

That's when her boy, Carlitos (Adrian Alonso), knows to stand by the phone in a neighbors house in their Mexican village.

Rosario still wears a nasty scar from the night she was smuggled across the border four years before. She hasn't seen her son in all this time. He lives with his grandmother, anxiously waiting for mom to save up enough cash to get her legal status changed and Carlitos sent to her.

Whenever you miss me, Mom reassures him, just look up at the moon. She'll do likewise, because however far apart they are, at least they're "Under the Same Moon," the English translation of the title of this Spanish language (with English subtitles) film.

Then comes the fateful week that Grandma dies, that Rosario loses her job and, desperate to get her boy back, decides she should hastily marry a willing man who has his U.S. citizenship.

Carlitos, rather than fall in the clutches of the family of a father he has never met, resolves to go to Mom. He pays inept American college kids (America Ferrera of "Ugly Betty" is one) masquerading as "coyotes" (smugglers), and his odyssey begins.

There is but one modern American immigrant narrative: Courageous poor people endure danger, venal coyotes and "La Migra" (the INS Border patrol) to make it to the land of milk and money. Sending a child on this journey creates a wonderful empathy that earlier versions of the quest lack. We fear, at every turn, for the boy's safety.

Will he survive the crossing? Will La Migra catch him? Is a junky he meets friend or foe? What about the members of the Latino undocumented underground he falls in with?

All the while, Mom is prepping for what could be a less than loving marriage, and that clock is ticking away toward the moment, the following Sunday, when she makes her call, realizes her mother is dead, that her son is missing, that all her sacrifices may have been in vain.

First-time feature director Patricia Riggen is from Mexico. Working from a script from veteran TV writer Ligiah Villalobos ("Ed," "Walkout"), Riggen handles this ticking-clock suspense well.

Like the best road pictures, this one has episodes that interrupt the trek every few miles -- a tomato farm where migrants do the dangerous, tedious work of picking (pesticides); a American Indian roadhouse where adorable Carlitos can wash dishes; bus-station predators.

It's a tale peppered with colorful characters, none more intriguing than fellow illegal Enrique (Eugenio Derbez), a laborer on the run and very reluctant to take on the responsibility of a kid, no matter how cute the rest of the world thinks Carlitos is.

The movie has a few too many unsympathetic "gringos," venal employers, scary Border Patrol agents and the like.

But the engaging mother-son story invites us in. And its larger theme, that America's great historic immigration narrative has merely changed accents from Italian or Irish or Eastern European to Latin American, is what we remember.

Wherever we came from, however we got here, we have more in common than we think.