A good journalistic drama can lend clarity and heart to a social issue can glue it together logistically and emotionally in a way that a hundred newspaper articles and furrowed-brow TV segments can't. Under the Same Moon zeroes in on illegal immigrants from Mexico, and before you can say, ''Wow, that sounds boring,'' director Patricia Riggen has smuggled us, with no-bull authority, into the rituals, jokes, and survival games of a culture of half-existence: people who live in two places and nowhere at all.
Carlitos (Adrián Alonso), who is 9, hasn't seen his mother in four years. She lives in L.A., where she works as a housekeeper and sends him $300 a month; after his grandmother dies, he heads north to reconnect with her. Carlitos has a sweet pup's face, but he's a wily little tyke who makes it across the border in no time, then bounces around amid the culture of illegals, working as a dishwasher, picking hothouse tomatoes, drifting with a shifty grouch of a migrant worker (the terrific Eugenio Derbez) who keeps them both a step ahead of the feds. As Carlitos' mom, Kate del Castillo catches the bottled-up desperation and hope of a life that teeters between opportunity and slavery. Under the Same Moon's politics sneak up on you. The film says that the U.S. immigrant situation is untenable, but then it forces us to ask: What should be done? That's a good enough ''argument'' to find in a movie with an ending so touching it could make Lou Dobbs cry. A–