Though it appears to be about the travails of illegal immigrants, "Under the Same Moon" ("La Misma Luna") is a powerful and evocative account of the efforts undertaken to forge a perilous mother-and-child reunion. It is a moving tale of yearning, as well as unflagging courage and determination.

This often wrenchingly moving film -- about a 9-year-old boy searching for his mother across the U.S.-Mexico border -- exerts immediate, irresistible power, combining an affecting story, indelible characters, urgent topical relevance and superbly calibrated sentimentality.

Thanks to the uncommonly shrewd judgment of screenwriter Ligiah Villalobos and director Patricia Riggen, both newcomers, "Under the Same Moon" never feels like rank exploitation, even as it steadily aims for the emotional jugular.

"Under the Same Moon" approaches the controversial and fraught issue from a compelling emotional angle, one that hasn't been covered in recent films. It raises a specific and probing question: Is Carlitos better off living in poverty, with his loving mother at home to care for him, or separated from her but in greater comfort with more possibilities for a better future?

This straightforward story of a boy and his mother wisely avoids oversimplification of a complex social question. It is poignant, even unabashedly sentimental, without being overwrought or sugary sweet.

And the acting is honest and understated, particularly the engaging portrayal by young Alonso, as well as strong performances by del Castillo and comedian Eugenio Derbez, both big stars in Latin America.

If "Under the Same Moon" dramatizes a serious, even potentially tragic story, the tone never succumbs to unremitting grimness. Instead, the filmmakers regularly leaven their story with little unexpected grace notes of humor and tender irony.

Which isn't to say they don't ratchet up those twists to an almost excruciating degree. The fact that "Under the Same Moon" has been crafted with such an adroit, sensitive touch should reassure viewers that, as it approaches its utterly gripping climax, their hearts are in good hands, too.