An appropriate review for “Under the Same Moon,” which opens today in the city, might take the form of a poem, or maybe that of a photo album — something that could stir emotions and bypass the tedium of detail or logic. Poetry is less about the rules of language than the underlying meanings, and so it is with Patricia Riggen’s sincere, somber, but sloppy drama about illegal immigration, a film of admirable sentiment that lacks the narrative glue to help it stick to the mind as effectively as it does to the heart.

Still, it’s hard not to be enticed by the winning duo of young Adrián Alonso and the beautiful Kate del Castillo, the two vulnerable and captivating spirits struggling at the center of this turbulent drama. While it takes a while to meet Rosario (Ms. del Castillo), we meet Carlitos (Mr. Alonso) at the outset. He lives with his grandmother in Mexico, and is shocked to learn from a relative that his father is not dead but merely living across the border in the same country as his mother.

Carlitos is the embodiment of a wave of de facto orphans living in Mexico, the sons and daughters of loving parents from whom they have been separated by the border. While the adults have taken the dangerous and illegal journey through the deserts in search of better wages, their young ones have stayed behind. In the case of Carlitos, his only link to his mother remains a weekly phone call, made from a pay phone somewhere in Los Angeles. Rosario loves her boy, but she knows that visiting him means never returning to her “high-paying” job cleaning houses.

More than anything, Ms. Riggen seems determined to counter pervasive stereotypes regarding illegal immigrants, ones that often deem them a plague of locusts rather than human beings. In “Under the Same Moon,” the director uses such disarming archetypes as a frightened little boy and a distraught mother to flip the perspective 180 degrees and offer us a chance to see the world through an illegal alien’s eyes.

When Carlitos’s grandmother dies, he reaches out to one of her business contacts and secures passage through the American checkpoint. Ms. Riggen puts us in the young boy’s crawl space, hidden under the floorboards of a minivan, and we listen to his panting as the sweltering car is inspected by border agents. Once on the other side, Carlitos wanders Texas alone, and we share the boy’s isolation, wondering along with him how he’ll make it to California. When he finds temporary work washing dishes and picking crops, we become immersed in the monotony of hard labor and the panic that erupts when federal agents conduct a raid.

All the while, Rosario, unaware of her son’s dangerous road trip, struggles with her own issues. When one of her two wealthy employers casually dismisses Rosario, her boss does not realize that the termination is a death blow for the young mother. Increasingly desperate to see her son, Rosario repeatedly flirts with the idea of marrying an American who expresses interest. When she learns that her son is en route to her, we feel her terror when she realizes that, without a reliable address or phone number, he has no way of finding her.

Unfortunately, the movie is unquestionably too long, and the zigs and zags of Carlitos’s adventure grow increasingly unlikely, even irksome. But the story keeps surging forward with emotional, affecting performances by both Mr. Alonso and Ms. del Castillo. As a diligent woman determined to find work, Ms. del Castillo exhibits a quiet but ardent sense of determination, one that becomes even more prominent as she considers a loveless marriage as a means to an end. Unlike so many other child actors, who swing too easily between emotional extremes and who tend to overplay their parts, Mr. Alonso, 13, exhibits a remarkable versatility. He’s vulnerable and vicious, naïve at times but knowing at others, and there’s a fire to him that belies his age.

For all its flaws, “Under the Same Moon” pushes back against prejudice with an exercise in empathy. Rosario and Carlitos may be breaking the law, but as we are plunged into their fear and their joy, it’s impossible to dismiss them.

ssnyder@nysun.com