Firing off a deluge of immigrant-hardship vignettes with the thudding consistency of a tennis-ball machine, Under the Same Moon presents a genre somewhat at odds with itself: the gritty fable. Last year’s The Italian, another story of a small boy’s picaresque search for his mother, struck a balance between the awful and the wondrous by surrounding the hero with a whiff of Grimm grotesque, in which it’s hard to tell the truly strange from the general strangeness of being a child. Director Patricia Riggen’s tone is too gauzy to cohere the perspectives of nine-year-old Mexican Carlitos (Adrían Alonso), who crosses the border alone when his grandmother dies, and his mother Rosario (Kate del Castillo), a Los Angeles maid who hasn’t been home in four years. Many of the scenarios don’t translate the immediacy of Carlitos’s jeopardy or Rosario’s heartache (the border trauma, the Bel Air bitches, the ICE raids), recalling instead distractingly similar moments in films like Babel and Fast Food Nation. Alonso, an expressive, ingratiating actor, develops a textbook rapport with Enrique (Eugenio Derbez), a grizzled illegal whom he drafts as an escort, but the duo’s travels never gain a traction of their own, and the film’s destination feels overdetermined despite its sweetness.