The director Patricia Riggen with Adrian Alonso on the set of “La Misma Luna” (“Under the Same Moon”)

It seems fair to say that in the world today there are not many stories bigger or more complicated than the movement of large groups of people from one country to another.
And yet, perhaps because it is so vast and complex, it is a story that can be comprehended only in its neatly dissected, human particulars.
An age-old piece of Hollywood wisdom holds that every narrative arises from one of two situations: Someone goes on a journey, or a stranger comes to town.
The immigrant’s story, in its basic form, fulfills both of these archetypes.
An individual or a family leaves a familiar world, by either choice, necessity or some perceived combination of the two, and arrives in a place that is as strange to the newcomers as they are to it.
In the United States, Western Europe and other relatively wealthy parts of the world, immigration is currently a subject of raw political contention.
As such, it is a topic that tends to be discussed both heatedly and somewhat abstractly.
Organizing all this argument and emotion into stories has become an especially acute and fruitful challenge.
Of course, variations on the two-fold tale of departure and arrival have been a literary staple, especially in the United States, for more than a century.
But until recently these themes have never been quite as ubiquitous on movie screens.
Though the American film industry was founded largely by enterprising immigrants and has been fed by successive streams of talented emigres, Hollywood has generally preferred to depict an idealized, homogeneous America, where the nonwhite and the nonnative linger in the margins and the shadows.
The exceptions have mainly been examples of the backward-looking, second-generation tradition, films like the “Godfather” cycle, an ambivalent epic of an Italian family’s incomplete Americanization, or “Fiddler on the Roof,” a sentimental journey back to the world of the Eastern European shtetl .
Knowing how the story ends .
with Americans paging through their family albums, marveling at what their ancestors had been through .
gives even the painful passages in stories like these a warm, soothing glow.
Retrospect also helped make the experience look simpler than it may really have been and certainly simpler than what confronts the world now.
Those films, and others like them, traced the passage from a premodern, peasant way of life into a modern world of cities, factories and social mobility.
“Golden Door,” a recent film by Emanuele Crialese, an Italian director, reenacts this transition in an especially stark and powerful way, bringing an extended family from a poor, rural corner of southern Italy up to the edge of New York City and leaving the viewer to imagine what the new arrivals find when they cross the threshold.
Mr. Crialese also recalls an era when global communication relied on steamships and telegraphs and when differences of language and custom seemed more profound than they might today.
“The Golden Door” uses the medium’s powers of empathy and estrangement to measure the enormous distance its characters travel.
But in the present, the distances have shrunk.
Movies that deal with migration in the modern world tend to emphasize the often disconcerting connections that seem to web the Earth and link people whether they are aware of the links or not.
Their stories are, perhaps as a consequence, less linear, shuttling between places and times rather than moving irreversibly from one to the other.
And the camera too crosses borders, traveling, perhaps with deceptive ease, from one country to another without necessarily coming to rest anywhere.
In “La Misma Luna” (“Under the Same Moon”), a new film from the Mexican director Patricia Riggen, a young boy and his mother live on opposite sides of the United States-Mexico border, she in Los Angeles, he in the town she left when she moved north.
In some ways, they live in different worlds, and Ms. Riggen takes note of the small, everyday details that distinguish one place from the other.
But they are also connected by telecommunications and by the director’s narrative method, which cross-cuts between them as they move toward a possible reunion.
Carlitos, the boy, sets out across the border, while his mother, Rosario, contemplates a journey home, an escape from hard work and the constant fear of deportation .
Ms. Riggen’s narrative strategy is, in some ways, a simplified version of the multistranded storytelling found in movies set abroad, like “Babel.
” “Babel,’’ released in 2006, is not, strictly speaking, an immigrant tale, but it uses the global flow of people and information as a theme and a plotline.
And like “La Misma Luna,” it takes pains to point out that inequality and exploitation, along with isolation and estrangement, are features of the global economy.
They offer an implicit critique of the optimistic, tolerant multiculturalism that has become a central feature of modern American ideology: a more fatalistic sense of contradiction and complication.