Blood ties govern this searing drama about illegal immigrants heading from Central America through Mexico to the United States. An impoverished teenager from Honduras (Paulina Gaitan) hops aboard a freight train with her uncle and father to join the father’s new wife and kids in New Jersey; in Mexico they encounter a young thug (Edgar Flores) at odds with his own adoptive family, the brutal international gang known as Mara Salvatrucha. Writer-director Cary Fukunaga keeps the story lean while peppering it with realistic details – like the local markets that spring up around the train tracks to service and cheer on the passing emigres. The supporting cast is a mix of professionals and amateurs; the standouts are Tenoch Huerta Mejia and Luis Fernando Peña, terrifying as the Mara’s tattooed leaders, and 14-year-old Kristyan Ferrer as their new, deadly earnest recruit. In Spanish with subtitles. R, 96 min.