First-time director Fernanda Valadez conjures up a vision of real evil in her story of the terrors faced by migrants into the US

There is unbearable heartbreak in this migrant drama from first-time Mexican film-maker Fernanda Valadez – and also a vision of real evil. At times, it looks something like social-realist folk horror. Mercedes Hernández plays Magdalena, a middle-aged woman from Guanajuato in central Mexico whose teenage son Jesús left home three years before, with a friend, on a bus bound for the border, where he’d hoped to take his chances on disappearing into the US as an illegal. But the body of Jesús’s friend has been found on Mexican territory, in an unspeakably grim holding area where the corpses of teen runaways are routinely kept in container boxes awaiting identification – though there is still no proof that Jesús himself is dead.