Imagine a more subtle, less arch Lord of the Flies, set in a well-to-do Buenos Aires suburb. OK, yes, that is sort of hard to imagine. And it wrongly implies, besides, that A Week Alone is preoccupied with some kind of salable high-concept. It isn’t, but it is indeed a movie about what happens in a gated community when the grown-ups go away on vacation together, leaving their kids and young teenagers supervised, sort of, by a 22-year-old family maid (Natalia Gomez Alarcon). What happens isn’t really all that much, actually, at least not until the maid’s younger brother (Ignacio Gimenez) shows up and reminds the rest of them that there is such a thing as a poorer neighborhood. Director Celina Murga, co-writing with her husband and producer Juan Villegas, has a light enough touch to explore adolescent ennui and melodrama without indulging in it, and enough respect for her audience not to goad rhetorical class warfare. She makes the point without belaboring it that as far as the construction of character is concerned, a laissez-faire attitude works much better in plotting than in parenting.