There’s no defending what Anne, a successful lawyer and mother, does when she begins an affair with her 17-year-old stepson, Théo, in the incandescent French drama “Last Summer.” And the director, Catherine Breillat, does not try to defend her, nor condemn her. That’s because her bracing new film is above all a study of human behavior, when the follies of desire knock even the most settled life off its axis.
When Anne and Théo do have sex, she says it must never happen again, but of course it does. Without centering sex scenes or seduction, the narrative makes it clear that the affair continues, while Anne almost absurdly tries to conceal it from her husband. There’s nearly a “don’t go into the basement!” quality to witnessing Anne’s helpless fascination and the pair’s libido-addled decision-making.