[T]he South Korean filmmaker Lee Changdong uses reserve to tremendous effect. Mr. Lee’s latest, Poetry, which is also in competition, centers on Mija (Yoon Jung-hee), a grandmother raising her only grandchild, a teenage boy, in a small city. At first, this seemingly simple story concentrates on Mija’s daily habits, her visits to her doctor, her relations with her grandson, her poignant vanity. One day she decides to take a poetry writing course, a decision that, as the tale takes a violent turn, becomes our entry into a woman who’s far richer than her fussy habits and humble words suggest. With an understated visual style and perfectly paced narrative, Mr. Lee has created a portrait of a woman who has, by the end, become an extraordinary vision of human empathy.