Korean filmmaker Lee Chang-dong’s latest, a Cannes screenplay prizewinner last year, opens on an effortlessly lyrical moment. Only after we determine that yes, that is indeed a dead teenage girl floating face-down in the river on this otherwise lovely day, does the title fade in: “Poetry.” Something in the shimmering surface, the silence, tells us it is not a glib joke.

Then a shy, sixty-something grandmother and part-time housecleaner (Yun Jung-hee), slowly losing her mind to Alzheimer’s, decides to take a poetry class at her small town’s cultural center. The teacher says, “Poetry is all about discovering true beauty in our everyday life.” That’s not a joke either. The only assignment for the duration of the class is to write one poem.

Lee might as easily have called the film “Suicide,” for we learn soon enough that the girl killed herself, after enduring repeated sexual assaults from a group of boys at school. And we learn that the old woman’s sullen ingrate grandson (Lee David) might be among the perpetrators. But “Poetry” it is. That single-word, with its patina of peculiar irony, and itself a metaphor, but for what? Do we read what we’re seeing here as a genuinely redemptive antidote to life-denigrating violence or as a trifle of frivolous escapism? How do we cope with the possibility that it’s both?

Lee’s delicate, declaratively wistful tone is a major achievement when you consider how angry this movie could be, how much righteous feminist rage it might deservedly summon. In addition to the reflexive discourtesy she absorbs from her grandson and from the infirm old man (Kim Hira) who pays her to feed and bathe him, the old woman finds herself summoned to a lunch with the fathers of her grandson’s classmates, who consider it a given that she’ll help them bribe the dead girl’s mother for silence. Her quietly bewildered response is to wander outside, open her notebook and try getting started on that poem.

Yun reportedly came out of retirement for this role (she’d already been in more than 300 other films), and her apparently boundless expressiveness is a great boon to Lee, whose style seems sometimes to consist entirely and very wisely of just watching her face. Only in this way, perhaps, can an incantatory melodrama about compound failures of language seem so articulate.

The teacher also says the hard part about writing a poem isn’t writing it but finding the heart to write it, and that too might seem a little on-the-nose had the movie not so affectingly dramatized it. Here we have poetry as purification, the barbed and bruising achievement of grace.