Some people are just better off dead. That’s the ultimate conclusion of the prolific French filmmaker François Ozon’s new domestic drama When Fall Is Coming, receiving its world premiere at the San Sebastian Film Festival this week, but delivered with such sly delicacy, such slippery grace — no, actually, such sweetness — that there is simply no arguing with it.

Those qualities — delicacy, grace and sweetness — are largely encapsulated within the tidy person of Michelle. Michelle is the heroine of her own small but satisfying life and quite a few other lives besides, a woman with the time and inclination to be kind. On the day we meet her, she is driving her best friend to the prison where her son Vincent (Pierre Lottin) is being held. Visiting a prison is draining. Michelle waits outside, ready to listen to Marie-Claude...