In Arnaud Desplechin’s beguiling A Christmas Tale (Un conte de Noël), Catherine Deneuve brings her legendary poise to the role of Junon, matriarch of the troubled Vuillard family, who come together at Christmas after she learns she needs a bone marrow transplant from a blood relative. That simple family reunion setup, however, can’t begin to describe the unpredictable, emotionally volatile experience of this film, an inventive, magical drama that’s equal parts merriment and melancholy. Unrequited childhood loves and blinding grudges, brutal outbursts and sudden slapstick, music, movies, and poetry, A Christmas Tale ties it all together in a marvelously messy package.