Writer-director Noah Baumbach’s new feature ventures further into the family-meltdown milieu he so deftly mined in The Squid and the Whale. When her estranged, formerly flighty sister (Jennifer Jason Leigh) plans to marry a mopey underachiever (Jack Black), an emotionally brittle author (Nicole Kidman) shows up at the family beach house to make trouble. Oh, and she brings along her sensitive preteen son (Zane Pais). Don’t worry: Baumbach is more afraid of mawkish melodrama than you are—so much so that his dark, funny movie seems a little proud of being so biting. Even still (and thank goodness), the filmmaker does cherish his characters, who treat each other with jittery, real-seeming tenderness and terror and contempt, and Margot never overplays its deep-black comedy. Black stumbles here and there, but fine work from Kidman and Leigh (Baumbach’s wife, by the way) and exceptional work from Pais, makes up for it. Rendered in a swift series of lean, less-is-more scenes, the film moves breathlessly; that it’s full of loose ends is precisely the beauty of it.