Jean Cocteau’s 1948 French feature, adapted from a play produced a decade earlier, is both a lesson in mise en scene and an illustration of the paradox that accentuating the theatrical aspects of theater on-screen can make them quintessentially cinematic. (To my knowledge the only other film that does this to the same degree is Kon Ichikawa’s An Actor’s Revenge.) The accomplishment becomes all the more impressive if one considers Cocteau’s mannered and affected story: the sheltered son of a middle-aged couple who live with the wife’s unmarried sister falls for a young woman without realizing that she is his father’s mistress, and the mother’s terror at the prospect of losing her son is matched by the mistress’s terror of being exposed. Individually the characters might seem outlandish (the son is awfully green for someone in his 20s), but collectively they validate one another as the plot unfolds in two claustrophobic flats, and the cast is masterful: Jean Marais, Josette Day, Yvonne de Bray, Marcel Andre, Gabrielle Dorziat. Cocteau’s cuts and camera movements are both eccentric and definitive. In French with subtitles; an archival 35-millimeter print will be shown. 98 min. Gene Siskel Film Center.