The pleasant surprise of Israel Horovitz’s directorial debut, which he adapted from his own play, isn’t that it transcends staginess. Horovitz has screenwriting experience, so he knows the movie medium makes unique demands. What’s surprising is how an ostensible light-comedy kit assembles itself before our eyes into something subtle and serious. Just look at this set-up: An aging and destitute New Yorker (Kevin Kline) hopes to sell off the Paris apartment willed to him by his estranged late father, but finds an old woman (Maggie Smith) living there, with her chilly daughter (Kristen Scott Thomas), and allowed by a quirk of French real-estate law to do so until death. Then there’s the safe-seeming casting, with Kline as mildly seasoned American wise-ass, Smith as elderly Englishwoman who sits around a stately property dispensing quips, and Scott Thomas as paragon of mature bilingual skepticism. But actor-friendliness pervades Horovitz’s writing and direction, and the cast thrives in what becomes a collective close inspection of intergenerational battle scars. Shrewd filmic additions also include the peculiar French character actor Dominique Pinon as a houseboat-dwelling real estate agent, and several elegantly played flourishes of authentically Parisian romance. My Old Lady does honor its theatrical roots, mostly just by honoring the human understanding that inspires people to write plays in the first place.