The plot hinges on a quirky French law of property, the viager. An owner can sell a house or an apartment for a low fee on the condition that the now-former owner remains in residence until death. A purchaser might luck out and acquire a residence from someone who then speedily goes to his reward; he might also end up laying out cash for someone who stubbornly refuses to give up the ghost and the right to occupancy.

Mathias Gold (Peter Friedman), the protagonist of My Old Lady, is one of the unlucky ones. A fellow who twice says of himself "I'm such a loser" and once declares "I am so pathetic," Mathias, 50, has traveled to Paris to take possession -- or so he thinks -- of a dark, sprawling, top-floor apartment overlooking the Luxemburg Gardens. Arriving during one of those spirit-dampening local downpours, he discovers that 94-year-old Mathilde Giffard (Siân Phillips) resides in the apartment with her daughter, Chloe (Jan Maxwell). So Mathias, who has spent his last penny flying from the states, cannot quickly sell the place, as he'd planned; he must pay $2500 monthly until the vigorous, quick-witted Madame Giffard -- who insists she's only 92 -- turns up her Gallic toes.

But Mme. Giffard, a former teacher, is willing to rent Mathias her late husband's gun-racked bedroom, an accommodation Mathias has no choice but to accept. Chloe is so upset by the arrangement and Mathias's refusal to quit the premises that she tells him, "I will destroy you." Her reasons for such an extreme outburst are not clear at first, particularly when she says something cryptic to her mother about Mathias's having the same face as a for-the-moment-unidentified someone.

Before long, however, the person to whom she refers is revealed: It's Mathias's recently deceased father, Max, who bought the apartment and then willed it to his only remaining son, along with a couple of cartons of French books. Since Max and Mathias (who has written two unpublished novels himself) were not close, Mathias becomes increasingly puzzled about why he's been left the extravagantly high-ceiling abode -- the latest of set designer John Lee Beatty's breathtaking stage domiciles. He spends the rest of his unsettling stay trying to figure out his father's relationship to the apartment and to the Giffards.

Siân Phillips, Peter Friedman, and Jan Maxwell do their usual yeoman-like jobs of bringing parts to life, and they've been guided expertly by director David Esbjornson, who sees to it that they aren't dwarfed by the tarnished and shadowy set (lit by Peter Kaczorowski). If stood next to an actual 94-year-old, the clever Phillips might not seem 94, but she's remarkably convincing in her gray wig and sensible shoes; and when Mme. Giffard has to twinkle or be enigmatic, Phillips has the right tools. Friedman, somehow suggesting Horovitz himself in costume designer Elizabeth Hope Clancy's knockabout duds, shies away from no emotion but also never goes too far with it. In the sequence where, still uncorking wine, he uncorks his mother's story, he is especially moving. So is Maxwell, who holds on to her sixth arrondissement accent with aplomb and looks as beautiful as described by the script. There is incidental music, provided by Peter Golub, that establishes the right mood, and the Django Reinhardt numbers that sound designers Jon Gottlieb and Matthew Burton include have the tartly heart-rending quality that Horovitz goes for but just misses. The title My Old Lady sounds like something an aging rocker might mumble, and it seems inappropriate to this unrealized play.