WHY NOT!-(Pourquoi Pas) At the Outer Circle I, with subtitles.

Living together in threes is a favorite subject in French films. "Triad," the English word for it, doesn't sound like nearly as much fun as menage a' trois .

There was "Jules and Jim," and "Cesar and Rosalie," and now "Why Not!" advances the possibilities of group living. This is the first feature film by writer-director Coline Serreau, and while not of Jules-and-Jim caliber, it's a good effort, sometimes witty, sometimes bittersweet.

Louis' mother is crazy, and he is a bit of a mad musician himself.

Alex just split with a chauvinist husband.

And Fernand's former wife won't let him see the kids, though he's a better mother than she is.

When they go to pay the rent, the little landlady feeds them cakes and tea, and wonders aloud: Is Alexa married to Louis or Fernand?

Since the landlady is a tad deaf, they reply by smiling amiably and fidgeting. "Well, as long as it works," she concedes.

In fact, Alexa and Fernand are lovers. Louis and Alexa are lovers and Fernand and Louis are lovers. This group household works out of mutual need and an enlightened division of labor.

Louis, a sad-funny Chaplinesque part played by Mario Gonzalez, provides the background music with piano and guitar.

Alexa pays the rent on their house by reading to an old lady. The film debut of Christine Murillo, it's an earthly role of a woman finally free and enjoying it: "I don't mind earning the money," she says. "I hate housework."

The viewer can't help but despise Alexa's estranged husband, who looks like a weasel. He begs her to come back chiefly because his business image requires a wife.

When the old lady dies in the middle of a page, Alexa goes to him for the rent money. A couple is visiting, the husband an "important business contact." When Alexa can't tolerate the inane conversation and tries to leave, her husband pulls her into the bathroom and beats her up.

The couple overhears the clatter of the fracas and gaily implores: "Don't fix anything fancy for us!"

It's Fernand, portrayed by Sami Frey, who cements the group, gives it purpose and does its laundry. Fernand is strong and handsome, cherishes his vacuum cleaner and mothers his two friends, who substitute for the children he's lost.

Then along comes Sylvie.

Well, why not?