A.R.Gurney's "Sylvia" is an unpretentious valentine of a comedy with a small cast, a cozy theme, and nothing too hard to think about except a triangulated relationship between a man, his dog and his wife. Can a man's dog come between him and his spouse?

Sylvia, the dog, follows the man home from the park one day, and he decides to keep her. But the man is very vulnerable — he's an empty-nester whose career is on the decline, just when his wife's is beginning to pick up speed. Losing his head over a new pet could jeopardize his job and his marriage.

But the playwright and director Gary Morris keep things light and breezy, and the cast in The Actors' Group production plays it for quirky fun. The quirky quality comes from a dog part to be played by an actress with pronounced canine mannerisms.

Becky Maltby fills Sylvia with hyperactive energy and gives her a shrill bark and a worshipful gaze that turns her master into a god. She also speaks to him in perfect English, which he returns as if it were the most natural thing in the world.

Tom Holowach plays the man as an amiable fellow whose flagging interest in his work opens him up to the interesting new role of dog owner. Euphrosyne Rushforth is the wife who is fully engaged in a delayed career of teaching Shakespeare in Junior High.

It's the conversation between the dog persona and the humans that gives the play its edge and supports it through two acts of predictable and unremarkable action.

Sylvia mostly wants to sleep on the couch and get her tummy scratched, but some of her best scenes come from articulating doggie emotions via colorful human speech.

There's a riotous moment when Sylvia loses control after spotting a cat lurking under a parked car. She lets fly with a run-on, impassioned tirade of vulgar obscenities that exactly suggests the wild emotion of a mongrel straining at the end of its leash.

In another sequence Sylvia becomes attracted to a macho male Lab at the dog park and engages in an off-stage love tryst that offers vivid material for audience imagination.

Derek Calibre is also fun to watch in three supporting roles — one of them as Phyllis, an old college friend of the wife's. Dressed up in delightful drag, Calibre makes absurd sense of a woman resigned to her husband's infatuation with a goldfish.