Why is Pittsburgh Irish & Classical Theatre doing a play by David Mamet? What about "Boston Marriage" qualifies it as a Mamet play, other than the fact of his authorship? And what does any of it have to do with Boston?

Suellen Fitzsimmons Derdriu Ring, left, and Melanie Dreyer star in Pittsburgh Irish & Classical Theatre's production of "Boston Marriage." Click photo for larger image. 'Boston Marriage' Where: Pittsburgh Irish & Classical Theatre at Henry Heymann Theatre, Stephen Foster Memorial, Oakland. When: Through July 29. 8 p.m. Wed.-Sat.; 2 p.m. Sun.; also 7 p.m. July 9 and 11; and 2 p.m. July 29 (no performance July 16). Tickets: $26-$36; 412-394-3353 or www.proartstickets.org.

But before addressing those puzzles, let's establish that the result is downright delicious. "Boston Marriage" is a sparkling bauble, a period comedy of witty, highly charged sexual negotiation, carried out in lavish repartee between two lesbian lovers, with a wild card provided by a third, a young maid who might turn out to go either way or perhaps just back to her native Scotland.

Set at the turn of the 20th century, the dialogue is very arch, an intoxicating, self-conscious verbal gymnastics, sort of like Henry James or Edith Wharton on speed, which is to say, very much like Oscar Wilde, complete with the occasional epigram.

"Men, what can you do with them?" one lady asks. "Just the one thing," the other replies. As we laugh, I suppose it's sex we imagine, but men are also good for money, because, as the ladies agree, they "live but to be deceived."

The dialogue is also like Wilde in its erotic titillation, here raised from subtext to conscious subject, as the two mature women, the older Anna and younger Claire, deal with major threats to their long relationship: Anna's capture of a rich married man as her financial protector and Claire's sudden passion for a young woman she hopes, with Anna's help, to seduce.

Their blandishments and ultimatums, avowals and recriminations are all couched in a flowery, decorous language seemingly lifted from the diary of a precocious debutante (Wilde's Cecily, perhaps) or the lurid pages of a three-volume novel.

That's Mamet's basic joke: the contrast between this artificial literary language and the passions it bedecks, further sharpened by modern interjections like "tell it to the Marines," "choke a horse" or "put a sock in it." Anna even accuses Claire of proposing to use her as her beard.

Then at the end of Act 1, there's a turn and counter-turn, as the two ladies' amatory/financial adventures suddenly intertwine with disastrous implications. And in Act 2, they come up with a hare-brained scheme, as silly as anyone could wish.

"Boston Marriage" is like champagne, with plenty of bubbles to tickle the palate. Or perhaps it is more like asti (very) spumante, which is to say a shade sweet.

Director Jeffrey Cordell supervises with restrained zest. Gianni Downs provides a gorgeous box set (a good trick in the intimate thrust space of the Heyman Theatre), decorated with high Aubrey Beardsley yellow and light green coloring with good Persian rugs and elegant furniture, prettily lit by Erick Leininger. Pei-Chi Su's lovely costumes, especially for Anna (and what lovely hair), suggest that the male protector is very generous.

All depends on the three actors, who are very well cast. Melanie Dreyer has the most demanding role as Anna, the handsome queen bee. She may occasionally be overly arch, but with such elaborate language, who can say? And beneath her verbal skills, we see her fears.

Derdriu Ring's Claire often gets to play the practical deflator, and she does it very well, with a natural crispness, though I'm not sure I entirely believe her erotic infatuation.

Karen Baum is perfection as the maid, with her sweet face expressive in deadpan or scrunching up into a grimace. And you'd cast her for her voice, alone, with its dynamite lower register.

How shrewd is this maid? What role will she play? How will Anna and Claire resolve their amours? Naturally Mamet saves one final twist for the last.

On the one hand, I didn't want it to end. On the other, it feels a couple of minutes too long, those minutes coming about three-fourths of the way through. On the third, with less than 90 minutes of playing time, why take an intermission?

So, what makes this Mamet? Perhaps it's because, beneath the badinage, you feel love, desire, possessiveness and loneliness at work. It's just talk, but it feels like huge armies prancing and wheeling, scheming all the while. That's Mamet, the way his language both hides and reveals.

And Boston? Yes, "Boston marriage" is the label for a settled female relationship (whether sexual or not). But the play teasingly begins with an off-stage song in which the ladies brag of "a Boston marriage in Grammercy Park" (presumably not exactly the Grammercy Park of Henry James). The play's program, however, specifies "a New England city."

In truth, "Boston Marriage" inhabits an invented place and also time, somewhere at the conjunction of classic literature, period decor and modern psychology. It is part parody, part homage. If a reason be needed, that's why it's at PICT, because the period and the polish give it a classic feel, like a witty post-modern take on a lost original.