When invited into the homes of the very rich, one has certain expectations: a peek at the art collection; a little wistful envy over the quality of the surroundings; the hope that the cook will be making dinner. When invited into the homes of the very rich under the guise of theater, the expectations are virtually the same -- an observation that may well have been the launching point for John Guare's Six Degrees of Separation. Written in 1990, the play centers on a privileged couple, Louisa and Flanders Kittredge, whose penthouse is visited by an especially charming confidence man, and who tell their story to an audience that flanks their well-appointed drawing room. Unfortunately, as directed by Patti Bean, Six Degrees finishes off Main Street Theater's ambitious and generally satisfying season with a dull thud.

Best known for his wonderfully sad play The House of Blue Leaves, Guare is the sort of playwright who measures his craft out in tantalizing bits. We are let in on Louisa and Flanders's secret almost immediately: They need $2 million to seal a Japanese art deal, and a possible source of that money, their even richer South African friend Geoffrey, is coming to dinner. It's an honest conflict -- the discomfort in approaching a friend for money, especially for business purposes -- and Louisa is crafted to evoke our sympathy. She's a worrier, and we worry with her. Or, in the case of Main Street's production, we wonder why we aren't worrying with her.

The challenge in doing a realistic play about wealthy people is that the audience has to believe, especially in an intimate setting, that the characters are indeed rich. And that never happens here, in large part due to Chris Wagner's inadequate costume design. Louisa, a woman who quips about great books and the price of a Cezanne, is outfitted in a frumpy red secretary's suit and a dreadful purple ensemble that must have been a bridesmaid's gown. Is it possible to believe that rich people have bad taste? Of course it is, in every instance except here, where issues of taste in art and culture are at the very nexus of the story. Therefore, the embarrassingly fake Kandinsky that hangs upstage is just as jarring as the actors' collection of cheap ties and bad shoes. The notable exception is Jan Brook as Kitty, a friend of Louisa and Flanders's, who appears to have provided her own clothes and jewelry.

Still, such problems can melt away with the right casting. But here too, Bean stumbled. There's nothing happening between Ginny Lang's Louisa and Ron Jones's Flanders. As the charming bad boy, Paul, Joe Okonkwo is fine until he has to make the transition back to his former street self, a transition that lacks any believability. When we should be soaring on Guare's humor and elegant dialogue, we're instead wondering why there's such a stiffness between these actors and so little reason to care what they do with (or to) the intruder in their midst.

There are a few salvaged performances, all in minor roles. As Louisa and Flanders's children, Jentry Brown and Ben Pollock are petulant and snippy in the way the children of privilege so often are -- "I'm going to get married and ruin my life, because it's the only way I can hurt you," Tess screams at her father during a phone conversation. As Tess's friend Trent, Scott Tesh is especially flip and engaging, no doubt having honed his comic ability during his recent long run in Compleat Works of Wm. Shakespear at New Heights Theater.

As with any sturdy play, the resonant themes -- class, race, identity -- float somewhere above the murkiness of the production. What a shame it is to have to stab at them in an attempt to piece together Six Degrees as it floats by in a cheap chiffon frock.

Six Degrees of Separation plays through May 18 at Main Street Theater, 2540 Times Boulevard, 524-6706.