Harbor, the new play by Chad Beguelin at Primary Stages, takes place in Sag Harbor, N.Y., an affluent beachside village on the South Fork of Long Island. But more importantly, it takes place now. That is, right now.

It's worth emphasizing this, partly because Beguelin's script unfolds with such ease and buoyancy that you might forget about the novelty of it. But "Harbor," which is mainly about a gay couple navigating the complexities of married life, wouldn't have made much sense a decade ago, when same-sex activity was still forbidden in several states, or even three years ago, before the New York Legislature extended the right of marriage to all its residents. For that matter, the play wouldn't have felt quite as relevant even this past spring, before the Supreme Court tossed the so-called Defense of Marriage Act into the dustbin of history. Harbor is a creature of the present moment, and because of that, it lands just right.

But enough about that. Beguelin doesn't really have politics on his mind; in fact, Harbor is a fairly old-fashioned comedy about the ever-present tug of family and commitment. The lights rise on Donna, an amiable drifter who shares a van with her teenage daughter Lottie. They've been living there for a while, holding out until Donna can get herself a dream job singing on a cruise ship. They've just pulled into Sag Harbor, where Donna's brother Kevin lives in a gorgeous mansion with his rich husband, Ted. Donna's plan--- to show up unannounced, then slowly ingratiate herself into Ted and Kevin's pristine life, upending it in the process--- goes pretty much as scheduled, until it doesn't.

Things in paradise, of course, are not quite as they seem. The boyishly cute Kevin has been working on a novel for about a decade, living off of Ted's high income as an internationally acclaimed designer. This has not added up to a satisfactory life, though, and with Donna there to remind him of their childhood dreams, he starts to unravel into a haze of alcohol and self-doubt. Ted, meanwhile, takes up the bookish Lottie as his personal improvement project, even as she persists in her obsessive quest to find her biological father. Funny and honest encounters abound during Donna and Lottie's overextended stay, and it all culminates in some surprising twists.

Randy Harrison, of Queer as Folk fame, glides effortlessly through the role of Kevin, a guy who's relied on his innocent charm too long and knows it. Erin Cummings perfectly radiates the earth-bound cunningness of Donna, and Alexis Molnar easily embodies the adolescent Lottie's beyond-her-years disenchantment. Paul Anthony Stewart, as the sort-of patriarch Ted, hits all the right notes of exasperation and concern that mark his character's journey.

I'll confess one note of dissatisfaction with Harbor: I want a sequel. The play's ending doesn't answer many questions about the ultimate destiny of these four people, and in fact it suggests that far bigger challenges lie ahead. Perhaps Beguelin is planning a chronicle in the style of Tales of the City, with a whole set of serialized dispatches from the Sag Harbor house coming out regularly. I, for one, hope so.