Light’s touch lifts ‘Children’

And, as played by Judith Light, she’s the main reason to see the Williamstown Theatre Festival’s meticulous production of this early foray into the field that would become Gurney’s life work: the entomology of the American WASP.

The play takes place entirely on the hydrangea-bedecked terrace of a classic shingled beach house, located on an unnamed island off the coast of Massachusetts. The characters play tennis, drink, swim, and wrangle over real estate. In short, it’s a regular upper-class fiesta - set, appropriately enough for the characters’ various struggles for independence, on the Fourth of July.

All of the elements are in place for a biting dissection of the particular tiny slice of American society that fascinates Gurney, and there are moments when he finds real and painful truths. Too often, though, the themes are baldly stated, and the characters are endlessly explaining who they are and how they feel.

As even the young playwright must have known, no WASPs would ever say so much to one another; they’d simply express it all by how they stirred the Bloody Marys or tossed the ball. But it would take Gurney a while to learn how to write such characters without having them explain themselves to us, so in “Children’’ we’re too often left listening to a description instead of watching a play.

Fortunately for Williamstown, however (and for the co-producing Westport Country Playhouse, where “Children’’ ran before moving north), Light knows exactly how to tell the story without telling everything. Just watch as she announces to two of her grown children that the third, an estranged brother known as Pokey, has called to say that he’s surprising them with a holiday visit.

“Of course I’m delighted,’’ she says. “I’m thrilled. We’ll all be together for the Fourth. What fun.’’ Without a script in hand, it’s impossible to know how Gurney punctuated those words - but Light punctuates them with an absolutely gracious yet utterly cool inflection, conveying every nuance of dismay, surprise, and anger while still maintaining complete control. If that’s not a true WASP, what is?

Mary Bacon, as the daughter-in-law whom Mother clearly sees as her natural successor in the role of matriarch, finds a similarly delicate balance between finely suppressed despair and outward perkiness. She begins as the model of headband-wearing good cheer, then slowly unravels to reveal her terror at turning into exactly the woman she was always brought up to be.

As the recently divorced daughter who’s secretly carrying on with the family’s former yard man (now a successful contractor), Katie Finneran has a tricky role: We need to see both her rebellion and her fear of rebelling, and Finneran stays poised on the edge. But James Waterston, as the most traditional sibling, starts out too explosively angry for the part. He needs to build slowly to the violent outburst that climaxes the play, but instead he’s already unhinged from his first moment onstage.

All the characters, though, are put at a disadvantage by being endlessly compared to the one we never see (except in shadow near the end), the turbulent, disruptive, charismatic Pokey. He’s married a Jewish woman (gasp!) who gives their children Coke at meals (unspeakable!) and he’s not interested in inheriting the house (the horror!). Everyone else is so fascinated by him that, inevitably, we begin to find him a little tiresome. And because he’s the one who gets the plot moving, his persistent absence from the stage comes to feel distractingly forced.

Well, that’s how we know it’s an early play. But Light - along with the lovely, note-perfect set by James Noone, which shades from dawn’s early light to the twilight’s last gleaming with subtle beauty, thanks to Rui Rita’s lighting - makes its 90-plus minutes pass more gracefully than they otherwise would. This Mother may never reveal her name, but as we watch her manage, manipulate, and ultimately emancipate her children (and even, perhaps, herself), we come to know exactly who she is.

Louise Kennedy can be reached at kennedy@globe.com.