"Talley's Folly," at the Round House Theatre in Silver Spring, is an evening to gladden the heart.

Tiny in scope, it is nonetheless large in spirit. Detailing a night of summer courtship in a dilapidated Victorian boathouse in rural Missouri back in 1944, playwright Lanford Wilson succeeds in convincing us anew of that age-old saw: for every Jack, there is a Jill. But this two-character chronicle is utterly free of sentimental goo. If romance triumphs in "Talley's Folly," it is through dogged perseverance and the painful unveiling of some long-buried truths.

Borrowing Stanley Anderson from Arena Stage and drawing on Greta Lambert from its own resident company, the Round House has a well-nigh perfect cast to play the reluctant couple in the making. Wonderfully appealing performers in their own right, they constitute an irresistible pair. While he resembles a burly teddy bear in an ill-fitting suit, and she is the epitome of the Midwestern spinster teetering on middle age, you will come to think of both of them as beautiful creatures. Unadorned humanity, when rendered as generously as it is in this production, has a way of accomplishing miracles far beyond the reach of Max Factor.

For those who saw the Studio Theatre's superlative production of "The Fifth of July" recently (decidedly, Wilson is having his day in Washington), "Talley's Folly" offers further rewards. The eccentric Aunt Sally in "Fifth of July," who was carrying her husband's ashes around in a candy box, just waiting for an auspicious moment to scatter them over the land, is a latter-day version of the 31-year-old Sally Talley of "Talley's Folly." And the defunct Matt is here very much alive and sworn to win her hand.

"This should be a waltz," he says in a welcoming speech to the audience, "one-two-three, one-two-three; a no-holds-barred romantic story." A hesitation waltz would be a more accurate description. Matt and Sally may be made for one another, but she needs a lot of convincing first. She is, in fact, frankly put out when she returns home late one afternoon from her job as a nurse at the hospital and discovers the 42-year-old Jewish accountant lurking in the boathouse. Her family disapproves of him--disapproves of her, for that matter. He's certainly a strange, shaggy creature, with a displaced childhood somewhere back in Central Europe. And besides, who would want to love her--a plain Missouri girl, whose noncomformist ideas seem merely crazy in the small town?

As the sun sets, the fireflies come out and, across the river, a band strikes up some sprightly Fourth of July music, the courtship proceeds. She is wearing a new dress, after all, and that gives Matt hope each time Sally retreats behind some deep-seated reservation. There are a few slips and spills, as there are whenever two people are learning to dance together. But by the end they are facing one another with stars in their eyes, because they have confronted their respective demons and exorcised them.

Adroitly using the leftover objects in the boathouse--a dusty pair of skates, a lantern, a rotting rowboat--director Jeffrey B. Davis has choreographed the evening's encounter with variety and humor. Unlike so many recent two-character offerings, this one never seems less than full to the brim. The play has clearly been dissected for every passing subtlety and then put together again, fresh as a breeze.

Anderson has always been a remarkable actor, but it occurred to me during "Talley's Folly" that one of the hallmarks of his talent is that he not only gives us a specific character in the here and now, but also manages to suggest what that character was as a younger man, as a boy even. Certainly that was the case with his portrayal of the curmudgeonly Dodge in Arena's "Buried Child," a classic illustration of an old man becoming in his senility the petulant child he once was. You'll see a similar phenomenon at work at the Round House--moments when the bumbling middle-aged accountant glows like an adolescent on his first date.

Lambert, lacking only the vocal power to do full justice to Sally's last-gasp protestations, is splendid at portraying the tug of war going on inside a woman who can't quite bring herself to embrace the one thing she wants most in life. Hiding behind irony, casting slyly amused glances at her unlikely suitor, summoning up arguments with the secret desire that they will be batted down, she is vulnerability itself, pretending to be armor-plated.

Richard H. Young has designed the evocative boathouse slowly giving up its ornate decoration the way an old valentine relinquishes its lace, and he has lighted it with a full appreciation of the magic that dusk can bestow on the humblest locale. For her part, Rosemary Pardee-Holz has found just the right clothes for these characters to wear on a hot July night. The result is a production of effortless achievement and undiluted pleasure. You may not see better all summer.

TALLEY'S FOLLY. By Lanford Wilson. Directed by Jeffrey B. Davis. Sets and lighting, Richard H. Young; costumes, Rosemary Pardee-Holz; properties, Kathleen Wolfrey. With Stanley Anderson and Greta Lambert. At the Round House through July 31.