I wouldn't go so far as to say you don't revive "The Philadelphia Story" unless you've got a young Katharine Hepburn to play Tracy Lord. Young Katharine Hepburns just don't come along all that often, and you shouldn't penalize Philip Barry's elegant comedy of manners for lapses in the evolutionary process.

But I will suggest that if you don't have a performer with a similarly distinct stage personality, you're in a fair amount of trouble. To describe Tracy as the sun, around which revolve all of Barry's articulate characters, is to betray their prevailing view of her as a silvery, distant goddess. Call her the moon in a glittery night sky. One thing is certain: Her waxing and waning moods very much govern the behavior of the adoring men in her life.

At Arena Stage, the role that rekindled Hepburn's star (first on Broadway in 1939, and then in Hollywood a year later), has fallen to Laila Robins. While it may seem ungentlemanly to blame her for what amounts to a lackluster revival, she, indeed, is chief culprit. Tracy Lord is the best of her breed, and Robins is merely a functioning actress. Hard as the supporting players may work, witty as some of them may be, there is a notable absence of magnificence at the center of this production.

The word is not mine. It comes from the mouth of Mike Connor (Casey Biggs), the tough-guy reporter from Destiny Magazine, who's come to sniff out the dirt on Tracy Lord on the eve of her second marriage and ends up hopelessly intoxicated by her special perfume. "There's magnificence in you, Tracy," he's soon babbling in flagrant disregard of all his proletarian biases, ". . . a magnificence that comes out of your eyes, that's in your voice, in the way you stand there, in the way you walk. You're lit from within, bright, bright, bright."

That's not just the champagne talking. It's the crux of the whole play, which wants to chart the awakening of the "golden girl" inside the cool, classy socialite. If we can't see what Connor sees -- a very special woman under the Main Line manners -- Barry's bountiful badinage is apt to register as so much empty frivolity. The plot may be gossamer, but we've still got to care whether Tracy marries priggish George Kittredge (Tom Hewitt) or wakes up in time to go back to her first husband, Dexter Haven (John Leonard), who once made the mistake of popping her in the jaw but otherwise is suave and understanding. You'll care, however, only if you care about Tracy.

Robins, mind you, is not going to get hooted off the stage. She is a striking woman, with a fine aquiline profile, bewitching eyes and a svelte body. Her voice is not without musicality. And frankly, she looks sensational in pants. But you get the impression that she's reaching for the role; there's nothing remotely instinctive about the performance. All of the character's ingrained traits -- her superiority, her high-born ease, her independent charm -- seem, in Robins' case, to have been acquired with considerable effort. In a Barry comedy, a show of effort is no more appropriate than a fly in the punch bowl.

Elsewhere, the production, directed by Douglas C. Wager, is in better shape (although that may be akin to touting the merits of a used car by boasting that, except for the motor, it's in mint condition). Still, Biggs combines two seemingly contradictory qualities -- the roughness of a young James Cagney and a Boy Scout's bashfulness -- to make the snooping reporter appealing to have around. Henry Strozier reinvents the role of the eccentric uncle with great warmth and originality. And there's a delicious contribution by Heather Ehlers, whose performance as Tracy's giddy kid sister amounts to a virtual treatise on the agonies of adolescence.

Leonard may seem a little too wet behind the ears to handle so grand a filly as Tracy (were Tracy as grand as she's said to be), but he's clearly preferable to Hewitt, who sweats under the collar. So the basic dramatic equation is not thrown out of kilter. Cary Anne Spear, as an inquiring photographer, serves up her wisecracks on wry. And Halo Wines and Terrence Currier have the proper upper-crust airs as Tracy's parents, even if their evening clothes aren't all that flattering. But their collective labors are not enough to overcome the nagging sensation that Arena's playing dress-up games on us.

What makes "The Philadelphia Story" so hard to pull off is that it profiles a society of blue bloods for whom a life of privilege is a given. They have the right family trees; their money has aged in the right banks; socially, they were born with perfect pitch. No more than a king thinks of himself as kingly do Barry's aristocrats view themselves as aristocratic. They simply are -- and any display of credentials is regarded as unseemly.

If you force the characters, they look aloof and overbearing. Underplay them and they lose their uniqueness, which is their unwavering conviction that they are the happily well-bred few. It's what you might call an attitude problem, and I'm not sure Arena's licked it. Wager, in fact, seems vaguely intimidated by the play; the higher the comedy gets, the less comfortable he is with it. What he ends up showing us is a middle-class view of the upper classes.

Indicatively, quite the nicest bit of business he has concocted has nothing to do with Tracy and her beaux. It's late night in the formal garden. The maid and the butler are picking up champagne glasses, and the night watchman is making his rounds. The sprightly strains of a society orchestra are wafting through the French doors. Suddenly, all three employes find themselves lumbering the light fantastic.

The improvised pas de trois makes for as charming a moment as any in the production. Strange, though, that it should come from the help, when you consider that Barry has populated the play with so many bona fide charmers. Someone, I suppose, has to do the job.

The Philadelphia Story, by Philip Barry. Directed by Douglas C. Wager; sets, Adrianne Lobel; costumes, Ann Hould-Ward; lighting, Allen Lee Hughes. With Heather Ehlers, Halo Wines, Laila Robins, Thomas Anthony Quinn, Henry Strozier, Cary Anne Spear, Casey Biggs, Tom Hewitt, John Leonard, Terrence Currier. At Arena Stage through April 27.