NEW YORK -- John Guare's tricky and tantalizing new play, "Six Degrees of Separation" (at the Mitzi E. Newhouse), takes its title from the notion that any two individuals -- say, the president of the United States and an Italian gondolier -- are separated by only six people.

Here's how it might work: The president knows someone, who is related to someone, who went to school with someone, who now dates someone, who, while on vacation, struck up a friendship with someone, who lives next door to someone, who knows the gondolier.

Ouisa Kittredge (Stockard Channing), the wife of a prosperous New York art dealer and the moral center of Guare's play, is highly taken with this prospect. "I am bound to everyone on the planet by a trail of six people," she marvels -- the vision of global togetherness warming her heart. Then a wrinkle ruffles her brow and she realizes the catch: You've got to find the right six people.

Otherwise the trail goes cold, the chain is broken and the cozy world isn't so cozy after all.

That's what happens in "Six Degrees of Separation," which breezes along entertainingly for most of its 90 minutes, then suddenly plunges into a terrible sorrow, taking the audience with it. Guare has always been interested in the drunken, roundabout ways of destiny, which gives his plays ("The House of Blue Leaves," "Landscape of the Body," "Lydie Breeze") a loopy originality. "Six Degrees" doesn't lack for wackiness, but its odd pieces come together with a precision and ease not always evident in his earlier works.

Fresh from a mugging in Central Park and bleeding from a knife wound, a young black man (James McDaniel) bursts into the posh apartment of Ouisa and her husband, Flan (John Cunningham). They are properly aghast, as is their dinner guest, a white South African millionaire. But when the intruder explains that he is Paul Poitier -- son of the actor, Sidney -- and that he went to Harvard with their children, they relax their suspicions.

By the time Paul has propounded his theory of "The Catcher in the Rye" (it has served, he believes, as a guidebook for presidential assassins), prepared pasta for everyone and cleaned up the kitchen, they are captivated. However, it's his promise to wangle them all parts as extras in the movie version of "Cats," which his father is about to film, that turns them to putty in his hands.

Ouisa and Flan advance him $50, put him in the extra bedroom for the night and all but make him an honorary family member. When they discover that he has spent most of the night with a male hustler, the hospitality is hastily retracted and it occurs to them that maybe this Paul Poitier isn't who he says he is.

As they try to track down the truth, the focus widens to include the president of a foundation and his barking wife, a Jewish obstetrician, a clutch of ungrateful progeny and an aspiring actor from Utah, who loses his innocence on the dance floor at the Rainbow Room. Guare neatly weaves their destinies together -- all the while keeping Paul's identity just out of their reach (and ours) -- which gives the play the breathless extravagance of a wild-goose chase.

If it were only that, "Six Degrees" would be a clever update on the theater's eternal preoccupation with dupes and dupers. But there's more to Guare's trickery. Just about everything in the play is two-faced, starting with the Kandinsky painting that revolves overhead, revealing a different design on each side. Language willingly lends itself to the confusions, and even so obvious a phrase as "striking coal miners" is open to interpretation. (Ouisa admits she always understood it to mean "chic" coal miners.)

Paul is the nominal con man here, a creature of multiple personalities. But his well-heeled victims are no less duplicitous. Their scams just happen to involve Cezannes and Matisses and millions of dollars whizzing under the table. Only Ouisa's awakening in the end signals a way out of the moral chaos. She alone believes Paul's last-minute cries for help and is willing to trust him all over again, until fate intervenes and permanently severs the connection -- a phone connection, this time. Ouisa is left bereft.

Channing's performance is dazzling. She has the dizzy gaiety of the hostess who won't let on that the party is going badly. Then it's no longer the party but life that is going poorly and Channing has made the transition without your realizing it. McDaniel projects by turns the propriety of the Ivy League, the sullenness of mean streets and the innocence of a kindergarten, thereby making Paul a rich enigma.

In the cast of 17, there isn't a performance that isn't right to the point, although some of the roles are mere cameos. Director Jerry Zaks is an acknowledged master at orchestrating farce, and he navigates Guare's hairpin turns with aplomb. But he also sees to it that the sadness in this fable is heard, and never so much as when the bewildered hayseed from Utah (Paul McCrane) tells us how Paul robbed him of his money, his virginity and finally his very sense of self.

Guare took the premise of his play and a fair number of its details from a real-life incident that occurred in New York in 1983 and was reported on the front page of the New York Times. I seem to recall at the time that the article made for great cocktail party chatter and provoked snorts of laughter at the expense of sophisticated New Yorkers, who fell for the imitation Poitier. "Six Degrees of Separation" doesn't spare the laughter, but it uses the outlandish escapade to probe an age that thrives on gossip and chicanery.

"How," Ouisa asks, once the dust has settled and Paul has vanished, "do we keep what happens to us without turning it into an anecdote? ... How do we keep the experience?" To a large degree, Guare's play itself is the answer. Art is how we fix stories that would otherwise get devalued in the common retelling.

'Taming of the Shrew'

Tracey Ullman in gingham and Morgan Freeman in chaps are the draw for the New York Shakespeare Festival's production of "The Taming of the Shrew," currently at the Delacorte Theater in Central Park. Director A.J. Antoon has relocated the action in the American Wild West, where the buffaloes roam, the tumbleweeds tumble and the accents twang like so many broken guitar strings.

In theory, I suppose there's no reason Kate (Ullman) can't pack a pistol or Petruchio (Freeman) can't truss her up with a lasso. But at the preview performance I saw, the shenanigans were as broad as the proverbial barn door -- pieces of which also seem to have gone into the making of John Lee Beatty's back lot set.

Ullman can throw a great raging tantrum. Freeman swaggers affably. And Arena Stage's Mark Hammer, stroking an abundance of white whiskers and smacking his gums, reels about the premises as the aging suitor Gremio. It's all cartoon Shakespeare -- "yippee yi ay" time in old Padua -- and not to be taken seriously for an instant.

Six Degrees of Separation, by John Guare. Directed by Jerry Zaks. Sets, Tony Walton; costumes, William Ivey Long; lighting, Paul Gallo. With Stockard Channing, John Cunningham, James McDaniel, Kelly Bishop, Peter Maloney, Stephen Pearlman, Paul McCrane. At the Mitzi E. Newhouse Theater at Lincoln Center.

The Taming of the Shrew, by William Shakespeare. Directed by A. J. Antoon. Set, John Lee Beatty; costumes, Lindsay W. Davis; lighting, Peter Kaczorowski. With Morgan Freeman, Tracey Ullman, Helen Hunt, Mark Hammer, Tom Mardirosian, Graham Winton, Robert Joy. At the Delacorte Theater, through July 22.