You will not have an easy time wending your way through "M. Butterfly," a new play by David Henry Hwang that opened a four-week, pre-Broadway run at the National Theatre last night. Indeed, on the very simplest terms, it would seem to defy belief.

Here is a drama that wants to tell the story of a French diplomat (John Lithgow), who discovers his fantasy of the perfect Oriental woman in the star performer of a Chinese opera company. For more than two decades, in Beijing and Paris, they pursue an illicit affair. She even presents him with a son.

Then the facts come to light: Over the years, the diplomat has been passing official secrets to the lithe opera star, who is in cahoots with the communist regime. Hold on, there's more: The enigmatic seductress is a man -- among whose greatest performing skills must be counted the ability to hide his true gender even in bed. (The baby was rustled up by Chinese authorities to lend credence to the charade.) But there's even more: Convicted of treason and jailed, the diplomat steadfastly refuses to believe that his Madame Butterfly was really Monsieur Butterfly all along.

Lest you bellow "preposterous!" you should probably know that Hwang has based his play on an actual espionage case that rocked France a couple of years ago. Although the story is no less improbable in its theatrical guise, "M. Butterfly" can at least lay claim to some moments of visual beauty and a provocative thought or two about the way East and West willfully misunderstand each other.

Little of this is rendered realistically. Instead, Hwang relies heavily on first-person narration. Most of it is delivered by the diplomat, who informs the audience about his past, his obsessions, his "ruthless climb to the bottom." Later on, the opera singer (B.D. Wong) steps front and center to let us in on his ruses and their underlying psychology. Periodically the narration gives way to individual scenes, which are enacted with all the exotic trappings of the Peking Opera.

On a blood-red set that resembles the inside of a giant snail's shell, hooded prop men scurry about, attending efficiently to the actors' needs. Latticework panels glide on and off the stage. Gongs reverberate. And great painted curtains flutter to the floor, signaling sudden leaps forward in time and place.

There is a further complication to what may strike you as complicated enough already: Hwang's decision to play his strange love story against bits and pieces from Puccini's "Madama Butterfly." That opera, Hwang believes, incorporates a lot of the dangerous misconceptions that the West has long entertained about the seemingly weak and submissive East. It is certainly central to the delusions of the diplomat, who believes he has at last been blessed with a pliant and dutiful mistress -- one who will love him unconditionally, however loutishly he behaves.

You can be forgiven for scratching your head now and then and asking yourself on just what level Hwang is operating. "M. Butterfly" tantalizes by promising to explore a decidedly bizarre relationship. But it ends up devoting entirely too much attention to footnotes, ironic asides and running commentary on such issues as male sexuality and how America lost the Vietnam war (related topics in Hwang's view).

In the process, some fundamental questions go unanswered. Just what secrets did the diplomat betray? How did he get caught? Was he merely the hapless victim of an astounding scheme or did he, in fact, realize deep down that he was involved in a masquerade and choose to embrace it anyway? Hwang seems far more concerned with the symbolic aspects of the saga. But if the diplomat is not to appear a laughable dolt, "the patron saint of the socially inept," as he calls himself, we need to know a lot that Hwang isn't telling us.

One can see why director John Dexter was attracted to the material. He is the man who staged "Equus," which delved into the behavior of a sexually aberrant stableboy and discovered in him a primitive passion that served to indict our passionless age. "M. Butterfly" wants to capture a similarly blinding passion, but Hwang's net is riddled with holes and the elusive prey flutters forever out of reach. I can't say the sumptuous production that Dexter has orchestrated (with a considerable assist from designer Eiko Ishioka) helps matters. Theatrical as it is, the production, like the play, keeps distracting us with peripheral effects.

Both Lithgow and Wong have the occasion to sit at an onstage makeup table and change identities before our very eyes. There is a primal fascination to the ritual, the external transformation serving to mark a mutation deep in the characters' souls. Only afterward do you realize that Hwang hasn't really dramatized that change. A theatrical convention has conveniently ushered us over a critical hump in the play's fortunes.

In the subsidiary characters, the deficiencies are even more apparent. Lori Tan Chinn, looking like a water rat in a Mao suit, may be an amusing embodiment of Communist Party officiousness, but she appears to have sprung from a Disney cartoon. The diplomat's wife (Rose Gregorio) would be more at home in a kitchen-sink drama, set in Brooklyn. And while the voluptuous Lindsay Frost appears in three different roles, her principal function in all three seems to be to bare her ample curves.

Lithgow is saddled with a near-impossible assignment -- making us care for a man who risks registering as either silly or demented. Lithgow tends to favor a kind of eye-rolling intensity as a way out of the fix, and he succeeds in holding ridicule at bay. But for all the explanatory talk the character indulges in, the diplomat remains an unplumbed enigma.

Wrapped in a dazzling wardrobe of silks and crowned with a succession of flower-strewn wigs, Wong is the sort of self-dramatizing temptress Hollywood appreciated in the 1940s. The husky-voiced actor is credible enough as a woman, but he doesn't convey the extra charge of eroticism that might ignite his scenes with the diplomat. When in the end he reverts to male attire, he comes across as a petty opportunist, not as the gifted manipulator he purports to be.

But then he, too, is battling great odds and repartee that often soars no higher than this: "I am your fantasy." "You? You are as real as hamburger." Hwang's slangy dialogue is clearly at war with the dark poetry he perceives in the tale.

This is as curious -- dare I say "dis-orienting" -- a play as you will see this season. But all it ends up proving is the age-old dictum about fact being stranger than fiction. Watching "M. Butterfly," you continually tell yourself it could never happen. And yet, apparently, it did.

M. Butterfly, by David Henry Hwang. Directed by John Dexter. Sets and costumes by Eiko Ishioka; lighting, Andy Phillips; Peking Opera consultants, Jamie H.J. Guan and Michele Ehlers. With John Lithgow, John Getz, Rose Gregorio, George N. Martin, Lindsay Frost, Lori Tan Chinn, Jamie H.J. Guan, Alec Mapa, B.D. Wong. At the National Theatre through March 6.