Pirandello's "Enrico IV" is a fun house for the mind. Nothing is quite as it seems to be. It takes place in a great stone villa in present-day Italy, but the rooms have been made over to resemble the regal quarters of Enrico IV, the Holy Roman Emperor who ruled during the 11th century.

We don't know exactly who the central character is -- a flamboyant playboy, maybe. Twenty years ago, in the course of a lavish masquerade for which he disguised himself as Enrico IV, he tumbled from a horse. When he regained consciousness, he believed he was the real Enrico IV. Ever since, his entourage has humored him -- dressing up in period costumes, speaking of historical incidents as if they had just transpired and making sure that the electric lights are off whenever he surges through a room.

But there's more to it than that, as you will quickly conclude at Arena's Kreeger Theater, where Pirandello's 1922 play opened last night. Madness is a relative state. The lunatic can sometimes be the most lucid of human beings; fiction can be truer than fact; and the role-players are not necessarily those wearing heavy rouge and flowing robes.

Long before Eric Berne revealed the "Games People Play" and the weekly visit to the shrink became an American habit, Pirandello was exploring the labyrinth of human identity. "It's a fascinating case. Study me carefully," says Enrico IV, not without a certain boastfulness, to the doctor who has been summoned to the villa. The doctor, along with some of the participants in that long-ago masquerade, hopes to jolt Enrico IV back into the 20th century by reenacting fatal events from the past. They are entering dangerous territory.

Indeed, although Douglas Stein's set is made of massive pillars and solid-oak doors, you get the impression that the floor tilts off in odd directions, as it does in a fun house. The walls are not hung with distorting mirrors, but they could be. People and events keep changing shape in this kingdom, and everyone seems stuck in a different time zone.

The equation is complex to begin with. Then Pirandello adds yet another layer: What if Enrico IV were not mad but merely pretending to be mad? What if his overheated folly were cold revenge in disguise and his retreat to the 11th century a willful rejection of the hollow present?

"Enrico IV" is very much drama as Rubik's cube. Watching it requires a fair amount of patience and application. Pirandello is often accused by his detractors of being dry and overly cerebral, but I don't think that's it. His plays are deeply felt, written out of a profound torment.

It is, however, not easy to get at the source of his characters' passions. For much of the evening, we are preoccupied with cutting through mounds of exposition, figuring out who's who and peeling away illusions that are doubly difficult to penetrate because the characters hold onto them so tenaciously. First and foremost, "Enrico IV" forces you to be a detective -- watchful, wary, uncommitted. Only when the details start linking up does the play begin to make a claim on your emotions. Still, I suspect it's a work best savored once it's over, as opposed to a drama that implicates you as it unfolds.

Directors Zelda Fichandler and Mel Shapiro have a keen awareness of Pirandello's sly wit (which he often directed at the pompous omniscience of psychiatrists) and his biting intelligence. Although the play has the sweep of a cockamamie pageant, the liveliest action is mental, and the directors have clearly spent considerable effort distilling thoughts, honing meanings and polishing ambiguities.

That's not wasted effort. Pirandello's characters are nothing if not calculating. Yet the production as a whole seems rather too manipulative for its own best interests. We seem to be witnessing a carefully controlled experiment rather than a spontaneous outbreak of psychological warfare.

As Enrico IV, Stanley Anderson is, by turns, tyrannical, childlike, incisive as steel and elusive as a remembered dream. Anderson is very adroit at mixing it up. With age, his face has lost its hardness and acquired a doughy corpulence that seems to have expanded his range of expression. One minute, he can look like a puffy, rouged-up fop; the next, like a fallen choirboy. It's as if he's remolding himself on the spot -- a Pirandellian notion if ever there was one.

Good, too, is Halo Wines, as the fiance'e who scorned him many years ago and now has come back to help with his cure. Wines always has been adept at playing shrews, bullies and vulgarians. But in recent seasons, she's added aristocratic colors to her palette. Here, she has the faded elegance of a pretty woman who now doubts her charms and whose nerves are beginning to betray her. There's more than a touch of an neurasthenic Antonioni movie heroine to the performance.

As her lover -- and Enrico's nemesis -- Frank Maraden is a curious mixture of whimsy and intrigue, which, combined with his looks, gives him the allure of a rather tall, gray-haired leprechaun. It's an image I would have preferred not to entertain, but Maraden's little, lighter-than-air leaps don't do much to discourage it.

Henry Strozier, however, is properly self satisfied, as the goateed doctor who throws around such terms as "analogical elasticity" as if they actually signified something. And David Ingram bumbles amusingly as a new employee in the villa, struggling to keep up with the charade.

They're all toying with dynamite. As Enrico explains in one of the play's most telling speeches, the madman takes all our rational assumptions about life and behavior and shakes them vigorously until the logic falls out. Reality is reduced to rubble. Everything, which is to say nothing, becomes believable. And the mind, suddenly unanchored, floats in a void.

Enrico IV finds a horrible way to lock himself back up in the fictions of the past -- this time forever. The rest of the characters, Pirandello indicates, are left with despair and emptiness. And that includes us.

Enrico IV, by Luigi Pirandello. English version by Ralph Cornthwaite. Directed by Mel Shapiro and Zelda Fichandler. Sets, Douglas Stein; costumes, Marjorie Slaiman; lighting, Allen Lee Hughes. With David Marks, Michael Wells, Steven Major West, David Ingram, Bob Kirsh, Marissa Copeland, Frank Maraden, Henry Strozier, Halo Wines and Stanley Anderson. At Arena's Kreeger Theater, through Feb. 21.