It's a mistake that's quickly brushed aside. But the slip-ups soon begin piling up in this 80-minute gem of a play until what's real and what's not collapse in a heap. It's confusing and thrilling stuff.

"I'm having a hard time figuring out where I am," our heroine, dementia expert Dr. Juliana Smithton, says meekly at the end.

For much of the play, which opened Thursday at the Samuel J. Friedman Theatre, we know the feeling — White is stingy with his clues.

Among the questions swirling about: Who is lying? Is the good doctor getting divorced? What happened to the couples' daughter? Who is the woman in a yellow bikini who sparked Smithton's meltdown? And, ultimately, what is wrong with our heroine? Something definitely is, since her command of English slowly betrays her, with "thingy" creeping in and exasperated references to "the other place," her Cape Cod summer home.

The play — so buffed and polished it now seems to squeak — is matched by a searing, brilliant performance by Laurie Metcalf, who is simply astonishing as she goes from snippy, bossy scientist to a broken, confused intruder wolfing down Chinese food on the floor.

Director Joe Mantello keeps up a blistering pace — snippets of scenes dissolve into another, past and present collide. Speed is important to keep the audience guessing, but it leaves no room for a moment's error. Mantello proves as sharp as the narrator is unreliable.

"The Other Place" had its world premiere off-Broadway at the MCC Theater in March 2011, starring Metcalf and helmed by Mantello. The Manhattan Theatre Club has happily given a rebuffed version a bigger platform with some other supporting actors. It simply gleams.

While Metcalf alternates between playing the narrator and patient, Daniel Stern plays her trying-to-be-stoic oncologist husband, and Zoe Perry portrays the couple's daughter as well as a neurobiologist and another woman dealing with her own crisis. John Schiappa plays a few small roles.

Seeing Metcalf and Perry onstage together as mother and daughter is one of those beautiful things that come around too infrequently. The two are in real life mother and daughter, and Perry is every bit as wonderful as her mom in a touching final scene in which the roles of child and mother are reversed.

William Cusick's projections are wistful and gloomy — seeping darkness often fills the back wall — and Fitz Patton's soundscape, which alternates from scratchy telephone calls to barely tolerable electronica, is spot on.

The single, spare set by Eugene Lee and Edward Pierce, which consists of interlocking wood frames, seems to reach for a Piet Mondrian vibe but ends up looking too much like a bunch of old lobster pots nailed together.

Though the play is just over an hour long, Metcalf works the hardest and longest, never leaving the limelight. As the audience enters, she's in a fancy chair in the middle of the stage, legs crossed, picking at a smartphone or staring into space. It's her only moment of calm before a stunning, frantic and moving piece of theater.

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Online: http://www.manhattantheatreclub.com

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Follow Mark Kennedy on Twitter at http://twitter.com/KennedyTwits