The funniest scene in "The Other Place" is also its dearest. It involves a vacation house on Cape Cod where a hungry visitor (played exquisitely by Linda Kelsey) and an unwitting, emotionally exhausted host (the sharp Joy Dolo) interact over some anxious minutes. As the righteously sure guest and the surprised homeowner negotiate slippery psychological terrain, the action goes from dangerous misunderstanding to fraught comedy before finally settling into sympathetic acceptance.

The laugh-out-loud-funny scene is clear and tangible in a play where getting a grasp on reality is like trying to cup light in your hands. Such is the slipperiness of truth in Sharr White's illusory 80-minute one-act, which opened over the weekend in a delicate and astute production directed by Aditi Kapil at Park Square Theatre. Most of the action seems like a projection from the mind of one Juliana Smithton.

Smithton, played by Kelsey, is a brilliant neuroscientist who is simultaneously on the verge of a breakthrough and a breakdown. Through her research, she has discovered a miracle drug and is presenting it at a conference in St. Thomas, Virgin Islands. Meanwhile, her family life is in free-fall as husband Ian, also a doctor (James A. Williams), files for divorce and her estranged daughter, who has eloped, makes brief, cryptic phone calls.

White's slight slice-of-life play illustrates the fragility of the mind and consciousness, especially as age or illness starts to affect our wiring and, consequently, our perceptions. Scenes switch quickly, a structure that follows Smithton's thoughts and emotions. The action moves seamlessly, thanks to Michael Kittel's lighting and Kristin Ellert's projections, from lecture hall to home, and from order and strength to confusion and chaos.

Smithton, a role played on Broadway by Laurie Metcalf of "Roseanne" fame, is a showcase part — the sun around whom all the characters orbit.

Kelsey invests Smithton with vigor, brittleness and a touch of cruelty. In admirable quicksilver turns, she credibly veers between being a callous force of nature who, when making a speech, singles out a bikini-clad audience member for uncalled-for verbal lashing, and a vulnerable, unsure wife in need of gentle nurturing.

Kelsey handles the turns deftly and carries us along as we ride the rapids of her character's beliefs and feelings.

Williams brings a quizzical and ultimately sympathetic mien to Ian, a small, supporting role. Juliana and Ian interact only a few times, and their chemistry is marked at first by awkwardness. Williams and Kelsey do that dance together well.

"The Other Place" calls to mind the ancient allegory of Plato's cave. Sometimes, it seems, what we perceive as reality are just figments and shadows dancing on a wall.