The three men — one young, one middle-aged, one old — waiting in the antiseptic bus terminal barely acknowledge each other’s existence. Yet each man’s story evocatively echoes the others’ in “Port Authority,” the slender but affecting play by Conor McPherson that closes the Atlantic Theater Company’s season.

Written in 2001, a few years before Mr. McPherson’s “Shining City” and “The Seafarer” (both recently produced on Broadway), “Port Authority” is steeped in loneliness. Even the format is isolating: The three Dubliners take turns addressing the audience, parceling out their stories in five-minute chunks of monologue. When they aren’t speaking, the director, Henry Wishcamper, has them recede into the background; they stare off into space, or turn their backs to the speaker. The effect is that of three separate portraits, hung side by side on a nondescript wall.

The wispy stories these loners tell are right in Mr. McPherson’s bailiwick — tales of crushed hopes, lifelong regrets, and women loved from afar. In a Dublin strictly stratified by class, random incidents usher men into worlds not their own, tempting them to reach for things they aren’t allowed to have. It’s a sorry universe, made livable by drink and a dry sense of humor.

Yet despite the overall gloom, each man hoards a secret, stubborn romanticism that can burst without warning into full, tender bloom. Young Kevin (John Gallagher Jr.) finally has to admit he’s in love with his pal Clare when he sees her shaking a little stone out of her shoe at the bus stop; he deals with this terrifying news by going to bed with a barmaid. Quailing at the prospect of a posh party at his new boss’s mansion, middle-aged Dermot (Brian d’Arcy James) tries to drown his working-class allegiance in gin and tonic, but it still bubbles up when he sees a woman who looks like his mother putting a dish of potatoes on the table. Joe (Jim Norton), a 70-year-old widower living out his days in a nursing home, gets a surprise package in the mail containing a photograph of a woman he once loved, and suddenly there’s a spring in his step.

Mr. McPherson has a remarkable facility for telescoping his characters’ dilemmas. At times they feel small and ordinary, just another day of life. Then, without warning, they swell to operatic dimensions, growing large enough to constrict a man’s heart.

If the unadorned monologues of “Port Authority” deprive one of some of the more interactive pleasures of theater, they do furnish some of the consolations of literature. Some lines have the clarity of poetry (“She had a silver bracelet on her left arm and she had a tan and I was watching it when she changed gears / And projecting ahead like we were married and this was what we did all the time”). And there are sequences with the dimensions of a novel — like the passage in which a raging all-night house party ends with Kevin and Clare abandoning their dates and embarking on a long, agonizing walk at dawn.

The power of Mr. Wishcamper’s no-frills production derives largely from its powerhouse performances. Fans of Mr. McPherson’s work will remember Mr. Norton from his turn in “The Seafarer,” and here again he shows an unerring instinct for handling the writing’s crosscurrents of humor and pathos. (He has a marvelous way of conveying a sprightly spirit in a ramshackle body.) The other two actors don’t share his mastery of the accent, but they feel the rhythms of the language. Mr. d’Arcy James accomplishes the tough assignment of subtly unveiling the layers of a proud, defensive man. And Mr. Gallagher’s performance captures the special vulnerability of a sensitive young man’s first, heart-pounding romance.

Mr. Wishcamper staged the monologues in the fluorescent-lit waiting room of a bus station (though the play’s setting is more metaphorical than literal). Other than some unnecessary and often inaudible sound design, there is little to distract from the storytelling, which is all to the good. And though there are a few moments when the direct-address format becomes a bit too in-your-face, attempting to converse explicitly with the audience, the characters mostly stay in their suspended orbits.

This is, after all, a meditation on male loneliness — on hearts that keep their own counsel, no matter the cost. The way the three stories illuminate one another has less to do with the handful of shared references that link them than with a growing sense of a particular brand of solitude that seeps through three generations. Like that solitude itself, “Port Authority” is a small-scale experience. But it is nonetheless an impassioned one.

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