The emerging playwright Abbie Spallen has several of the qualities often associated with her native Ireland: an ear for the music of ordinary talk, a keen sensitivity to beauty, a tragic bent tempered by a hearty sense of humor. All are on display in the Manhattan Theatre Club’s production of her drama “Pumpgirl,” which arrives in New York on the heels of successful runs in Edinburgh and London. But while this strange, strong brew confirms Ms. Spallen’s promise, she seems to have gotten its proportions wrong. There’s too much ominous plotting, and too little of her sparkling wit, to fully satisfy.

Still, “Pumpgirl” holds your attention, in part thanks to its deft use of theatrical contrasts. Though the play’s three characters are inexorably bound together, Ms. Spallen never allows them to interact. Instead, standing or sitting side by side on a clear glass platform, the three actors take turns delivering long, present-tense monologues, or lingering silently in the nearby shadows. Underneath the glass platform lies the soil of their rural hometown, covered in scrub and wildflowers (skillfully realized by the scenic designer, David Korins). But little else blooms in this landscape littered with the smoldering butts of burned-out love.

“In this town you’re either a slut or a snob, no in-betweens,” says Sinead (a wonderfully feisty Geraldine Hughes), the long-suffering wife of the vain, underemployed Hammy (Paul Sparks). Sinead is one of the snobs: She has two kids in tow, a no-good husband, and a biting wit fed by inexhaustible stores of disappointment. The pumpgirl (Hannah Cabell), a butch gas station attendant Hammy sometimes picks up for sex in the back of the car, is one of the sluts: disrespected by the lads, hated by their wives.

In the stronger first act, Ms. Spallen settles into her best mode: easygoing, affable storytelling. The stories aren’t about much — a trip to the market, a customer at the pump, a day at the local racetrack. But each of the three actors can tell a tale, and these tales feel like real people’s stories, peppered with local details and pop culture references.

As the first act draws to a close, though, the plotting machinery starts to churn. From here on out, the tension is artificially increased by a succession of episodes worthy of a pulpy Hollywood thriller. Before long, it feels as if Ms. Spallen is dutifully ticking off milestones on some screenwriting how-to chart. Once the plotting takes a turn for the melodramatic, the rapport between the characters and the audience wavers. The wide array of Irish accents that we were willing to forgive in the first act becomes distracting in the second. The ban on dialogue begins to seem stymieing. And Carolyn Cantor’s direction — so nimble in the opening sections — starts to feel heavy-handed.

Despite its flaws in the plotting department, “Pumpgirl” announces the arrival of a writer of considerable gifts. Though their actions may not always be believable, the characters nonetheless are — largely because Ms. Spallen’s meticulous ear picks up the unique habits of speech and thinking of each. They stand before us, three essentially likable people hungry for understanding and unable to connect with anyone — except, strangely, us.

By the end of “Pumpgirl,” we know these characters better than anyone — and far better than they know each other. The play’s surprising poignancy comes from the fact that such knowledge is wasted on us. We can’t do a thing about their lonely lives.

Until January 13 (55th Street between Sixth and Seventh avenues, 212-581-1212).