There are unreliable narrators, and then there are guys like the one who greets us in Bubba Weiler’s lovely and haunting new play, “Well, I’ll Let You Go.” Identified in the script simply as “a man in a gray suit,” this fellow proves such a dependable and vociferous font of information that he makes the Stage Manager in “Our Town” look like a slacker.

The man in gray is, in fact, so thorough in his description of the other characters who figure into this one-act piece, so detailed in relaying their back stories and inner lives, that at first he may seem like an expositional crutch. You may wonder, briefly, why Mr. Weiler couldn’t figure out a more graceful way to share some of this information.

Soon enough, though, it becomes painfully clear why this narrator — brought to life in a beautifully measured performance by Michael Chernus, a stage veteran more widely known for his work on screen in series such as “Severance” and “Orange is the New Black” — feels so compelled to tell us so much about these people, and why he observes them so keenly, either onstage or from a seat left free among the audience, when he isn’t speaking.  

Saying much more would require spoiling a revelation that is delivered gradually in this staging, directed with great nuance by Jack Serio, a rising talent whose previous credits include an exquisite “Uncle Vanya” produced in a private Manhattan loft two summers ago. “Let You Go,” which features sharper twists as it progresses, feels almost as intimate, even in the substantially larger setting offered by Brooklyn’s The Space at Irondale.

Mr. Weiler, who is still in his early 30s and better known as an actor than a playwright (credits include Broadway’s “Harry Potter and the Cursed Child”), has set his play in the kind of small town Thornton Wilder might have studied had he been born a century later. “Once home to the most fertile farmland in the country,” as the narrator informs us, “it was slowly and steadily paved over to become an unremarkable but nice American suburb.”

Indeed, social changes just as profound as those under way in “Vanya” have plainly informed the lives of the men and women we meet in “Let You Go.” But they serve as an undercurrent, with the emphasis squarely on the personal drama enfolding Mr. Weiler’s characters. A former teacher named Maggie, long married to a lawyer named Marv, is the central figure; the play unfolds as her life has been upended by a sudden and grotesque tragedy.

As Maggie, played by a predictably fine Quincy Tyler Bernstine, is visited by a succession of well-meaning people, from relatives to strangers, Frank J. Oliva’s initially spare set becomes cluttered with tokens of sympathy and gratitude: flowers, balloons, even a pile of mulch. As the gifts accumulate, Ms. Bernstine wrenchingly conveys both Maggie’s grief and her resilience, seeming small and defeated in early scenes but acquiring grit and warmth.

The cast includes other redoubtable troupers such as Constance Shulman, characteristically tart as an overzealous church representative, and Danny McCarthy, who strikes the perfect balance between amiability and vague menace as Maggie’s elusive brother-in-law. Cricket Brown, a younger performer, brings gentle humor and gorgeous pathos to the role of a college student who meets with Maggie in the play’s moving final scene.

By that point, “Well, I’ll Let You Go” has emerged as a celebration of love and decency, and a testament to their transcendent powers — even in the darkest of times.