Branden Jacobs-Jenkins’ talky new play The Comeuppance, which opened Monday at the Signature Theatre, is like a millennial version of The Big Chill, depicting a 20-year high school reunion from hell. In this case, almost literally, since the five characters we meet also occasionally step out of character to address the audience as the Grim Reaper (though Death seems to prefer more ancient names like Anubis or Magwayen or Yama). The actor’s voice is distorted (credit Palmer Hefferan’s sound design) as this dark angel wittily describes his symbiotic relationship with the living, and teases the reason why he’s hovering about this particular gathering.

The character most deserving of the promised reckoning of the title emerges early on: Emilio (Caleb Eberhardt) is a gangly artist with bleached-blond hair and enough chips on his shoulder to sop up several bowls of salsa and guacamole. This is a bit of a mystery since he’s arguably the most successful of his peers. He’s an installation artist with a big exhibition that’s about to open in New York and a 5-month-old daughter back at home in Berlin.

But it quickly emerges that he still carries resentment over his unrequited crush on his high school bestie, Caitlin (Susannah Flood), who’s remained in their suburban Washington, D.C., hometown and married a much-older ex-cop with two kids from a previous marriage (her hubby also has MAGA leanings that drew him to the vicinity of the Capitol riot — though he didn’t actually storm it, she’s quick to point out).

And Emilio is soon lashing out at just about everyone from his old hang gang, dubbed the Multi-Ethnic Reject Group (though issues of race and ethnicity are curiously absent from all of the classmates’ discussions). He snaps at Ursula (Brittany Bradford), who’s sporting an eyepatch as she is losing her sight, about lighting up a joint. He needles Kristina (Shannon Tyo), a military physician with five kids, about her heavy drinking. And he’s positively savage to Francisco (Bobby Moreno), Caitlin’s bully of a high school boyfriend still suffering mental health issues after five tours in Iraq and Afghanistan. Of course, he’s positively brutal to Caitlin herself, betraying multiple confidences in a misguided attempt to reclaim her attention.

Branden-Jacobs has a gift for naturalistic dialogue that is genuinely witty without seeming overly written, and the exchanges that occur on Ursula’s elegantly simple, dimly lit porch provide the sense that we are eavesdropping on a group of friends that have lost most of the things that had once drawn them together, and the awkward ways in which those gaps can surface. (It becomes clear, for instance, that most of them had assumed that Emilio was gay — a revelation that seems to fuel his retaliatory outbursts.) The cast, under the direction of Eric Ting, achieves the kind of onstage rapport you’d expect of people who’ve known each other a long time, if not always completely. Ting also manages the supernatural elements of the production (with Arnulfo Maldonado’s set design, Amith Chandrashaker’s lighting and Skylar Fox’s magic design) with aplomb.

But the show, at least in this world premiere version, is much too long — nearly two and a half hours, without an intermission — and the payoff promised in the title is too deflating to have much impact. (That sad-trombone final scene also follows a couple false endings, and missed opportunities for other conclusions, that enhance the sense of disappointment.) We’ve come to expect bigger climaxes from Jacobs-Jenkins, who’s shown us that he can bring down the house — in the case of his 2014 play An Octoroon, quite literally.