Of all the plays in Gina Gionfriddo’s acerbic, insightful oeuvre, 2012’s Rapture, Blister, Burn is the one that faults along the most predictable lines. It compares and contrasts a pair of former roommates, now in their early 40s. Catherine is an academic successful enough to be an occasional panelist on Real Time with Bill Maher; single and childless, she writes about feminism through the prism of porn and horror movies. Gwen is a stay-at-home mom to a 13-year-old and a 3-year-old, muddling through her stultifying marriage to Don, the dean of an undistinguished liberal arts college somewhere in New England. What’s that thing the grass always is?

Catherine’s semi-voluntary re-entry into Gwen and Don’s lives comes when she moves back home to help care for her ailing 70-something mother. The fact that Catherine’s mom happens to live in the same college town where Don has found a comfortable position that suits his low-exertion temperament is the least of the contrivances that make Gionfriddo’s very funny play sound like a terminally unfunny movie. But the execution is all. Gionfriddo—and the sturdy-to-sterling cast director Shirley Serotsky has pulled together—makes us care about these vividly imagined characters, each of whom has compromised herself in her own way.

As Catherine, Michelle Six—who played the title role in Round House’s production of Gionfriddo’s Becky Shaw in 2013—comes off as stiff and distant in the lengthy opening scene, but she finds her groove once the action moves to her mom’s living room, where Catherine teaches a summer seminar through Don’s college for two students, complete with cocktails. Plausible? Who cares? It’s enough that she gets to debate 21-year-old babysitter/former stripper/aspiring reality TV star Avery’s shrugging embrace of promiscuity and nonchalance about porn. Catherine even invites her mother—the convalescent, played by Helen Hedman—in to recall the distant years when going stag wasn’t an option.

Eavesdropping on four women of three generations debating the merits of Phyllis Schlafly’s ardent anti-feminism doesn’t sound like a barrel of laughs, maybe, but these are the strongest scenes, thanks largely to Maggie Erwin. In the role of Avery, she comes perilously close to walking away with the show in her back pocket, using her blunt, skeptical delivery to wring laughs from lines that don’t announce themselves on the page as jokes. Erwin pulled off the same trick in Studio Theatre’s megahit comedy Bad Jews, which she left three weeks ago to join Rapture. (She couldn’t have known Jews would play for 15 weeks, the longest run in Studio’s 36-year history.) That the pragmatic Avery contrasts so sharply with the beatific, slightly dim WASP she played at Studio is a compliment to Erwin’s versatility.

Tim Getman conveys Don’s slacker charm without breaking a sweat; he’s consistently strong and familiar enough that we probably undervalue him.

Of the production elements, only Matthew M. Nielson’s musical score rings false. It’s barely there save for when it blasts over the scene changes, but those ersatz U2 riffs don’t suit the caustic story being told.

To those familiar with The Heidi Chronicles—Wendy Wasserstein’s Tony- and Pulitzer-winner of a generation ago, about a single academic who hits her 40s and feels betrayed by the feminist movement she’d long championed—Rapture can’t help but feel like a sort of intentional update. Gionfriddo protested in a New York Times essay when the play premiered in 2012 that she didn’t intend her play as a response to Wasserstein’s, “but no one is ever going to believe that.” She’s wrong. I’ll believe anything Gionfriddo tells me. Even if, or perhaps because, it resists synopsis.

4545 East-West Highway, Bethesda. $30. (240) 644-1100. roundhousetheatre.org