Airing clan’s secrets, politics with wit, wisdom

Herzog, who developed the play last year on a fellowship at Williamstown, has said that it draws on her own background as part of an extended family of politically active Marxists. That family history shines through in the affectionate, complicated, and often quite funny way her characters talk with one another. Steeped in the history of the American Communist Party, they’re also moving, sometimes awkwardly, into a complicated new age — not quite our own, but the Clinton-era year of 1994, when revelations that some blacklisted Communists really had been Soviet spies created uncomfortable fissures in families like Herzog’s fictional Joseph clan.

What’s remarkable in so young a writer is how fully she creates characters of three generations: Vera, the widow of the family patriarch, Joe Joseph, who staunchly defends his Stalinist loyalties; Emma, the passionate young law-school graduate, who has founded a fund named for Grandpa Joe but later wonders if her faith in him is misplaced; and Ben, Emma’s father, a weary Marxist high-school history teacher who mediates between the two. Add Ben’s less politically engaged brother, his passionate but pragmatic second wife, Emma’s conflicted boyfriend, and her troubled sister, and you’ve got a rich network of relationships that many a more seasoned playwright would have trouble sorting out.

But Herzog does it with grace and depth, in a series of verbally dense but lively scenes that gradually unspool the family’s secrets, affections, and mutual disappointments. McCarthy-era compromises and principled stands, ’80s materialism, and identity politics all play a part in the story, yet all are unpacked with surprising clarity and precision. The only reference that might have benefited from more exposition would be the trial of Mumia Abu-Jamal, the Philadelphia activist/journalist whose controversial 1982 murder conviction has left him on death row ever since. (The program notes do offer a helpful summary.)

The relevance of that case, however, quickly becomes evident as the family fights over Grandpa Joe’s legacy. Granddaughter Emma’s fund is largely devoted to freeing Mumia, arguing that his guilt or innocence is less important than his alleged railroading at the hands of police and prosecutors. The dispute over Joe’s actions in the ’50s is framed in similar terms.

But all of this might seem dry if it weren’t for the wit and crackle of Herzog’s dialogue, and the ways it illuminates the complicated, shifting, and very believable relationships among all the people onstage. “Political’’ plays often draw a sharp distinction between large public actions and smaller private lives, presenting politics as an abstraction engaged in by stick figures. The beauty of “After the Revolution’’ is that it shows us profoundly political people who are also profoundly human. The texture and grit of family life, even and perhaps especially of life in a highly political family, come through in every scene.

No doubt it helps to have one of the strongest casts I’ve seen in a while. As Vera, Lois Smith starts out so persuasively scatterbrained that I almost feared it was the performer, not the character, who was forgetting words, but no worries: This is a brilliant performance, a multifaceted portrait of a woman who’s idealistic and practical in equal measure, and who’s terrified both by her own forgetfulness and by the fear that her generation’s legacy will be forgotten by those who come after. Katharine Powell’s Emma provides a fiery counterpoint, no less committed and no less hampered by her own weaknesses.

As Ben, Peter Friedman is just heartbreakingly good. We see his devotion to his daughter and his fear of causing her pain, which inadvertently leads him to cause more pain by keeping secrets from her; we also see his deep political commitment and his weary recognition that it’s not, in fact, going to change the world. His conversations with Emma, whether affectionate or infuriated, are among the play’s most deeply felt and deeply believable.

In smaller parts, Meredith Holzman gives warmth and self-aware humor to what could have been the shallower role of Emma’s sister, freshly out of rehab and sadly amused by the father-daughter conflict that, for once, doesn’t feature her own failures. Mare Winningham doesn’t have much of the “Midwestern’’ accent that Ben’s wife is meant to, but she’s otherwise a strong and vivid presence. Mark Blum as Ben’s less political brother, Elliot Villar as Emma’s boyfriend, and David Margulies as an old ally of Joe all contribute perceptive and multilayered portraits of fascinating characters.

“After the Revolution’’ is full of talk, full of feeling, full of life. It may seem too full to those who aren’t naturally drawn to its subject. But for anyone who’s ever battled to find a place in a complicated and sometimes maddening clan, this is a play — and a family — to remember.

Louise Kennedy can be reached at kennedy@globe.com.