Deborah Grimberg’s “Cycling Past the Matterhorn,” a working-class London variation on the popular sisterhood drama, is set in a familiar world of strong, exceptional women and weak, mediocre men who are pretty much irrelevant. What counts in this world is female friendship, which has the power to make up for a whole host of ills: bad health, bad men, bad kids, bad jobs, and just plain loneliness.

Fantasies of female friendship live or die by their leading actresses, and “Matterhorn” is lucky in its trio of leading ladies. Tony winner Shirley Wright plays the ailing, middle-aged Esther, recently deserted by her cheating husband. Obie winner Brenda Wehle plays Esther’s loyal sister Anita, whose husband left a while back. And the capable Carrie Preston shoulders the large role of Esther’s 24-year-old daughter Amy, who is liking her first taste of grown-up independence and isn’t at all sure she wants to stay at home with Mum.

And there’s the rub – Amy doesn’t really fit into the sisterhood of the traveling tea cozies. She’s a rather liberated girl in her clashing rainbow outfits, reading palms at a market stall. It is Amy who causes the play to lurch off-center, and it is her character that shows just how conflicted the playwright is about female solidarity.

Amy enters with a wave and addresses the audience directly, working the room as a kind of narrator/stand-up comedienne. She has finally gotten out from under her parents’ influence and taken her own flat. Just when her own life is getting started, her father has dumped her mother – and now her mother is going blind. She tells the audience point-blank that she has no intention of living out her life as Esther’s caregiver. Young people, she asserts, are supposed to have their own chance at life, and she’s going to take her chance, no matter what. If she has to, she’ll leave London.

Amy’s aunt, the very tough cookie Anita, forces her to make good on that vow. Anita, the standard-bearer of family obligation, sits with Esther in the evenings, and has no patience with anyone putting personal desires before family. To Anita, the worst thing a woman can be is “selfish.” Though Anita plans to stand by Esther to the end, she still wants Amy to move home. When Amy refuses, she wages an all-out campaign – to no avail. Amy can’t accept the compensations of the female circle – not yet. She’s still young and optimistic. She still wants a career and a man. So she gets engaged to a pleasant-enough American bloke (yet another mediocre man) and packs her bags.

“Go on, sod off to America!” the pitiable Esther shouts bitterly at her daughter. “Stock up my freezer with TV dinners and call me on my birthday!” And this registers as an accurate image of what will likely happen if Amy goes. Yet it’s the playwright’s achievement to have made us feel that Amy’s own unformed life deserves its chance.

But having made this leap across to Amy’s side, the play backs down. Amy’s path is clear, but Ms. Grimberg can’t carry it through. So in the second act, the machinery comes down and – deus ex machina – the dim fiance abruptly changes his mind about Amy. Aunt Anita is magically removed, leaving the blind Esther alone and in extremis. Amy won’t volunteer, so she gets drafted.

Why doesn’t she resist? Where is her fight? Early in the play, it seemed that Ms. Grimberg’s flashes of brutally honest wit and insight would carry the day. It was a brilliant stroke to suggest that, after years of listening to Esther criticize her appearance, Amy vaguely welcomed her mother’s onrushing blindness – no more critiques of her striped shirts and shapeless sweaters! Amy’s revelation was cold and even heartless, but not more heartless than her mother’s endless digs about her looks.

On her return, the once-feisty Amy laments her selfishness and gallantly takes on the role of caregiver. We are back in the idealized sisterhood mode, and the final scenes are directed by Eleanor Holdridge to accentuate their cozy warmth, as if it had all come right in the end.

But had it? During Esther’s climactic bike ride past the Matterhorn, she was awed to realize “how incredible the world is, and how small my life had become.” Yet by the play’s end, Esther is pleased to have her daughter living at home, working in a grocery, with no man or career in sight. Who’s selfish here?

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