The main attraction of Deborah Grimberg’s new Cycling Past the Matterhorn is Shirley Knight, whose still-radiant presence elevates even this extended doodle of mother-daughter angst. Cards on the table: It’s a small performance, not one for the record books. Still, it’s a lesson in discreet artistry and consummate professionalism. Knight plays Esther, a middle-aged English woman whose husband left her after 30-odd years of marriage. Her daughter, Amy (Carrie Preston), a psychic trying to make a professional go of it, would like to abandon her too, now that she’s discovered her mother will soon be blind. Habitually flying into hysterical tailspins, Esther takes up a lot of domestic space. Knight, who never reveals more than what’s needed, though always more than you’d expect, lets you feel the seismic shocks threatening yet another emotional earthquake. More impressive is the way she reveals the grit of a woman determined to live a little more despite how washed-up she feels—even if it means buying a bike, wrestling her full figure into shape, and cycling across the Alps. Under the direction of Eleanor Holdridge, Knight and Preston find whatever truth there is in Grimberg’s drama, and Brenda Wehle, as Esther’s tacky, straight-shooting sister, maximizes the outré humor.