Well, Michael Cerveris certainly has a type. Fresh off of last spring’s misguided revival of Hedda Gabler starring Mary-Louise Parker, Cerveris is co-starring with another actress giving an anachronistic performance in a period piece: Laura Benanti in Sarah Ruhl’s In the Next Room(or the vibrator play). But Benanti is no Mary-Louise Parker.

Ruhl (The Clean House, Eurydice) has conscientiously eschewed (mostly) her trademark magic realism for something far earthier in her new play, about Dr. Givings (Cerveris) who, in the early days of electricity, blithely treats “hysterical” women with the titular device while his wife (Benanti) waits in the next room. But, like a dim Victorian drawing room filled with antimacassars, bulky furniture and knick-knacks, she’s also crammed her play with an excess of plot. The premise is based on historical facts, but Ruhl has managed to take a fascinating topic and present it in the most obvious way possible, with homoeroticism, free-love advocating artists, Greek scholars and plenty of race and feminist subtext.

Front and center is Benanti, as the world’s least likely Victorian. She chatters away blithely, about dead children to a recently bereaved mother or in a racist vein in front of the African-American help, then immediately apologizes for it as if she lives in today’s politically correct world. Everyone else on stage at least tries for an approximation of 19th-century attitudes; Benanti and director Les Waters attempt to pass off her incongruousness as a deliberate choice, pointing up the rigid lives Victorians led. But she’s so relentlessly modern that the play eventually begins to feel like a flimsy pretext for a heavy-handed sermon, as if a secret message was hidden beneath the women’s voluminous skirts.

When the secret message actually turns out to be that men don’t understand female sexuality, and women chafe under patriarchy, it’s both a shock and a disappointment. What has made Ruhl such a fresh voice has been her ability to transform the prosaic and ordinary into a something breathtaking; the rain of stationery at the end of act one in Dead Man’s Cell Phone remains one of the most moving theatrical moments I’ve seen. But a correlative moment at the show’s end (featuring a full frontal nude scene from Cerveris) feels tacked-on, as if Ruhl worried that the lack of such a moment would render the play unrecognizably hers. And though she wrings some comedy out of Dr. Givings’ patients and their confusion about the affect his treatments have on them, she never ventures far enough with it. No one really seems to change after they finally unlock their orgasms; Maria Dizzia’s patient giggles a great deal more and Benanti just becomes a little more grating until she eventually overpowers her husband.

The rest of the cast (Wendy Rich Stetson, Thomas Jay Ryan, Quincy Tyler Bernstine and Chandler Williams) are left with clichés to play: the regal African-American wet nurse, the repressed lesbian, the coarse husband, the absurd European artist. Ruhl seems to have spent so much time on research that she forgot to write memorable characters.

>In the Next Room (or the vibrator play)

Open run, Lyceum Theatre, 149 W. 45th St. (betw. 6th & 7th Aves.), 212-239-6200; times vary, $46.50–$96.50.