“How old are you when it’s too late to start being happy?” asks the 20-something Lili (Kate Arrington) plaintively.

The maid Olivia (Sharon Hope) answers “35” but the real answer seems to be “whatever age you are” for this bunch of droopy, bored and/or crazy characters in the Catskills, some on holiday.

Lili is there with her autocratic German-accented mother Eva (Sandra Shipley), she of the “looming late Ibsenesque figure,” gobs of money and a mean streak the size of Texas. They live in the imposing family home across the lake from the Borscht Belt hotels.

Lili has walked out on the pier when a waterlogged Adonis named Nick (Patrick Zeller), unaware this is private property, pulls himself out of the water. Conversation ensues (“I like the way you look,” says Lili, “like nothing ever happened to you.”) and romance will inevitably follow, though we will soon find out that very little is as it appears in this universe.

Richard Greenberg’s The American Plan plays through March 30 at the Old Globe’s Cassius Carter Centre Stage, directed by UCSD’s Kim Rubinstein.

Set in 1960, on the brink of major social changes, Greenberg’s characters are stuck in their self-imposed boxes, perhaps desiring change, but more inclined to pretend than to do the work required to effect the transformation.

When Eva meets Nick, she leads him to believe he may be the one for Lili, and soon after is asking, “Where shall we have the wedding?”

Predictably, this shall not come to pass. Mom does her research on the intended groom, finds him a dedicated liar (and, in fact, apparently bisexual), and that is that. The play ends in a coda in which it is clear that no one is happy.

This is Greenberg’s third Old Globe appearance (his Take Me Out won a 2003 Tony; last season’s The Violet Hour is the other) and in every one of his plays (as well as a fourth I saw in New York called The House in Town), I left wondering why I should care about these characters. Greenberg never gives me a reason. He seldom even gives me enough information to understand the characters. Why is Eva a dragon? Why is Lili crazy? Why is Nick a liar, and why would he even consider giving up his society girlfriend for this droopy (and loopy) girl? And what’s with his gay friend Gil (Michael Kirby), who seems to be a stalker?

The actors work their hearts out, but I never got the answers, and after a while, as with all Greenberg plays, I stopped caring.

The American Plan plays through March 30 at the Old Globe’s Cassius Carter Centre Stage. Plays Sunday, Tuesday and Wednesday at 7 p.m.; Thursday through Saturday at 8 p.m.; matinees Saturday and Sunday at 2 p.m. For tickets call 619-23-GLOBE or visit www.theoldglobe.org.

Love, laughter, betrayal, sibling relationships and, most importantly, housecleaning are the subjects of Sarah Ruhl’s The Clean House, the quirkiest, wackiest, most charming play of the season, playing through March 22 at San Diego Repertory Theatre. Sam Woodhouse directs.

Lane (Rosina Reynolds), a surgeon married to another surgeon named Charles (Ron Choularton), is clinically obsessive about neatness at home (a clinically all-white mecca down to the life-size statue of a whippet in the corner).

She complains at the top of the show about her Brazilian maid Matilde (Claudia Vásquez), who is too depressed to clean the house: “I took her to the hospital and had her medicated and she still won’t clean,” she wails. “I didn’t go to med school to clean my own house!”

Matilde (pronounced mah-CHILL-gee), you see, is busy trying to make up the perfect joke. For practice, she tells us an extended (and untranslated) joke in Portuguese, adding that her parents were the funniest people in Brazil and that, in fact, her mother died laughing at a joke her dad told. She even suggests that jokes have social importance: “If more women knew more jokes, there would be more justice in the world.”

But cleaning house? That’s not high on Matilde’s list of important things.

Fortunately for Matilde, Lane’s wigged-out sister Virginia (Annie Hinton) loves to clean and even walks around with a toilet brush in her purse. “People who give up the privilege of cleaning their own house are insane,” she says. “How do they know if they’ve made any progress?” Matilde and Virginia make a quiet deal to make sure Lane’s house is cleaned.

When Charles leaves Lane for an older Argentinian patient named Ana (Ivonne Coll) on whom he has just performed a mastectomy, Lane’s well-ordered but passionless life (“Even my cuts are superficial,” she notes) spins utterly out of control. Plot twists give her a chance to grow and perhaps change her perspective a bit.

Ruhl’s imagination runs to the goofy, and so does her storytelling technique, but her characters are such fun it’s easy to go along for the ride. There are screens to the sides of the stage where stage directions are projected: “Virginia takes stock of her sister’s dust;” “Charles performs surgery on the woman he loves.” Flashbacks take us to Brazil with Matilde’s parents. Ana’s house has a balcony which projects over and into Lane’s living room.

The Clean House requires actors who can do and say utterly bizarre things and make them look perfectly normal. Woodhouse is blessed with a powerhouse cast here. Reynolds is perfect (as always) and perfectly starchy; Choularton is strange and funny and rather touching as Charles; Vázquez is irresistible as Matilde and Coll is terrific as Ana. But my favorite is Hinton’s loopy Virginia, over the edge but so charming you can’t help but love her.

Kudos to Victoria Petrovich for her terrific, pristine set, and to Woodhouse for directing with a steady hand.

Playwright Ruhl is the recipient of a 2006 MacArthur Fellowship, a.k.a. “genius grant.” I can hardly wait to see what she comes up with next.

The Clean House plays through March 22 at San Diego Repertory Theatre. Shows Wednesday and Sunday at 7 p.m.; Thursday through Saturday at 8 p.m.; matinee Sunday at 2 p.m. For tickets call 619-544-1000 or visit www.sandiegorep.com.

Genetics, genius, and the inheritability of insanity are under consideration in David Auburn’s Proof, closing this weekend at Westminster Theatre in Point Loma. The Vanguard production is directed by David R. Pearson.

Catherine (Erica Soares), the 27-year-old daughter of mad University of Chicago math genius Robert (Michael Thomas Tower), left school to take care of her father in his last years. Blessed with some of his genius in the field, she is now nearly paralyzed by the possibility of following in his unstable footsteps. She lives in his house with her memories and his ghost. In flashback, he tells Catherine that he started to go downhill in his mid-20s.

She is pulled out of near hermithood by young Ph.D. Hal (Robert Hoadley), her father’s former student, who wants access to her dad’s 103 notebooks mostly full of mad ramblings. Hal hopes to find one last brilliant mathematical discovery in the lot.

Catherine is also awaiting the arrival of her sister Claire (Bebe Black), coming from New York for their father’s funeral. Claire, too, fears for her sister’s sanity and wants to take her back to New York.

Hal is ecstatic to find one last proof in a locked drawer upstairs, thinking it a last bit of brilliance from the genius. But when Catherine says she wrote it, the scene is set for a fascinating consideration of heritability, gender bias and trust. Who will believe her? Is she telling the truth? Could she have written it?

Auburn won both the Tony and the Pulitzer Prize in 2001 for this riveting play, and Vanguard does a fine job with it. Soares looks less disheveled than some Catherines I have seen, but seems every bit as tortured. Black’s Claire, a yuppiefied bean counter, is oblivious to her sister’s personality (she offers jojoba hair conditioner) but is genuinely interested in her well being. Hoadley hits the right note as the researcher who tries to bring some semblance of normalcy – and even romance – to Catherine’s life.

Exploring questions of conjecture and proof, trust and certainty, Proof is an interior piece full of emotional truth and betrayal.

Vanguard’s production of Proof closes March 16 at Westminster Theatre in Point Loma. Shows Friday and Saturday at 8 p.m. and Sunday at 7 p.m. For tickets call 619-224-6263 or visit www.westminstersd.org.