THEATER REVIEW:

Did she or didn’t she? And if she did, with whom? That’s the haunting, unanswered question that hangs over the stage at the final fadeout of “Our Mother’s Brief Affair,” the latest world premiere from Richard Greenberg at South Coast Repertory.

This 90-minute examination into semi-familiar Greenberg territory (its characters are derived from another Greenberg South Coast Repertory premiere, “Everett Beekin,” in 2000) introduces two certified “spoilers” — plot twists that should not be revealed here, in deference to future audiences. It also thrusts the spotlight on one of the finest individual performances on the Costa Mesa stage this season.

That would be Jenny O’Hara’s title character, Anna, who’s on her latest deathbed and whose condition brings daughter Abby (Marin Hinkle) to New York from California (Laguna Beach, in fact), joining her twin brother Seth (Arye Gross), a local obituary writer.

O’Hara fluctuates between the ditzy elderly woman from the present era and the somewhat naive mother of teenagers she was in 1973 when the incident in question occurred. Her interpretation of this possibly deranged character is superbly rendered.

The fact that both twins are homosexual (Abby has a lover and two children back home; Seth is a loser on the relationship battlefield) is sort of tossed in for good measure, never really defining their characters. Their alternate probing sessions with Mama produce the real grist for this dramatic mill.

Enacting Anna’s lover (and, briefly, her soulless husband), Matthew Arkin brings a new element into the equation, particularly when he discloses his true identity — one which might be a deal breaker under most circumstances. This opens a new can of worms, on which the lovers endeavor to keep a tight lid.

Had they been produced 50 years ago, Seth and Abby might be J.D. Salinger’s Franny and Zooey, two Jewish siblings grown into an uncertain adulthood.

Gross forces his case with prosecutorial vigor, while Hinkle contributes grimly bitter reactions.

Under the crisp, intelligent direction of Pam MacKinnon, “Our Mother’s Brief Affair” succeeds in making a largely talky play quite mesmerizing. Jenny O’Hara’s performance, which touches a variety of dramatic levels, is one that should not be missed.

Sybil Wickersheimer’s exterior setting — park benches which also function as beds or interior furniture — is as simplistic as it gets at South Coast Repertory, and also as effective.

IF YOU GO

WHAT: “Our Mother’s Brief Affair”

WHERE: South Coast Repertory, Segerstrom Stage, 655 Town Center Drive, Costa Mesa

WHEN: 7:30 or 8 p.m. Tuesdays through Fridays, 2:30 and 8 p.m. Saturdays, and at 2:30 and 7:30 p.m. Sundays until May 3

COST: $28 to $64

CALL: (714) 708-5555

TOM TITUS reviews local theater for the Daily Pilot. His reviews appear Thursdays.