Don’t Get on This Mom’s Wrong Side : ‘The Walkers’ focuses on a Jekyll-and-Hyde housewife whose whole life is centered on her family.

Grace Walker couldn’t be nicer by day. But just don’t catch her when she’s sleepwalking.

“There’s the sunny side everyone sees--and then there’s the other side no one sees,” said Patricia Herd, who’s playing Grace, a Jekyll-and-Hyde suburban mom, in the world premiere of Barbara Lindsay’s dark family comedy “The Walkers,” which begins previews Wednesday at the Road Theatre.

“I can’t say too much,” the actress added tentatively. “I don’t want to give it away. Let’s just say she’s quite a bit different when she’s asleep--when this dark, black side comes out.”

Although Herd emphasizes that she hasn’t dipped into her own child-rearing memories for the part, the character isn’t totally unfamiliar to her. “I do know a lot of people like Grace,” the actress said. “She wants to make the best of everything, wants everyone to be happy. She’s pretty much house-bound, never had a job. Her whole life is centered around her family. It reminds me of the ‘50s; I grew up like that, so I can certainly relate. And when you act, you always use a part of yourself.”

If anyone knows how much of Patricia is going into Grace--and vice versa--it’s the actress’s co-star Richard Herd, her real-life spouse of 13 1/2 years.

“It’s the first time we’ve worked together (on stage),” Richard said. He’s playing patriarch Boyd Walker in the six-character play, which, he said, features “a dysfunctional family, like I guess a lot of American families are, but don’t want to admit.”

He added: “In real life, we have a very functional family.” That includes a blended union of grown offspring: Patricia’s daughter and Richard’s daughter and son.

Born in Boston, Richard worked his way through regional stock to New York, where he acted in “live television, live soaps--anything I could get.” His big break came with the role of James McCord in “All the President’s Men,” followed by “F.I.S.T.” and “The China Syndrome”--which led to his move to Los Angeles.

University of Houston graduate Patricia appeared at the Margo Jones Theatre and Alley Theatre in her native Texas, but, after resettling locally in 1959, was absent from acting for many years, teaching elementary school, selling real estate and working with theater-improv guru Viola Spolin.

Introduced 15 years ago at a New Year’s Eve party, the Herds have been spending a lot more time together of late. In addition to doing “The Walkers,” Patricia recently filmed an episode of Richard’s NBC series “SeaQuest,” playing wife to her husband’s character, Adm. William Noyce.

It’s not the first time that Richard has held down two shows at once: During the ‘80s, he shuttled between the TV series “T. J. Hooker” and “V”--and next month, he’ll switch into multiple gears again when he begins shooting the mid-season replacement “Winnetka Road,” a new nighttime soap from Aaron Spelling.

So why take on a small theater project?

“I’d worked with (director) Dan Butler twice before,” said Richard, whose local stage credits include “Other People’s Money” at the Westwood Playhouse. “This is a well-written play, and it has things that I think will touch everyone. Also, it’s an opportunity to work with my wife.

“I’ve never done an Equity waiver before. But sometimes you have to reach out and help a deserving group of burgeoning souls, and this is a good production, a good company. It’s also a workout, like going to a gymnasium--and it’s a commitment. You do waiver for yourself, because you want to do the work.”

Where and When What: “The Walkers.” Location: The Road Theatre, 14141 Covello St., No. 9-D, Van Nuys. Hours: Opens Nov. 5 and plays at 8 p.m. Thursdays through Sundays. Closes Dec. 12. Price: $12.50. Call: (818) 785-6175.