This is the season when the potato fields and duck ponds of Long Island's swanky Hamptons suddenly come alive with the sounds of city people, cocktail shakers—and summer theater. The only problem is that this month's local production of three one-act plays might blanch the suntans from the faces of some patrician audiences. In one segment, Dina Merrill, that most impeccably elegant of actresses, raucously plays a disheveled, adulterous housewife whose coitus becomes interruptus with her lover's sudden death. Then in a jiffy she's back again as a rigidly Teutonic child psychologist with a boot fetish. "My husband wanted a different image for me," explain Merrill with a fond look at her actor mate, Cliff Robertson. "He thought I might be a little typecast."

The production marks a rare public pairing of one of America's most prominent showbiz couples. Robertson, 55, wrote and directed the psychologist role for Dina, also 55, who performed at scale ($500 a week) to benefit the 50th anniversary of the area's John Drew Theater. Another local acting couple, Anne Jackson and Eli Wallach, joined in—as did playwrights Murray Schisgal and James (A Chorus Line) Kirkwood, who wrote Dina's lethal love tryst. "The theater asked us to do this, and I did out of guilt for the community," explains Robertson.

Robertson and Merrill live nearby in the East Hampton home that's been their summer quarters most of the 14 years of their marriage. They met in 1956 at Gary Cooper's place in Hollywood. Dina, the wealthy daughter of Wall Street financier E.F. Hutton and cereal heiress Marjorie Merriweather Post (Merrill is a stage name), had gone west for a screen test. Cliff, the son of a wealthy Southwestern land baron, was fresh from the New York stage. "I thought she was beautiful and sweet," he recalls. "She wasn't like the Hollywood tootsies."

At the time, however, Dina was married to businessman Stanley Rum-bough Jr., a Colgate heir. "Stan wanted me to be a housewife and mother," she says. "But after eight years I had gotten antsy. Men think we can't do two things at once. They can't, but we can. Women are more resilient." Merrill and Rumbough were divorced in 1966, and Dina and Cliff married shortly thereafter. (Cliff's first wife was Cynthia Lemmon, Jack's ex.)

Dina has since appeared on Broadway (Angel Street) and in films (Just Tell Me What You Want), while Cliff made movies like J. W. Coop and 1976's Obsession (broadcast on ABC last week). Ironically, though, the Hollywood role he is perhaps best known for came in 1977 when he courageously (some say self-destructively) accused David Begelman, then chief of Columbia Pictures, of forging a check. Since then, Cliff has not worked for a Hollywood studio. "But I can't spend the rest of my life gnashing my teeth," he shrugs. "I have no animus toward Mr. Begelman [who was convicted, put on probation and is now head of MGM]. There are people who are more to be pitied than censured." Dina is more outspoken: "I've been worried about the effect not working has had on Cliff," she says. "He's pretty controlled, but I know it's taking its toll."

Neither of them needs Hollywood, considering Dina's wealth, but Cliff is quick to insist that "I never wanted to be a consort. Dina goes her financial way and I go mine." He wouldn't, for example, dream of asking her for funds to finance a sequel to Charly, his 1968 Oscar winner. "I'm old-fashioned about that," he reports. "I couldn't afford it," retorts Merrill, who bristles at the "socialite-actress" label sometimes given her.

But the Merrill-Robertson merger, as E.F. Hutton might have said, has provided some valuable assets, ranging from their daughter, Heather, 12, to a combined social conscience. Dina is especially devoted to the Juvenile Diabetes Foundation. Her son David, one of three children by Rumbough, was stricken with the disease at age 14. (He died in a boating accident nine years later.) "I can feel him looking down on me smiling: 'Go, Mom, go!' " Says Merrill of her work for the foundation. At other moments Dina revels in her new position as the first female member of the board of E.F. Hutton. Is she a token? "Yeah, sure, but so what," she says. "It's a sentimental journey back to my roots."

The trip forward is less well plotted. Merrill is contemplating everything from Shakespeare and Ibsen to musical comedy, notably The King and I. Cliff intends to write and direct more, since, as Dina notes, "I don't think it's going to change for him soon in Hollywood." Both of them hope to see their theatrical collaboration go further, and indeed a few producers were nosing around at the opening last month. Certainly the Robertsons didn't do it for the money. "They could be stealing me blind," jokes the Hollywood whistle blower, "and I wouldn't know the difference."