IT IS "AN extraordinary turn of events," according to Robert Whitehead.

Zoe Caldwell calls it a demonstration of the theater's "evolutionary process . . . a sort of passing on." And Dame Judith Anderson says, "If anything ever came full circle, this is it."

They are talking about "Medea," which begins previews Wednesday at the Kennedy Center. Twenty-five hundred years have slipped by since Euripides wrote this blood-curdling saga of a barbarian woman's revenge on the ambitious husband who deserts her. The play has been revived a number of times down through the intervening millennia, so it is not the mere fact of another "Medea" that has its producer/director, star and principal supporting player using such high-blown metaphors. It is, rather, the strange sequence of chance encounters, bizarre parallels, hard words and shared memories that has brought this particular foursome--three people and a play--together again.

Judith Anderson, the eldest of the three, was born 84 years ago in Adelaide, Australia. After early exploits as a child prodigy in the singing, acting and "total showoff" departments, followed by a teen-age career on the Australian stage, Anderson emigrated to the United States, accompanied by her mother and a letter of introduction to Cecil B. De Mille. In San Francisco, "I got off that boat and ran up and down the wharf yelling 'I'm here! I'm here! Listen, I'm here!' " she says. But De Mille gave her a cool welcome. "I had no clothes, I had no looks, I was homely, and he didn't want any part of me."

So she came East to try the theater. At first the going was rough and "my little mum was sewing to get pennies for potatoes," says Anderson. Then she began to find work, joined a group called the 14th Street Repertory Company, and was even offered the lead in a Broadway show. But "the next day I got kicked out because I wasn't pretty enough," she says, adding, "Well, look at my face! I can't play some Pollyanna!"

Triumph came in the '30s, with the role of Gertrude in the John Gielgud "Hamlet," followed by Lady Macbeth in the Laurence Olivier "Macbeth." Then came the malevolent Mrs. Danvers in "Rebecca."

During the war, she met the poet Robinson Jeffers, after becoming infatuated with his "Tower Beyond Tragedy," an adaptation of Aeschylus' "Oresteia." Anderson failed to launch a production of the play, but later, whenthe legendary producer Jed Harris approached her about playing Medea, she suggested that Jeffers should translate that work, too. And Jeffers jumped at the idea, composing an unusually lean, stripped-for-action version of the play. But Harris' production plans languished, and it looked as if "Medea," like "Tower Beyond Tragedy," would become an item for bookstores rather than theaters.

Dissolve to 1946. A young actor/stage manager named Robert Whitehead has just returned to New York after several years of war duty in North Africa and Asia. Hungry for work, Whitehead was lucky enough to get cast in touring productions of "Burlesque" with Bert Lahr and "Night Must Fall" with Dame May Whitty. But beyond those engagements, he had doubts about his employment prospects, "and I didn't have the same feeling about hanging around coffee shops with unemployed actors as I had before the war," he says.

So Whitehead thought he would create some work for himself by producing a play. The Theater Guild, he heard, had dropped plans to produce "Medea." "So I thought, 'Well, why not read it?' " says Whitehead. "And I got a copy at a bookshop, and thought it was incredibly exciting and simple, and I thought, 'I wonder if I could ever get this damn thing on.' "

His next step was to call Judith Anderson. The play had been dedicated to her, and Whitehead naturally wondered if she would care to play the part. Discovering that she would, he was encouraged to approach John Gielgud. He did not know Gielgud any more than he had known Anderson, but he had been bowled over by Gielgud's production of "The Importance of Being Earnest," and thought this might be the man to direct "Medea." So he went backstage, "simply knocked on the door," and gave Gielgud a copy of the play. Initially, Gielgud said he wouldn't have the time to direct "Medea," but a few months later he called back to say that because of a change in his schedule he would have the time, after all.

With the names Anderson and Gielgud in tow, Whitehead decided to do the play on Broadway, although, he recalls, "everyone said it was a very worthwhile idea, but it wasn't a Broadway show."

Everyone, of course, was wrong, as everyone often is. "Medea" opened in October 1947, and "suddenly it was one of those marvelous things where people are buying tickets," says Whitehead. Nor was the success purely commercial. "Miss Anderson," wrote Irwin Shaw in the New Republic, "turns her back on all the restrained traditions of modern naturalistic acting, of which she is past-mistress, and gives us an hour and a half of unrelenting violence . . . She rants; she wails; she writhes in agony; she sneers most broadly; she whispers and shouts across the full octaves of her voice. By being resolutely old-fashioned, Miss Anderson brings a fresh dramatic freedom to our stage."

The producers, Shaw continued, "must be complimented on their courage in hurling this work against the commercial walls of Broadway." But there was a sour note in the triumph. After a year's run in New York, Whitehead and Anderson had a falling-out, and he farmed the show out to producer Guthrie McLintic for the extensive post-Broadway tour. "We didn't talk for a number of years," says Whitehead, who, in more recent times, has been the New York partner of the Kennedy Center's Roger Stevens and an important producer in his own right.

Dissolve to 1956. A young Australian actress named Zoe Caldwell wins a minor part in the premiere production of the Elizabethan Trust, which is to be a national, state-supported theater consortium. The production was "Medea." A cadre of stars--including, of course, Judith Anderson--had been imported to launch the new venture with a "great glorious bang," according to Caldwell. But the supporting players were chosen from local talent.

Caldwell played the Second Woman of Corinth. "We were all dreadful," she says. "But Judith was there, and I was deeply, deeply affected by her."

Dissolve to 1979. That is when Anderson, living in semi-retirement on the California coast, thought up the idea of doing "Medea" again to help raise money for the preservation of Robinson Jeffers' house--Tor House--in Carmel, Calif. She had seen Caldwell play Sara Bernhardt on TV, and was "madly enthralled by her great, incredible, brilliant artistry." Caldwell was the "only actress who might be able to play 'Medea,' " she thought.

Caldwell was also, by now, married to Robert Whitehead. After moving to the United States and scoring a triumph in the play "The Prime of Miss Jean Brodie," she had married, had children, and, she says, taken a long sabbatical from acting to attend to "the whole business of being a wife and mum. I just hung in with the boys to make sure that they grew into reasonably solid citizens."

In deference to their past disagreements, Anderson did not call Whitehead directly about her "Medea" idea. Instead, an official of the Jeffers Museum contacted him and advanced the plan without mentioning Anderson's name. Whitehead, intrigued, gave a copy of the play to his wife, who read it and had, at first, a negative response. "I felt it was Judith's play, and it was something I didn't understand totally," she says. "Then Robert began to talk to me about her Medea in deeply human terms," and finally Caldwell told him: "I think I can play that woman. Let's try it."

Whitehead has done very little directing in his career, but he decided to direct as well as produce this "Medea," and to launch it at the Jeffers Museum--outdoors. Toward that end, he arranged to visit the museum in January 1981, taking advantage of a prior trip to Los Angeles with Katharine Hepburn and "West Side Waltz." That was when he received word that Anderson wanted to see him, and could he and Caldwell stop off in Santa Barbara on their way to Carmel?

So after more than 30 years of not communicating, Whitehead and Anderson talked again, and Anderson disclosed the motive behind her invitation. She wanted to take an active part in the new production. To be specific, she wanted to play the part of the nurse.

Both Whitehead and Caldwell were "terrified" by the idea. Caldwell thought, "There's no way I can do the play with Judith there." But they talked about it "over a couple of margaritas," and Anderson asked them: "Who on earth could you get who could play the nurse better than I can?" That, according to Whitehead and Caldwell, was the decisive argument.

As the plans went forward, the new "Medea," like the original, became more ambitious. The outdoor production in Carmel was dropped in favor of an indoor one at the Kennedy Center, preceded by a two-week tryout at the University of Tennessee in Knoxville. There are no current plans for the production after it closes here April 10, but Whitehead has a gut feeling (in which the women's liberation movement certainly figures) that the play "should have even more of an impact today." (The success of "The Greeks," a Royal Shakespeare Company compendium of works dealing with the Trojan War, could lend further aid and comfort to anyone hoping for a revival of interest in Greek tragedy.)

Now that the Whitehead/Caldwell/Anderson team has had several weeks of rehearsing and performing, the parties have reached certain conclusions. Caldwell has not only grown used to the idea of acting in Dame Judith's shadow, but positively effusive about it. "I think it's terribly important for actors to have a chance to work with other actors who have become part of their tradition," she says. "It's like life, death and rebirth . . . I'm an extension of Judith in the play."

Whitehead, while stressing that this won't be a copy of the original "Medea," says he and Anderson have "achieved a friendship that makes me feel all that I lost during those 30 years."

And Anderson, who has never had a child, says, "I'm going to have one now."