Offstage, she usually dresses all in black. Today, she's wearing a black coat, black slacks, black sweater over black blouse and a black watchband. Her eyes are brown, but a triangular wedge of black darkens the left one. With her sharp nose, her long neck and her pale complexion, she resembles a Toulouse-Lautrec print.

On stage, however, Australian-born actress Zoe Caldwell, three times a Tony winner, goes from black and white to living color. She can be -- and has been -- just about everybody: Medea, Mary Tyrone, Cleopatra, Miss Jean Brodie, St. Joan, Colette and Eve. Beginning tonight in the Kennedy Center's Terrace Theater, she will be Lillian Hellman.

The occasion is "Lillian," a new one-woman show by William Luce, who fashioned "The Belle of Amherst" out of the life and poetry of Emily Dickinson. "Lillian" is based on the autobiographical writings of a woman who was as celebrated for her plays ("The Little Foxes," "Watch on the Rhine," "The Children's Hour") as she was for her stormy relationship with detective writer Dashiell Hammett and her refusal to bow before the House Committee on Un-American Activities and Sen. Joseph McCarthy.

"It really has been the most difficult thing I've ever done," Caldwell says, settling into a leather sofa (black) in the office of her husband, producer Robert Whitehead, who is also directing "Lillian." "I had morning sickness every day of rehearsals. Ask Robert! There was something in me that just didn't want to give myself over to Lillian."

Fifteen stories below, the neon signs of Times Square are taking over for the fading afternoon light and the muffled sound of traffic drifts up and in through gray windows. No one has bothered to turn on the office lights. Normally, Caldwell has the energy of 15 fire engines, but the dusk and thoughts of Hellman seem to have brought out her reflective side. You even have to ask her to speak up.

"Oh, heavens! I've never had that problem before," she says apologetically, drawing herself up ramrod straight and clearing her throat.

"The play is set in 1961 in the anteroom of a hospital, two hours before Dash dies, and the whole evening has to be supported by her emotional response to his dying," she continues. "So it isn't a one-woman show where you go out and tell a lot of stories and jokes. To do it, I have to be totally inhabited by Lillian. I know that sounds like spooky stuff. But it really was most painful."

For months, she pored over Hellman's writings, scrutinized her on videotape, talked with anyone who had a firsthand anecdote or impression. She even took up cigarettes again, since "it seemed like Lillian always had smoke somewhere around her." But for the longest time, she couldn't find what she calls "the clinker."

The clinker?

"It's what I have to find in order to play any part -- the thing that sets a person off from everyone else, forms him, makes him vulnerable," she explains. "Everbody has a clinker. It usually turns up quite early in life. Whatever happens later, you can trace it back to the clinker. But in Lillian's case, I couldn't find it.

"I kept saying to Robert, 'Everyone talks about Lillian's femininity.' And she was deeply feminine, despite this image people have of her as a tough, smoking lady. She was a flirtatious southern belle. She spent a lot of money on clothes. She always had her nails and her hair done. And yet there in the middle of her face was this nose -- not just the nose she was born with, but this bashed-up nose. A woman who spends such an inordinate amount of money on her personal appearance in this day and age would have that nose tended to. But she never did. In all her photographs, it's like this great badge of courage she wears. That's the clinker!"

Caldwell claps her hands triumphantly -- a sudden Sherlock, laying out the evidence that unlocks the puzzle.

"Well, when I went back to her writings, I discovered that in puberty, Lillian's great love was her father -- a witty, liberal, good-looking man. She was the only daughter. Big connection! When she was 14, she saw her father kiss this giggling, faded, sexy woman and then get into a cab with her. Lillian was in such a rage of impotence toward her father -- and feeling such pity and contempt for her mother -- that she climbed to the top of a fig tree, her secret hiding place, threw herself from it and broke her nose.

"Like a lot of southern people, she had a black nurse, Sophronia, who gave her nose a prod, which must have hurt terribly, bandaged it up and put her to bed. Sophronia was a great moral force, and when she found out why Lillian had thrown herself from the tree, she said, 'Don't you tell anyone about your father. If people ask you about your nose, tell them you fell in the street. Don't you go through life making bad trouble for people.' Those were the words -- 'making bad trouble for people.' Years later, when Lillian wrote her letter to the House Un-American Activities Committee, she said, 'I will not, now or in the future, make bad trouble for other people.' Yes, the very same words!

"That unlocked her for me. Lillian was abrasive and outspoken. But the core of her, I think, was that she deliberately tried not to make 'bad trouble for people.' That helped me understand all the despair and disturbance she suffered, for example, in her sexual relationship with Dash, who had a lot of other ladies. It helped explain her feeling for the blacks. She had decency. And in this day when everyone is talking about morality, just plain decency is kind of swell."

She pauses to inhale a cigarette. "She also had a lot of enemies and I suppose I'll get flack from some, saying how dare I make people love Lillian. But I just wish we had a few more Lillians. What we're lacking nowadays is individuality. Oh, people are being individual to a fare-thee-well, showing up in all sorts of fancy dress, so that they all look alike they're so individual. I don't mean that. I mean the ability to think individually, to be bright but also very vulnerable, which is the double whammy."

Caldwell is widely thought to be one of the best actresses working in the American theater today. Christopher Plummer, her sometime leading man, once called her "the perfect chameleon." Consummate of craft, rigorous of discipline, her performances invariably transcend her modest physical stature. Even in the hush that has overtaken her this afternoon, you can sense the theatricality in her fingertips, hear it in the tautness of her articulation, seemingly coiled and ready to pounce on the first unsuspecting word.

It all stems, she believes, from her clinker -- the small motor skills disability she's had since childhood. She cannot write legibly -- her signature looks like a Slinky -- nor can she sew on a button. Any task that requires tiny, delicate finger movements defeats her. "But very early on," she explains, "I discovered I could move, I could speak. I communicated with grand, physical gestures and this expansive vocal quality."

Her father was a plumber in Melbourne, and her mother had long since retired from minor roles in Gilbert and Sullivan operettas. But they recognized a dramatic sensibility in their child, and let her attend elocution school. By age 9, she was on the professional stage. In 1956, when Judith Anderson toured Australia in "Medea," Caldwell was cast -- prophetically, as it turned out -- as part of the chorus.

On scholarship, she left for England to play walk-ons and understudy at Stratford-on-Avon. By her second season there, she was appearing as Cordelia in "Lear," Helena in "All's Well That Ends Well" and Bianca in "Othello," alongside Charles Laughton and Dame Edith Evans. It was merely the start of an enviable list of classical credits.

"I'm a gypsy and I've gone wherever my career took me," she says. "I've always been afraid of being a big fish in a small pond, so whenever I felt too comfortable, I'd cut and run. I'd take the first job that was offered me. So I played a lot of parts I wasn't ready for. That didn't matter. I never asked who the director was, where the theater was or what I was going to wear. I just said yes, so I was never out of work. But I've acted in some pretty strange places."

She leaped the ocean to be part of the Stratford Shakespeare Festival in Ontario, Canada; jumped again to act with the original company at the Tyrone Guthrie Theatre in Minneapolis; and continued jumping -- from the Guthrie to the Manitoba Theatre Center; to the Goodman Theater in Chicago; back to the Guthrie again. Broadway never saw her until 1966. As Anne Bancroft's understudy in "The Devils," she was rushed into the second act when the star accidentally injured her back. Later that year, Tennessee Williams' short-lived but vividly surrealistic "Slapstick Tragedy" brought Caldwell her first Tony.

In 1968, she trilled the passionate credo of Miss Jean Brodie -- "Give me a girl at her impressionable age and she's mine for life" -- and won her second Tony. Accentuating the writhing sexuality and animalistic nature of Medea in the Kennedy Center's production of the Greek classic, she pocketed a third in 1982.

In the process, she has amassed both a sheaf of laudatory notices and what is perhaps the rudest pan on record. The latter was filed by John Simon, who left the off-Broadway production of "Colette" in a particularly acute state of bile, having found Caldwell "unattractive in every part of the face, body and limbs, though I must admit I have not examined her teeth." The climax of that biographical play called upon Caldwell to bare her left breast. "The sight," Simon screeched, "is almost enough to drive the heterosexual third of the audience screaming into the camp of the majority."

"Of course, something like that hurts," Caldwell acknowledges. "But nothing beyond hurt. You're not paralyzed by a critic like John Simon. You have to respect someone's opinion before you can be paralyzed by it. By a Harold Clurman, a Brooks Atkinson, a Walter Kerr, I could be paralyzed. From what people tell me, Simon apparently takes after me everytime I come up to bat. I don't read him, so I don't know. I'm really not very interested in what John Simon has to say about anything."

At 36 (she is now 52), Caldwell married Whitehead and voluntarily threw her career into low gear. They have two sons -- Charles, 13, and Sam, 16 -- and for a while Caldwell "just hung in there with the boys to make sure they grew into reasonably solid citizens." The family lives in Pound Ridge, N.Y., in the midst of 125 acres of woodland, and maintains "a pad, nothing so grand as a pied-a -terre" in Manhattan.

"People must think I'm tempestous and strong," Caldwell says. "They're always saying to Robert, 'Must be very interesting, but very difficult to live with Zoe .' But I'm not that way at all. Of course, I've been a theater person all my life, and will be as long as I live. It's what keeps me balanced. Acting gives me a certain calm. When I go too long without doing it, I need something to [siphon] off the passion that's contained in me. So I clean the hell out of the house. I cook. Or I complain about the disorganization of the boys' room.

"But I think I'm a better mother, because I also work. Otherwise, I would need to speak too often and too loudly. I'd be terrible at the PTA meetings."