NEW YORK -- She arrives at the theater precisely on time, shakes hands warmly, says she's delighted -- but would you mind if she takes a moment, before the notebook is opened and the lens uncapped, to check one detail? She'll only be a second, she just needs to be sure that Tennessee's billing appears as she has specified.

Yes, there's his name above the title: "Tennessee Williams's 'Cat on a Hot Tin Roof.' " "Sometimes it slips," says Maria St. Just, Williams's great friend, co-trustee of his estate and the model, it is said, for his dauntless creation Maggie the Cat.

Wouldn't you like to see the photograph of Tennessee that she's had hung in the lobby? It's just over here to the left. "A lot of young kids, you see, don't even know what Tennessee looked like, and it's so important, don't you agree?" Not that it particularly matters whether you agree or not.

She is properly the Lady St. Just, because she married a British lord, but happily jettisons the cumbersome title ("Call me That Silly Twerp if you want") for journalistic purposes. Anyway, despite her throaty upper-crust inflections, she expresses any and all opinions too robustly to conform to your notion of a politely murmuring Englishwoman. She's Russian by birth and continual proclamation and later, when she orders a drink before dinner, you can see why Williams rather admiringly called her "the raging Tartar."

St. Just: "I'll have a whiskey sour."

Waiter: "On the rocks?"

St. Just: "No rocks at awwll. And none of those other things, either."

For 35 years, the reigning American playwright and the emigre Russian actress traveled together, endured his opening nights together, comforted and badgered one another and, in particular, corresponded. His letters, stitched together with her remembrances, have just been published by Knopf -- "Five O'Clock Angel," the volume's title, was a pet name he used for her -- and generally have been reviewed not only with respect, but with something like relief. Tennessee Williams as the paranoiac craver of pills and alcohol, of critics' benedictions and box office hits, and of an unremitting succession of comely young men -- a portrait that emerged from heedless interviews and posthumous books and from his own discretion-be-damned memoirs -- figures only intermittently between these covers. The letters depict a tenderer Tennessee, a man whom, as her special redemptive mission, St. Just intends to reintroduce to the world.

"His personal image had been ap-pawl-lingly tarnished," St. Just says. "Also his professional image." For after 15 years of unquestioned theatrical artistry -- "The Glass Menagerie," "A Streetcar Named Desire," "Sweet Bird of Youth" -- and accompanying honors, Williams suffered a final two decades of critical rebuff and commercial failure. "I couldn't bear this image for posterity," she says. "Now it doesn't matter what people write." Through the letters (and his journals she plans to publish and the biography she's authorized), she'll show that "he had this courage and purity and indomitability. He never stopped writing."

This campaign of public rehabilitation has become, now that St. Just is a widow and her daughters are grown, the central undertaking of her life. She has, among her and Williams's friends, longtime allies. "Everyone who loved Tennessee will rally around and help in any way we can, because we know what she's doing," says Charles Bowden, who produced several of Williams's plays including "The Night of the Iguana." There are also some skeptics who think she's exaggerating the role she played in Williams's life.

But, bottom line, when attorney John Eastman was drawing up Williams's will in 1980, it was St. Just, along with Eastman himself, whom Williams designated to administer a multi-million-dollar trust on behalf of his sister. While Eastman concentrates on business matters, St. Just will decide, for the foreseeable future, what gets published and what gets produced and by whom. Williams chose St. Just, he told his lawyer, because "he trusted her and she cared."

She still cares, passionately. She wants to preserve Williams's little tin-roofed house in Key West, Fla., as a museum. She means to see his damned or half-forgotten later plays exhumed and performed. She can go suddenly dreamy over one of his turns of phrase, like the title -- "Dead Planet the Moon, I Salute You" -- she says he chose for his journals. "Isn't he incredible?" she exhales. "Can you imagine anything more beautiful?"

She can no longer envision what the life of aspiring actress Maria Britneva might have been like had she not met, at a London party given by Sir John Gielgud in 1948, a quiet man in mismatched socks who became "the best friend anyone could ever have in the world. I felt I was in a state of grace when I was with him."

He asked "Maria darling," in a 1950 letter from New York, to send him an English hair pomade called Floral Cream. He advised her on her fledgling acting career ("You must be realistic about what you should do and what you shouldn't do in the theatre. All the great leading-ladies know these things"). He tried to bolster her after her broken engagement to poet and publisher James Laughlin, and later as her husband suffered through years of depression. Williams told her about his own "crack-up" and failures too, but seemed to strive for a sanguine tone. "Well, love, we're just about the last of the impossible romanticists and we've got to stick together but keep a watch on each other," he wrote in 1972.

Most of St. Just's letters to Williams have been lost or destroyed, a blessing of sorts, she thinks. "Can you imagine my schoolgirl letters? In comparison to his?" But she kept all of his, and after his death in 1983 she began assembling them. "Ah, it was a nightmare," she says emphatically. She says everything emphatically. "I put a lot of letters in books I was reading. They were in my handkerchief drawer. They were scattered over two houses" -- her country estate called Wilbury, so grand that period movies have been filmed there, and a town house in London. "I kept finding bunches of them, with screams of delight."

Rereading and arranging them, however, proved "terribly painful. Tore out my heart, many times. Things I'd forgotten, the beautiful things he said, the protection he offered me. And where was he?"

St. Just can't quite explain "this curious affinity" that bound them; it somehow materialized from shared laughter and a love of Chekhov, from his being "my father-brother figure" (her father was shot in a Soviet purge) and her possibly being a sister figure, she thinks. Williams's beloved sister, Rose, who became mentally ill and was lobotomized in the '30s, lives in an institution in Upstate New York; now 80, she is the beneficiary of the trust that St. Just co-administers.

James Laughlin, who continued to be a close friend to both parties, remembers the young St. Just as "an unsure little girl trying to make her way in the theater" and Williams as achingly shy. They were "two rather vulnerable people kind of clutching together for self-support, and this went on for years. She was the one person who could cheer him up."

They developed "a wonderful companionship, the companionship you evolve after some years in a happy marriage," Charles Bowden observes. "She loved him in the most mature, finest sense of the word love."

Another longtime friend, actress Maureen Stapleton, remembers the way St. Just would imperiously order Williams to change some offending shirt or tie, and how he'd laughingly comply.

But he was less willing or able to accede when St. Just urged him to stop drinking and drugging ("I'd empty all the wine into a flower vahhs"), or opined that a play needed further revision before being produced, or disapproved of one of the young "traveling companions" he was forever discovering, then discarding, in his loneliness after the death of his lover, Frank Merlo. "They were all awful, out for what they could get," she harrumphs now, indignant as ever. "I never met one of them of any quality."

The last years, however gamely Williams lurched toward his typewriter each morning, were grim. The tarnishing that St. Just and her friends so deplore was abetted by its victim, as Williams made public scenes and gave recklessly blunt interviews. "He would be nervous and try to assert himself by saying shocking things," Laughlin says.

He crammed a lot of those shocking things into 1975's "Memoirs," a funny but ultimately dispiriting account that seemed to feature a new sex partner and a new chemical stimulant every 10 pages. It became a bestseller, but the people around him hated it. The memoirs "have his tone but they're dark and one-sided; he was down during that period," says Gore Vidal, a friend of both Williams and St. Just since 1948. "They were perfectly ghastly," declares St. Just, who did not figure prominently therein and, the letters indicate, objected to her omission.

It is an article of faith among Williams's friends that the "Memoirs" manuscript was a mess that was subjected to strenuous editing by Doubleday, which is blamed for the book's "sensationalism." But Kate Medina, who shepherded "Memoirs" and is now a Random House senior editor, says the book received only the standard cutting and revising that any manuscript requires and that "Tennessee worked on it steadily. ... He went over the whole thing with me several times. This was the way he wanted it." Allowing or encouraging such contradictory interpretations of events to flourish seems to have been part of Williams's modus operandi at the time.

Later, after he'd died (he swallowed the plastic cap from a squeeze bottle, the sort used for eye drops, and was asphyxiated), other people's books about Williams began to appear. St. Just loathes one and all, including Donald Spoto's 1985 biography "The Kindness of Strangers," which critics thought generally responsible (Stapleton and Vidal concur), but St. Just finds ap-pawl-ing: more sex, drugs and decline.

Of course, it's not unusual for St. Just to cheerily thrash any opinion that deviates too sharply from hers. Should Williams's Key West house really be a museum? Laughlin, for one, thinks it will merely become a tacky tourist attraction. "Oh, what has Laughlin done for any of his writers?" returns the Raging Tartar, airily dismissing her dear friend, to whom "Five O'Clock Angel" is dedicated. "He never pays them properly."

No wonder St. Just's two daughters convulsed in laughter at a recent London production of a play they'd never seen before, "Cat on a Hot Tin Roof." Maggie the Cat has a drawl and wears a slip, but as Williams wrote to St. Just, "I think a lot of you has gone into the writing of it."

St. Just remembers being "perfectly livid when he threw this play at me and said, 'It's about you.' I stomped into his studio the next morning and said, 'This is outrageous. She isn't even Russian.' I wanted sables; I wanted driving in the snow; I wanted wolves!' " Williams looked crestfallen. "Oh honey," she remembers him saying. "It's your spirit, your tenacity."

Williams had lots of women friends, including a number, biographer Spoto contends, who knew him even longer and had closer and calmer relationships with him than St. Just did. "We would argue," she acknowledges. "I'm very fiery. I speak out."

But in selecting someone to help safeguard his sister and his writing after his death -- an event that Williams always believed imminent -- perhaps he decided against his more temperate friends. Perhaps, of the loyalists who loved him, he simply chose the most ferocious.

Two Williams plays had successful Broadway runs this season. St. Just says she's happy with "Cat," but her real pride was Vanessa Redgrave's "Orpheus Descending." Director Peter Hall, St. Just's friend, "resurrected a completely dead play, a play that never was a success," she crows.

This, of course, is the idea, to stage plays like "Out Cry" and prove that Williams didn't really lose his once-unerring theatrical touch, that he was the victim of bad advice and poor productions. This may or may not prove to be the consensus, but St. Just is soldiering on: A film of "Orpheus Descending" has just been completed, and Hall will direct "The Rose Tattoo" in London next season. St. Just governs these artistic decisions, reviewing every request to stage Tennessee Williams's dramas and turning down a considerable proportion of them.

The trust has also selected Margot Peters, the praised biographer of Charlotte Bronte, to write the authorized Williams biography. Following at a measured pace ("one doesn't want to flood the market," St. Just says) will be a collection of Williams's letters to Laughlin, plus volumes of Williams's journals and unpublished plays.

The time allotted for this mission is not infinite. After Rose Williams's death, the estate will go to the University of the South in Sewanee, Tenn., his grandfather's alma mater; St. Just's role will terminate. Until then she's working feverishly to ensure that "he will be remembered as the greatest poet-playwright in the contemporary theater."

"Maria's made a great contribution to his ongoing career," says Lyle Leverich, a former producer who's worked for years on a massive Williams biography, the first volume of which will be published by Grove Weidenfeld next year. "Death eclipses people in more ways than one; people's literary careers can disappear. But there's hardly a month that Tennessee's name isn't in the papers, and she's largely responsible for that."

St. Just would prefer to ignore Leverich's book, and every book about Tennessee Williams that she and Eastman haven't approved. She's refused to cooperate with any of them and is piqued at friends who have; she won't permit any of these authors to quote from Williams's letters. To her mind all such projects are "pirate" books undertaken by exploiters. (Royalties from "Five O'Clock Angel" will be divided between the trust and St. Just.) "Tennessee's been manipulated all his life," she declares. "I'm the one person who never manipulated him." It seems a great irritant that she can't simply eradicate all unflattering remembrances of this very public person.

But of course, she can't. "Costly Performances," another "personal memoir" of Williams by Bruce Smith, a Chicago public relations man who saw him on and off from 1980 to 1982, was published in a small edition this spring. Smith quotes Williams as complaining about St. Just and makes plain his own dislike, which was roundly reciprocated. "The woman sees herself as sort of the widow of Tennesee Williams, the keeper of the flame," Smith says. "She's always been in the shadows and this is her chance to come out of them."

Spoto, who treated St. Just gently but perfunctorily in his biography, is another skeptic. "She's made a life career out of a passing and very uneven friendship with Tennessee Williams. It's kind of pathetic." The letters in "Five O'Clock Angel," he thinks, offer "a very partial view of Tennessee."

It's somehow fitting that this sort of tug of war continues over Tennessee Williams's memory. He delighted in playing one friend off another, inciting minor snits or major jealousies and watching them unfold. He complained to St. Just about his lovers and, no doubt, to them about her. Seven years after his death, he's still at it. Yet St. Just's jurisdiction over his works and his private papers, which amounts to far greater control than she or any of his other friends and advisers managed to exert while he was alive, suggests that she, not her detractors or competitors, will most influence the way Williams is remembered. He must have wanted it that way.

Vidal, who has also written about Williams in ways that challenge (or at least expand on) the sex-drugs-and-decline image, remembers him as "the funniest man in the world, the best company in the world, which comes through in the book {'Five O'Clock Angel'}, which is why I like the book." Vidal acknowledges that he turned away as Williams's addictions deepened but points out that St. Just never did.

"She's authentic and filled with energy and a great organizer and he needed all that," Vidal says. "People are attracted to people who can do what they can't. She could get him on the plane with a passport in his pocket, and he was often unable to do that for himself."

As Williams's trustee, "she can continue to put the passport in his pocket and get him on the plane. She can continue to do that until she dies."