It has been one of the most bizarre literary mysteries in recent memory: Who, exactly, is the novelist JT Leroy? An answer, at long last, is taking shape.

Mr. Leroy's tale was harrowing in its details and uplifting in its arc. He was supposed to have been a young truck-stop prostitute who had escaped rural West Virginia for the dismal life of a homeless San Francisco drug addict. Rescued as a young teenager by a couple named Laura Albert and Geoffrey Knoop and treated by a psychologist, he was able to turn his terrible youth into a thriving career as a writer. JT Leroy has published three critically acclaimed works of fiction noted for their stark portrayal of child prostitution and drug use.

Along the way Mr. Leroy gained the friendship and trust of celebrities and noted writers, who supported his career financially and offered him emotional support when he declared that he was infected with H.I.V. Sales were good, and his books were published around the world. Shy and reclusive, Mr. Leroy, now 25, appeared in public often disguised beneath a wig and sunglasses.

But the young man in the wig and sunglasses, it turns out, is not a man at all. The public role of JT Leroy is played by Savannah Knoop, Geoffrey Knoop's half-sister, who is in her mid-20's.

A photograph of Ms. Knoop at a 2003 opening for a clothing store in San Francisco was discovered online. Five intimates of Mr. Leroy's, including his literary agent, his business manager and the producer of a coming movie based on one of his books, were shown the photograph and identified Ms. Knoop as the person they have known as JT Leroy.

"That's JT Leroy," said Ira Silverberg, Mr. Leroy's literary agent, upon seeing the photograph. Mr. Silverberg said he had met Mr. Leroy a number of times in person. Lilly Bright, a producer of "The Heart Is Deceitful Above All Things," a 2004 film based on Mr. Leroy's 2001 collection of stories, was no less certain. "It's JT Leroy," she said, adding that she had worked with Mr. Leroy extensively on the production.

Nyoka Lowery, a Bay Area hat designer who appears in the photograph alongside the person in question, also said she knew that person well.

"That's Savannah," Ms. Lowery said. She said she has known Ms. Knoop for years. Ms. Lowery identified Ms. Knoop in another photograph online, on the events page of a site for a San Francisco clothing company called Nisa (www.nisasf.com). Umay Mohammed, an owner of Nisa, said in a telephone interview that Savannah Knoop was a friend, and the model on her company's Web site.

Reached by telephone, Ms. Knoop said, "I don't need this in my life right now," before hanging up. She did not respond to several voice-mail messages seeking further comment.

But the discovery of the public face of JT Leroy is only part of the mystery. Still unsettled is the question of who writes under that name.

Writers like Dennis Cooper, Mary Gaitskill and Mary Karr were among those who offered support to Mr. Leroy's literary career, as did several prominent editors at Manhattan publishing houses, and numerous film and pop music celebrities offered him emotional support, including Courtney Love, Tatum O'Neal, Billy Corgan, Shirley Manson and Carrie Fisher.

And of course there were journalists (including, in November 2004, this reporter), who wrote credulous profiles of the successful young writer after interviewing him, often in person. The New York Times even published an article last September under the byline JT Leroy in a Sunday magazine supplement, T: Travel. (A subsequent T: Travel article by Mr. Leroy, about the HBO series "Deadwood," was reassigned by editors when questions about his identity began to surface.)

The unmasking of Ms. Knoop adds to a mounting circumstantial case that Laura Albert is the person who writes as JT Leroy. Pressure to admit the ruse has been building on Ms. Albert since October, when New York magazine published an article that advanced a theory that she was the author of JT Leroy's books.

The New York article, written by Stephen Beachy, portrayed Ms. Albert, 40, and Mr. Knoop, 39, as unfulfilled rock musicians who concocted the character of JT Leroy to gain access first to literary circles and, later, to celebrities. The scheme began, Mr. Beachy wrote, with faxes, e-mail messages and phone calls by Ms. Albert, speaking in a West Virginia accent as JT Leroy. The article also described an acquaintance of Ms. Albert's who said she had asked him to type and fax manuscripts that bore striking thematic similarities to work later published by JT Leroy. When that name became famous, Mr. Beachy theorized, an actor was needed to play JT Leroy in person; he did not know, he wrote, who that actor was.

Mr. Beachy discovered that the advance for Mr. Leroy's first novel, "Sarah," published in 2000, was paid to Laura Albert's sister, JoAnna Albert, and that further payments to JT Leroy were made to a Nevada corporation, Underdogs Inc.

The president of that company, according to public records, is Carolyn F. Albert, Ms. Albert's mother, who lives in Brooklyn Heights. Reached by telephone, she declined to comment. The payment for Mr. Leroy's article in The Times was also made to Underdogs.

After the publication of Mr. Beachy's article, The Times began to examine the circumstances of the T: Travel article written by Mr. Leroy, about a trip to Disneyland Paris. A review of the paperwork accompanying the assignment revealed a discrepancy: the article described four people on the journey. Expense receipts submitted to T: Travel by Mr. Leroy, however, included only an Air France itinerary for three people.

Employees at Disneyland Paris and at two Paris hotels identified Ms. Albert from photographs as the person who presented herself as JT Leroy. Those employees said no one remotely resembling photographs of JT Leroy was traveling with Ms. Albert, who told them her companions were her husband and son. Ms. Albert and Mr. Knoop are the parents of a young son.

When hotel employees told Ms. Albert they were under the impression that JT Leroy was a man, they said, she told them that she had had a sex-change operation three years before and was now a woman.

Ms. Albert did not respond to numerous voice-mail messages requesting comment. Reached by telephone, Mr. Knoop declined to comment.

Peter Cane, a Manhattan lawyer, responded to phone and e-mail messages left at the number and e-mail address JT Leroy provided his editors at The Times.

When The Times asked Mr. Cane to provide his client's passport to confirm his identity and that he had traveled to Europe, Mr. Cane declined. Later, however, he gave this reporter an e-mail statement from JT Leroy in response to questions about Savannah Knoop: "As a transgendered human, subject to attacks," the statement read, "I use stand-ins to protect my identity." In the past, JT Leroy has invoked transgenderism to explain confusion over his identity.

It is unclear what effect the unmasking of Ms. Knoop will have on JT Leroy's readers, who are now faced with the question of whether they have been responding to the books published under that name, or to the story behind them. The identification of Ms. Knoop may also have repercussions for the publishing world; JT Leroy is under contract with Viking for a new novel, and Mr. Silverberg, his agent, said his books were on sale in as many as 20 different countries. Carolyn Coleburn, the director of publicity at Viking, said simply, "We stand by our authors."

But perhaps those most affected by the revelation that Ms. Knoop has been playing the public role of JT Leroy are those who went out of their way to help someone they thought was a troubled young man.

"To present yourself as a person who is dying of AIDS in a culture which has lost so many writers and voices of great meaning, to take advantage of that sympathy and empathy, is the most unfortunate part of all of this," Mr. Silverberg said. "A lot of people believed they were supporting not only a good and innovative and adventurous voice, but that we were supporting a person."