As a baby-faced 28-year-old hauled in for fraud, the man sitting in Istanbul police headquarters that August day back in 2001 seemed like just another petty criminal. But then he began to talk, and eight years later, Turkey is talking about little else.

"I've never seen anybody like Tuncay Guney," remembers Ahmet Ihtiyaroglu, an organized-crime interrogator. "It was as if somebody had sent him in to reveal everything."

Held for eight days, Guney listed -- he says under torture -- the names of high-ranking academics, journalists and left-wing nationalist politicians he claimed were members of a terrorist organization. In his house, police found six boxes of documents, some top-secret, to back his allegations.

They called in investigative magistrates. But Guney was gone. Out on bail, he fled to the United States, somehow avoiding a ban on leaving the country.

Almost eight years later, his 2001 testimony is central to a criminal investigation described by some as the most important in Turkey's history and by others as a judicial coup organized by the Islamic-leaning government.

Named after a legend rooted in the Turkish people's Central Asian origins, the Ergenekon case began in June 2007 after police discovered an arms cache in an Istanbul suburb. Now, 86 suspects are beginning their 12th week in court on charges of "attempting to overthrow the government by force." [For background see the Eurasia Insight archive].

On January 7, 40 more men, including two retired four-star generals and Ibrahim Sahin, a former Special Forces police chief, were taken into custody after a coordinated dawn sweep across the country. Two days later, investigators used a sketch they had found at Sahin's house to uncover machine guns, rocket launchers and explosives at a popular picnic spot outside Turkey's capital, Ankara. On January 11, an additional 14 suspects were detained.

"This is a regime change, like in the time of [Ayatollah] Khomeini or Hitler," Deniz Baykal, head of Turkey's chief opposition party protested. Like many authoritarian secularists, he is dismayed by the way on-going investigations have touched the former untouchables of Turkey's still circumscribed democracy. "I sparked a revolution in my country," Tuncay Guney boasts in an e-mail from Toronto, Canada, where he has been seeking asylum since 2004. "The masks fell."

It sounds self-aggrandizing. But Guney has a point.

The names of most of the men and women on trial today in a high-security courthouse outside Istanbul appear in his 2001 deposition. A photograph he sold to the Turkish media in 1997 showing Ibrahim Sahin arm-in-arm with notorious mafia hit-men confirmed beyond doubt senior Turkish officials' links with organized crime. Guney's name appears over 400 times in the 2,450-page Ergenekon indictment.

Yet you only have to watch one of Tuncay Guney's dozens of appearances on Turkish television over the past year to see why so many Turks are so suspicious of him.

Comfortably ensconced in a black leather armchair, clearly enjoying his notoriety, this son of a farmer from a typical Muslim village in northern Anatolia now dresses like an orthodox Jew and claims to be assistant rabbi in a Toronto synagogue unrecognized by Canada's Jewish community.

Interviewed by Newsweek Turkey last November, an evangelist friend who helped him cross over to Canada in 2004, insists he converted Guney to Christianity while he was in the States.

"When you deal with Tuncay Guney you deal with a fundamental dilemma," says Sedat Ergin, editor in chief of centrist daily Milliyet, where Guney briefly worked as a technician in the early 90s. "He is the one who first revealed the Ergenekon organization. Yet at the same time he is a fabricator of tall stories."

In his e-mail, Guney puts his success in gathering the information police found in his house in 2001 down to his skills as an investigative journalist. "I can't say I'm very intelligent, but I work hard," he says. He flatly denies having worked as an informer for one of Turkey's intelligence agencies.

Behic Kilic, who hired Guney in 1995 when he was editor-in-chief of the daily Aksam, doesn't believe him. "He was a nice, naive-looking kid who could barely write an article, but then he began bringing in scoop after scoop," he remembers. "He had connections, no doubt, and I'd hire him again without a second thought."

The question of who Guney was working for has been one of the first victims of the war of media disinformation stirred up by the Ergenekon case.

According to the police, Guney claimed he was working for a powerful military intelligence general now on trial for alleged membership in the Ergenekon conspiracy. There are also hints he may have been working for MIT, Turkey's national intelligence agency. Many secularists, meanwhile, remain convinced Guney is a patsy for a powerful moderate Islamic group they accuse of trying to undermine Turkey's secular system. "Guney is the kind of man every intelligence agency would love to have," says Milliyet's Ergin. "He had this astonishing ability to penetrate any network."

Former acquaintances of Guney -- who describes himself as "a manic collector of people" -- suspect that his strongest card may have been his apparent harmlessness. "I think people let him into their lives because they felt sorry for him," says one journalist who met him in 1994. "He always appeared [to be] a poor, weak character. He wouldn't even have enough money to drink coffee and would always ask people for favors."

As a figure surrounded by intrigue, Guney has upped his game since arriving in Canada. Last October, he told Turkey's top anchorman on live TV that he could prove he was an agent. A month later, he sent magistrates in one southeastern province scurrying to open up wells he claimed contained the bodies of scores of Kurdish dissidents murdered by military police in the 90s.

His garrulousness, and the fact Ergenekon prosecutors e-mailed questions to him recently, rather than calling him back to Turkey for questioning, has convinced many he still has protectors.

In a book about Guney published last November, the Toronto-based journalist Faruk Arslan argued the opposite. Guney's prime aim in stirring up debate inside Turkey is to strengthen his chances of getting asylum. Guney agrees on one point at least. Going back to Turkey, he has written, "would be setting a date with the Angel of Death." But he insists that, in what he describes as "typical Turkish style," he has talked "but not said anything."

"I have been playing with the Turkish media," he says. "And a few witless journalists have fallen for it. I took my revenge. And I got an ego trip."

By turns self-aggrandizing, mournful and rambling, his lengthy email does not read like the work of an all-powerful manipulator. "I feel regret," he writes. "If only I hadn't become a journalist. It got me into trouble. I got caught up in a power struggle. Only shahs can predict when the moves will be made. I cannot, and I am afraid."

An investigative journalist who has followed the Ergenekon case closely, Belma Akcura thinks Guney is "a nobody, out of his depth."

"Reading his police statements, you get the sense he didn't even understand the import of what he was overhearing," she says. "He's a bone the big men have thrown out to the media dogs. I almost feel sorry for him."

Editor of the Toronto-based Turkish newspaper Canada Turk, Hasan Yilmaz, expresses a sentiment shared by many in Turkey: "Tuncay Guney is a man with a thousand faces. Only God knows which is the real one."