It's a literary mystery. A mystery, that is, involving a man of letters, one who made a very big splash back in '89 -- that would be 1789. British readers were riveted by his first-person account of being kidnapped and enslaved at age 11 and dragged from Nigeria to the New World in a horror-filled slave ship.

Olaudah Equiano's tale has long been viewed as the definitive account of the infamous Middle Passage, one of the very first slave narratives, an accounting that gave the fledgling abolitionist movement a ringing moral authority.

Except it might not be true.

Therein lies the mystery: Because if the man who penned "The Interesting Narrative of the Life of Olaudah Equiano, or Gustavus Vassa, the African, Written by Himself" was not African-born, but rather an African American born in South Carolina -- as Vincent Carretta, a University of Maryland scholar, suggests -- then who was he? Where did he learn to speak fluent Igbo? And how did he get such excruciating details about life aboard an 18th-century slave ship?

The air soon became unfit for respiration, from a variety of loathsome smells, and brought on a sickness among the slaves, of which many died, thus falling victims to the improvident avarice, as I may call it, of their purchasers. This wretched situation was again aggravated by the galling of the chains. . . . The shrieks of the women, and the groans of the dying, rendered the whole a scene of horror almost inconceivable.

Therein, too, lies the controversy: Carretta's findings, detailed in his biography of Equiano in bookstores next month, have sparked a firestorm in academic circles, particularly among those who have long considered Equiano, on the weight of his autobiography, the "black Ben Franklin." (Actually, since Equiano's was published first, Carretta argues that Franklin should be dubbed the "White Equiano.")

No one disputes that Equiano was the ultimate self-made man, erudite, intellectual, a slave who bought his own freedom, became a seaman, ran a plantation in Central America where he bought and sold slaves, had a change of heart and became an abolitionist, and later, while living in England, made a mint off his self-published memoirs, passing on a fortune to his biracial British daughter.

There is, however, considerable dispute about the significance of two British documents Carretta has discovered: a 1759 baptismal record and a 1773 ship's muster, which both list Equiano's birthplace as South Carolina.

"I don't question [Carretta's] research," says Paul E. Lovejoy, Canada Research Chair in African Diaspora History at Toronto's York University, who is writing an article about Equiano.

"What I question is the conclusion he's reached. I just think there's an alternate interpretation," one that does not preclude an African birth, Lovejoy says. Mistakes are often made with records, the professor notes: During Equiano's lifetime, after enemies questioned his authenticity, one of the witnesses who vouched for his African birth was his godmother -- the same person who is listed on his baptismal record as vouching for his South Carolina origins.

Counters Carretta: "This is all Joe Friday 'Dragnet,' just the facts, ma'am" research.

Things began around 15 years ago, when Carretta, a professor of English at Maryland who had long been enamored of Equiano, ever since he started teaching his autobiography to undergrads, hopped a plane to England and started hunting. At Westminster Abbey, he stumbled on the documents that recast Equiano's beginnings in a completely unexpected light.

"No one had ever looked at his naval records," Carretta says, still sounding a little surprised. "He tells us the month and year and place he was baptized.

"I was indeed shocked. I said, 'This does not make sense, this shouldn't be. What do I do with it?' "

Carretta decided to test the waters: He edited a new edition of "The Interesting Narrative" for Penguin in 1995 -- and listed his discovery in a footnote. No one noticed.

So in 1999, feeling a little more adventurous, he printed his findings in a history journal, Slavery and Abolition. People noticed.

Some academics in African American studies saw Carretta's findings as an attempt to discredit Equiano, to depict him as the pawn of white abolitionists.

At an academic conference in 2003, scholars debated whether Equiano's claims of his origins were "most likely rhetorical exercises," according to the Chronicle of Higher Education, which first reported on Carretta's biography.

Carretta sees his findings as a twist in the narrative, one that intrigues but, he argues, in no way diminishes Equiano's authority.

"No one raises these questions about Ben Franklin," says Carretta, whose book is titled "Equiano, the African: Biography of a Self-Made Man."

"No one believes Franklin's biography is absolutely unvarnished, true. Everyone selects, elaborates, enhances, embroiders. We expect that. To not, is to assume that someone is a transparent auto-Dictaphone, and can't shape anything, which is more demeaning.

"My Equiano is a literary genius. Other people's Equiano is more like a literary tape recorder: He says what he says."

University of Maryland scholar Vincent Carretta's book "Equiano, the African" questions the accuracy of assertions in a famous slave narrative.