The dubious honor rested upon the tiny town of Mount Rainier for generations. And though it seemed suspicious, no one cared enough to probe the haunting details.

Rather, some considered it a non-issue, and others reveled quietly in the dark mystique it brought to town. And so the legend took on a life of its own: The "true story" that inspired the best-selling novel and subsequent movie, "The Exorcist," was based on the saga of a 14-year-old Mount Rainier boy who was possessed by the Devil in 1949 on Bunker Hill Road.

Or so it went.

But Mark Opsasnick, of Greenbelt, didn't buy that story. A local history buff and self-described investigator of strange phenomena, he launched a private crusade for the "real story" behind the real story of the movie version of "The Exorcist," which was set in Georgetown. After 100 interviews, more than $1,000 in phone bills and a year's worth of research, he has published his 26-page findings in the current issue of Strange Magazine, an obscure journal marketed as "the international magazine of strange phenomena investigation."

Opsasnick's "cold hard facts" are that the allegedly possessed boy was never really possessed at all and--gasp!--that he never lived in Mount Rainier. Opsasnick's expansive, time-intensive, nationwide research all went to prove that the boy lived across off Bladensburg Road in nearby Cottage City and, Opsasnick believes, was not possessed, but merely a prankster.

Opsasnick, a case manager for the Montgomery County Department of Health and Human Services, said, "I realize that a lot of people are not going to care."

Bingo.

Who cared? Not even the man who lives next door to the very house where Opsasnick said the possession supposedly occurred.

"I don't really care about that," the neighbor said. "The whole thing sounds funny to me."

Another Cottage City resident, Efrain Martinez, 46, said, "That just doesn't matter."

While Prince Georgians might not have much interest, the findings apparently do matter to a lot of people beyond the cozy bungalows in Cottage City. For the first time in 10 years, Strange Magazine (current circulation, 12,000) sold out. Said editor and publisher Mark Chorvinsky, 45, of Rockville, "We've been getting e-mail from all over the world, every day."

Strange Magazine made "The Haunted Boy of Cottage City: The Cold Hard Facts Behind the Story That Inspired 'The Exorcist' " available at its Web site. The horror movie has earned a tremendous cult following among people who have been awed by its gory detail since the year it was released, and among teenagers who have just discovered it for the first time.

Nicolai Pawluczkowycz, 13, who lives in Cottage City, is a recent convert. "I'm so into scary stuff," the eighth-grader said on his way home from school. "I think it's so cool. I have the movie, and I watch it all the time. My friends . . . we go up to the Exorcist stairs in Georgetown. It's really fun."

"The Exorcist" won two Academy Awards and to date, 25 years after its release, has grossed more than $165 million, making it the 47th top grossing film of all time, according to Variety Magazine, which tracks the movie industry.

That's why Opsasnick said he had to find the "real story."

"It was my mission. . . . I felt I had a responsibility to set the record straight behind one of the greatest stories of pop culture," he said. "It simply came from a desire to present an accurate record of the facts."

Opsasnick said he is not obsessed with the occult. He is not a religious fanatic. And he has nothing against Cottage City.

"I thought this was a public service," he said. "Mount Rainier can now wash their hands and Cottage City can face its history."

Opsasnick mailed copies of his work to officials in Mount Rainier and Cottage City "for future referance," he said. No response. (Mount Rainier leaders did not return a reporter's phone calls.)

But his article has its supporters. Brooke Kidd, of Mount Rainier, is one of them. "It was always suspicious to me. . . . People could never say exactly where it happened or give many details," said Kidd, 30, director of Joe's Movement Emporium, a nonprofit cultural organization in Mount Ranier. "Most of us really appreciate the effort of that journalist to go through the facts."

Opsasnick said he heard several residents doubt the credibility of the local Exorcist legend while he was doing research in Mount Rainier for his 1997 book, "Capitol Rock," a history of rock music in Washington. That, combined with his already acute interest in local history and strange phenomena, sparked his investigation.

To learn the exact location of the boy's home in Cottage City, Opsasnick connected a tip from a confidant of a priest involved with the exorcism to information from a high school yearbook. He then consulted an old local directory and public records to confirm the Cottage City location.

He knows the boy's name but has never released it. Opsasnick even called him on the phone--he wouldn't speak.

But childhood friends and neighbors told Opsasnick that the boy was a brilliant trickster, who practiced certain pranks to scare his mother and fool neighborhood children.

"There was no possession," Opsasnick concluded. "The kid was just a prankster."

So now what?

The author-investigator concluded: "I accomplished my goal, so there's no reason to go any further."

CAPTION: Mark Opsasnick, at Cottage City Town Hall, says "The Exorcist" drew on a case from Cottage City, not Mount Rainier.