The fund-raiser was small and modest, about 40 people sipping punch and sampling desserts in October on the pool-side patio of Atlanta City Council President Marvin Arrington. D.C. Mayor Marion Barry, candidate for reelection, was the visiting guest of honor.

The party sponsors were Arrington, Atlanta Mayor Andrew Young, a few businessmen and -- it turns out -- the FBI.

Right on the printed invitation beneath the names of Young and Arrington was the name of "Leonard Carey," the sponsor who was a spy. Posing for 17 months as a smooth-talking consultant, Carey was an undercover FBI agent who penetrated the close-knit world of District government officials and city contractors.

The fund-raiser was a showcase for Carey's ability to blend quickly into the social and business fabric of Washington politics and contracting -- a knack that allowed him to play a central role in a federal probe of city contracting that was disclosed May 22.

Identifying himself as an Atlanta businessman, Carey was introduced to District contractors in early 1986. With them, he talked a good game, played an excellent hand of bridge, enjoyed golf and by October 1986 was sponsoring an event for the city's highest official. Before the FBI sting operation was over, Carey wound up contributing $1,500 to Barry's reelection fund.

"That guy from the FBI makes Kojak and Columbo look like bums," said Warren E. Barge Jr., a Detroit area businessman who formed a partnership with Carey, unaware that he was getting into business with the FBI. "He's so good. Who's that guy who put on the dress in the movies? Dustin Hoffman? That's it. Yeah, he makes Hoffman look like a dog."

At least one Atlanta official was incredulous that an unknown figure with no ties to the District could have pulled off the feat.

"That is phenomenal," said the official, who attended the Atlanta fund-raiser and could hardly believe that the Leonard Carey listed on the invitation turned out to be an FBI agent listed later in court records as Roy Leonard Carroll. "You mean nobody {in city government} ever called Atlanta and said, 'Have you done business with this guy?' "

But those who watched Carey operate, and one source who knows him in real life, were less surprised. The source described Carey as an experienced undercover agent, a glib talker and slick dresser who "has done this kind of thing before," although not in the area of alleged D.C. government corruption.

"He could sell ice to the Eskimos," the source said.

But now the enthusiasm with which he was greeted appears to be turning into a deepening case of amnesia.

One city contractor could recall only that Carey was "a southerner." A high-level city official seemed to remember that "he was white." And a second city official said wryly, "Everybody is trying to remember where they met him and what they said to him."

Law enforcement officials are just as reluctant to discuss Carey, who remains an enigmatic figure.

Carey's introduction to the D.C. business world, in January 1986, was to Barge.

Brent Kynoch, president of Asbestos Abatement Services, a local firm, arranged the meeting at the behest of federal authorities after Kynoch alleged that Barge had approached him and solicited money in return for help in obtaining city contracts.

Barge later denied that, saying he called Kynoch to suggest that Kynoch needed minority participation in his firm to obtain District government business. Kynoch, Barge said, "blew it all out of proportion."

At Kynoch's Northwest Washington office, Carey was introduced to Barge, 43, as "a big guy that finances" Kynoch's company, according to Barge. Carey, a short, dark-haired man in his early thirties, greeted Barge effusively. "I like the way you dress," Barge remembers him saying. "I like the way you talk. Maybe we could put a joint venture together."

Barge, a man who once owned two Rolls-Royces, and Carey, who spoke often of his "Atlanta money," got along fine. "Everything that Barge said, {Carey} tried to top," recalled a source who observed them. "It was like two little kids. If one can jump over the fire hydrant, the other can jump over the wall."

On July 30, 1986, incorporation papers for B&C Management Consultants were filed, and subsequently Barge and Carey's firm moved into a fourth-floor office at 1825 I St. in the International Square building, where everything, according to Barge, was "first class."

His role completed, Kynoch dropped out of the picture. Barge, Carey and the firm immediately began popping up in many of the right places.

On July 30, the firm showed up on a list of sponsors of a Business for Barry fund-raiser held in the District.

Later, Carey joined in at bridge parties at the home of Alexis H. Roberson, director of the D.C. Department of Employment Services, according to one city official. Roberson, asked last week about Carey, declined to comment.

In early fall, Barge and others dined with Barry aide David E. Rivers at The Broker, a Capitol Hill restaurant known for its continental cuisine and clientele of lobbyists and government officials, Barge said.

After a night of "drinking and celebrating," Barge said, Rivers charged the cost of the meal, about $400, to his American Express card. Carey, he said, later gave Rivers western-style boots "out of gratitude for his picking up such a large check." Barge said he "okayed" the gift, but he would not say whether Carey was at the dinner.

Western-style boots are a key element in the federal probe. Federal investigators are trying to determine whether Rivers, the former head of the Department of Human Services, received boots in return for steering contracts from the agency to B&C. Two pairs of western boots, secretly inscribed with Carey's FBI credential number, were confiscated from Rivers' house during an FBI search on May 22, officials said.

Rivers has denied any wrongdoing. No charges have been filed in the contracting probe.

In October, Carey and Barge received their first city contract, an energy audit of Forest Haven, the District's facility for the mentally retarded in Laurel. In March, they landed a second energy audit, this one at St. Elizabeths.

Then, on May 22, the partnership between two men who could sell just about anything to anyone ended abruptly. Carey turned up at the Omni Shoreham Hotel, where Barge was staying, Barge recalled.

"He knocked on the door and opened his badge up," said Barge. "He said he was an FBI agent . . . . I was shocked. I said, 'Okay, what can you do to me next?' "

Amid a flurry of subpoenas and searches that day, "Leonard Carey" retreated behind the doors of the FBI's Washington field office.

On May 31, Carey's lease at the Oakwood Apartment complex in Alexandria ended. Someone else moved in to the two-bedroom apartment Carey once listed as his home.