Mr. Levinson, known to his friends as Bob, liked to swap information with journalists interested in espionage and intrigue. Some of his tips paid off; others were wild goose chases. Brian Ross, the chief investigative correspondent for ABC News, who knew Mr. Levinson for decades, said he turned up at ABC headquarters before his disappearance with what sounded like a major scoop.

Mr. Levinson told him his sources had located a major Qaeda operative in Venezuela and were observing the man going into a local mosque twice a day. ABC News dispatched an employee to Venezuela, where he rented a room at a hotel across the street from the mosque and waited for the terrorist to appear.

“We spent a week there staking it out,” Mr. Ross said not long ago. “Nothing happened.”

Mr. Levinson told his children that he knew from the age of 8 that he wanted to be an F.B.I. agent. His epiphany came, he said, while watching a movie called “The House on 92nd Street,” a low-budget thriller about a college student who goes undercover for the F.B.I. during World War II to break up a Nazi spy ring.

As a teenager, Mr. Levinson liked to hang out with friends in the attic of his family’s home in New Hyde Park acting out courtroom dramas. For dialogue, they used transcripts from real trials typed up by his mother, who was a part-time court stenographer.

From the start of his career, Mr. Levinson saw himself as a collector of informants, someone skilled in extracting information from people eager to catch a break from the law or in need of a favor, like a United States visa. By the late 1970s, he had his dream job, working in the F.B.I.’s New York office, helping to coordinate intelligence about the Mafia gathered by agents in the metropolitan area.