BOSTON — IT was a subtle distinction, for a psychopath.

“I loved her,” Stevie “The Rifleman” Flemmi said of his onetime girlfriend, Debbie Davis, a sparkling blond Farrah Fawcett look-alike, “but I was not in love with her.”That’s fortunate, since it would have made it ever so much harder to plan the 26-year-old’s 1981 murder, look into her eyes as she was strangled in your parents’ house, strip off her clothes, yank out her teeth and then dig her grave in marshland by the Neponset River.

Deterring identification was his specialty. He was the one who pulled the teeth out of corpses. He was so meticulous at his job that his partner in the Winter Hill gang, Whitey Bulger, had his girlfriend, the dental hygienist, get Flemmi a proper set of extraction tools.

It’s hard to imagine now, seeing the two old wiseguys snarling expletives at each other in court — Dracula battling Frankenstein, as one Boston lawyer told The Associated Press. The 79-year-old Flemmi is hard of hearing and wears a cheesy windbreaker. But back in the day, Stevie and Whitey fancied themselves rat-a-tat-tat Romeos. Flemmi has said he was more adept with the ladies, but then, his taste ran to under-age girls.

The primary triangle in the Winter Hill gang involved Flemmi, Bulger and an F.B.I. agent named John Connolly.

Whitey and Stevie got close in 1974, drawn together, funnily enough, by their clean-living ways. “He didn’t drink, he didn’t smoke, he worked out regularly,” said Flemmi, who described their relationship as “strictly criminal.”And, though Bulger risibly keeps denying it, he worked as a rat for Connolly, another Southie who had grown up in awe of Whitey and his political kingpin brother, Billy. Connolly and Bulger took walks on the beach, and Bulger gave the F.B.I. agent a diamond ring for his girlfriend and envelopes full of cash for vacations and at Christmas.

In return for being that most loathed thing in Irish culture, an informant, and providing information about the Mafia, Bulger got protection and tips from Connolly. That allowed him to play Jimmy Cagney, dispatching underworld enemies. He also got the signal to go on the lam.

“It’s always good to have connections in law enforcement” to survive, Flemmi said, noting that they had about a half-dozen F.B.I. agents on the payroll.

“Zip” Connolly began swanning around spending his ill-gotten gains — $230,000 over the years — on flashy clothes and a boat.

Whitey made the agent sell the boat, and he cut back on Zip’s cash payments. “If he needed it,” Flemmi said, “he was going to have to explain what he wanted to do with it.”Flemmi was also a rat, recruited even earlier by a different corrupt F.B.I. agent. The 83-year-old Bulger, neat and upright in jeans and sneakers, must have been seething as his former “associate” fingered him for his “numerous, numerous” meetings with the F.B.I., even though everyone already regards him as a cheese-eating rat fink, the inspiration for Jack Nicholson’s character in “The Departed.”Then there was the other deadly B-movie triangle. The 38-year-old Flemmi met Debbie Davis, who was working for a fence, when she was married and 17. Both got divorces, and Flemmi lavished her with a Mercedes, jewelry and vacations.

Whitey — “a low-key sort of a guy,” according to Stevie — was once more upset by the ostentation. And the competition.

“He wasn’t too happy with my relationship with her because it started to interfere with my business,” Flemmi said. “She required a lot of attention. She was a young girl.”Whitey called one night to summon Stevie while they were out celebrating Debbie’s birthday. “She said, ‘You meet him all the time during the day, why do you have to meet him now?’ ” Flemmi recalled.

Trying to assuage her, Flemmi “blurted out inadvertently” that they needed to see their F.B.I. connection, Connolly.

Flemmi said that when Whitey learned of the slip, he ordered her killed because they owed it to Connolly.

“I couldn’t do it,” Flemmi said. “He knew it. He says, ‘I’ll take care of it.’ ” They continued to work together until 1994, but the sour taste lingered. “It affected me, and it’s going to affect me till the day I die,” Flemmi said.

Stevie lured Debbie to the house in South Boston — facing Billy Bulger’s house — under the pretext of wanting decorating tips. Whitey claims he would no more kill a woman than be a rat. But Flemmi says Bulger grabbed Debbie by the neck as soon as they walked in and strangled her “all the way down to the basement.”One juror cried as Flemmi told the grisly tale of wrapping Debbie in a tarp, throwing her in the trunk and driving her to Quincy.

“I dug the hole,” Flemmi said, while Whitey sat on the side and watched. In a weary, bitter tone, the Rifleman concluded, “That’s what he does.”