Focus : Dangerous Liaison : HBO MAKES A FILM ABOUT SINGER PHYLLIS MCGUIRE AND MOBSTER SAM GIANCANA

Phyllis McGuire was a minister’s daughter who shot to fame in the 1950s as leader of the wholesome pop singing group the McGuire Sisters. The group hit the top of the charts with such songs as “Sincerely” and “Sugartime.”

Sam Giancana, the original “Teflon Don,” was one of the most powerful mob bosses of all time. And he loved Hollywood. Opposites attract, as the saying goes, and McGuire and Giancana became lovers in the early 1960s.

Their romance is the subject of HBO’s new movie “Sugartime,” starring John Turturro as Giancana and Mary-Louise Parker as McGuire. John N. Smith (“Dangerous Minds”) directed from a script by Martyn Burke based on the book “Roemer: Man Against the Mob” by William F. Roemer Jr.

Executive producer Gale Anne Hurd (“The Terminator,” “Aliens”) believes audiences will be intrigued with their story. “I think we all have a fascination with the darker side,” she says. “My feeling was that they were both deeply in love and in denial of how their affair would affect their lives. In the end, of course, you can hypothesize: Sam’s connection with Phyllis may have well cost him his life. [Giancana was murdered in 1975.] Phyllis’ involvement with Sam cost her career.”

Retired FBI agent Roemer, who tracked the Chicago-based Giancana from 1957 until 1965, also believes the two loved each other. He’s just never been able to figure out why.

“It’s amazing that it ever took place,” says Roemer, who was creative consultant and has a small part in the film as a CIA agent. “He was just as ugly as he can be and he wasn’t a cultured, refined man. I saw no redeeming human qualities about the guy. We put microphones in his headquarters and listened to him talk all the time. She had everything. She had beauty. She had money. Yet, she fell in love with this gangster. I could never figure it out. I have talked to her several times and she’s a lady. She’s refined and cultured. She’s intelligent and articulate. He was just the opposite.”

Though McGuire was always courteous to the FBI agents tailing her and her mobster boyfriend, the same can’t be said for Giancana. “We lock-stepped him,” Roemer recalls. “He was the only guy in the history of the FBI who we lock-stepped. I would stay half a step behind him and half a step to his left. No matter where he went, I would stay that distance from him. If he went to dinner I would go with him. If he went to the restroom, I would go right up to the next urinal. We got into some situations. “

Roemer’s first face-to-face situation with Giancana was in 1961 at the American Airlines concourse at Chicago’s O’Hare airport. Roemer kept Giancana at bay while the FBI talked to McGuire to see if she would cooperate with them in lieu of being subpoenaed to appear in front of a federal grand jury.

“I’m a former Marine Corps boxing champ,” Roemer says. “We bumped up together physically a couple of times. He started calling me all kinds of names, obscene names. Some of which I had heard in the Marine Corps, but not all of them.”

Roemer lost his composure. “What I did was call all the people all around the airport and I said, ‘Look at this slime. This is Sam Giancana, the boss of the underworld in Chicago. The successor to Al Capone. Just look at this jerk.’ He just put his dirty little finger up against me and said, ‘Roemer, you lit a fire tonight that is never going to go out.’ That was about the first of 50 personal confrontations with Sam.”

McGuire, who lives in Las Vegas and still performs with her sisters, did not cooperate in the production of “Sugartime.”

“They weren’t recorded in stereo,” Hurd explains. “We wanted to have a much lusher instrumental backup [than on the original recordings]. We wanted to make sure that we had sound-alikes, so that Phyllis’ voice--her singing double--sounded like her when she speaks.”

Playing the blond, beautiful McGuire was a welcome change of pace for Parker, especially coming on the heels of her performance as a young woman dying of AIDS in “Boys on the Side.”

“It was really sublime, actually,” Parker says. “I just always look to do something good. And it was really nice that this came along. I got to wear high heels and have my nails done and I didn’t have to die.”

Parker, who watched tapes of McGuire’s performances, tried to capture the “feeling of what she evoked when she was performing with her sisters. It was so particular to that time. And what the music is about and juxtaposed against his life makes it so interesting because the music is so positive. They performed it so guileless and sweetly. If you try to perform anything like that now, people can’t really understand anything so one-dimensionally sweet. Once we got into it, we couldn’t stop singing those songs. We were just in heaven.”

The actress worked with the movie’s makeup artist to create McGuire’s glamorous look. “One thing I was really sort of set on was using the lipsticks that they used at that time,” she says. “There was a time in my life when I was really into the really old Maybelline and Revlon lipsticks. I knew all the names off the top of my head. I wanted to use them because they were what she would have used. They just lent a certain feeling and look which is not modern.”

Parker recalls the first time she was transformed into McGuire she thought she looked “totally goofy. But then you get into it.”

“Sugartime” airs Saturday at 8 p.m. on HBO.