NEW YORK — As folks might say back in Atlanta, where she hails from, Brenda Leigh Johnson is a caution. She’s a stitch. She’s a sight.Crime-busting heroine of TNT’s “The Closer,” Brenda now calls Los Angeles home. As boss of a special LAPD unit charged with cracking high-profile murder cases, she makes the city safer one dramatic confession at a time.

But her procedures aren’t always by the book. Nor consistent. Brenda can be charming. She can be blunt. She can be a pain in the patootie, punctuated with her sugary, all-purpose catch phrase, “Thahhnk-yeewwwwww very much!”

“She’s a bundle of contradictions,” sums up Kyra Sedgwick, speaking in a voice unstuck from Brenda’s honeycombed Southern accent.

“From the moment she wakes up in the morning till she goes to sleep at night, everything outside of work is full of mistakes,” Sedgwick says. “In her work she’s just an absolute genius, but her personal life is sort of a mess.

“That’s such an intriguing character to play!”

Sedgwick isn’t the only one intrigued by Brenda. Last season, a hefty 6.6 million viewers watched each week as Sedgwick sparked her own crime wave with all the scenes she stole.

“The Closer” returns for its third season Monday at 9 p.m. EDT. On this episode (which will air commercial-free and uninterrupted), Brenda leads an investigation into the stabbing murders of a husband and wife and their young daughter.

Their drug-abusing teenage son emerges as the obvious suspect, and Brenda handles him with her shrewd mix of tender and intimidating. By the end of the hour, she has her confession.

But, as Sedgwick notes, Brenda’s personal life puts her on less certain ground. Her beau (Jon Tenney) is pressing for the two of them to ditch her cramped house and find a larger nest to share. But Brenda keeps stalling. Romance makes her nervous. She is alternately confrontative and standoffish with people. She is clumsy with her social skills. Even with a guy she probably loves.

“I just got very lucky,” says Sedgwick, speaking of this juicy role, which continues to flourish thanks to her collaboration with “Closer” creator and executive producer James Duff.

“By this point,” she says, “James and I have a total mind-melt: He is Brenda and I am him, and I am Brenda and he is me. We’re very simpatico about the character.”

For Sedgwick, a favourite quirk is Brenda’s sweet tooth (and her efforts to hide it).

The script for the series’ first episode had her sneaking a RingDing sugar fix.

“When I read that, I was like, `Oh, we HAVE to make food an issue for her!”’ says Sedgwick. “She eats secretly by herself! Instead of having a drink she eats a RingDing! There’s an addictive thing going on there, and it really bothers her that it controls her.”

A beseeching sweet tooth? “I can totally relate,” laughs Sedgwick, though, during an afternoon chat at a mid-Manhattan diner, she’s having only tea (and her figure is clearly unacquainted with overeating).

Production of the L.A.-based “Closer” takes four months, but Sedgwick is spending a brief hiatus back in New York, where she lives with her husband, actor Kevin Bacon, and their teenage son and daughter.

“Kev’s so incredibly happy for me,” she says. “He’s been there for me in the past when I was like, `Boo-hoo, why aren’t I doing better?’ And he would say, ‘Just wait, just wait.’

“Now he can say, `See? I told you!”’

Maybe he said that last January, when, much to her surprise, Sedgwick won the Golden Globe for best actress in a drama.

“Kevin and I have both been through a lot of ups and downs,” she says, “and this is an up. And it keeps getting better.”

Though never a box office draw before “The Closer,” Sedgwick, now 41, had accumulated many solid credits, including the drama “Loverboy” (costarring and co-producing with Bacon, who directed), as well as the HBO film “Something the Lord Made” and TNT’s “Door to Door.”

Her next film will be “The Game Plan,” a comedy costarring The Rock, due out this fall.

But Sedgwick’s first role was in eighth grade, in a school production of “Fiddler on the Roof.”

“I thought, `This is the most happy I’ve ever been,”’ she recalls. “I knew immediately this was what I wanted to do forever. And I was fierce about it: acting camp, acting classes. Then I started working professionally when I was 16,” in the NBC daytime drama “Another World”

Years later, she remembers how, right after the school play her parents told her, “You’re really good.” She believed them.

“But I really didn’t care if I was good or not,” says Sedgwick. “It mattered more to me that I tell the truth. I want my performance to be true to the character.”

That’s the sort of honesty that Brenda would salute.On the Net:

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