Talk about a killer story line.

For months, a sense of dread has hung over the fictitious town of Salem.

A vicious serial killer is on the loose. So far, seven residents have been brutally murdered. One was shot outside his house. Another was bludgeoned with a brick. A third was stabbed and stuffed into a . . . pinata.

More deaths - violent deaths - are expected.

Though the killer's identity remains a mystery to Salem's spooked citizens, loyal viewers of NBC's daytime soap Days of Our Lives already know the beloved Dr. Marlena Evans (!) is behind the lurid crime spree.

Yes, Lake Worth's own Deidre Hall is The Salem Stalker!

And no one was more surprised than the 1964 Lake Worth High School grad when she got word just before the show's Christmas break.

"I was so flattered," says Hall, 56, who visits Florida about four times a year. "It's a huge compliment to be given the ball to run with it, and it's an extraordinary responsibility."

Although Hall, who has played the compassionate and ethical psychiatrist for more than 20 years, is excited about sinking her teeth into a juicy story arc, she admits her feelings are mixed.

"I feel a little bit unsettled that my character has killed a lot of my best friends," she says. "I feel like I should say, 'I'm so sorry.' "

But there's another reason Hall has mixed feelings. Her contract is up in August. And no talks have been scheduled yet. Is making Marlena a murdering beast a way for the producers to eventually ice Hall's enormously popular - and pricey - character?

"I wish I had a good answer for you," Hall says softly. "Anybody on this show would be crazy to assume they're not going to be killed off. We've seen the best and the brightest leave. Having said that, I don't think they would replace me midstream. My hope is whatever (head writer) Jim Reilly has in mind, somehow he has a redemption for Marlena so the audience can return to loving and trusting her."

Deidre isn't the only Hall who's receiving more attention since it was revealed in the Jan. 28th episode that her character is a homicidal maniac.

Jean Hall, Deidre's 88-year-old mother, has also become something of a local celebrity. Jean lives in a Lantana nursing home with about 300 residents - about 50 of whom, Jean says, avidly follow the show.

"The people in the dining room are now looking at me over their shoulders," she says, laughing. "They're getting quite a kick out of it. They're saying, 'How can Marlena be so confused?' "

Jean wonders, too, about her daughter's, er, Marlena's bizarre behavior.

"I couldn't believe it," says Hall's mom. "I was flabbergasted. But if they can kill her in an airplane and bring her back a month later, they can do anything."

Not all of the show's fans were initially thrilled either. A few days after viewers learned that Marlena was the killer, Jean says, her daughter told her NBC received six bags of mail in protest.

"I thought I was going to have to have someone start my car for a little while," Hall says.

Fans, however, are burning up the show's numerous Web sites to discuss Marlena's heinous crimes and possible motives.

On soapoperafan.com, for instance, one fan theorized that Samantha, Marlena's twin sister, is still alive and is the real killer.

"This would make it possible for Marlena to be one place while Samantha was off killing someone and vice versa," the fan wrote.

On Hall's Web site (marlena.com), one fan admitted to reading up on schizophrenia and dissociative disorders to help her understand why Marlena turned into a lethal killing machine.

Not surprisingly, the Salem Stalker story line has boosted the 39-year-old soap's ratings.

January's big reveal episode, for example, generated the highest overnight ratings since December 2000. Days of Our Lives also finished first in the key daytime demographic of women 18-to-49 for three consecutive weeks, the first time the long-running soap has accomplished that feat in nearly two years.

Even the cast and crew are amped.

"We were all guessing for months and had no idea," Hall says. "We even started a pool. Everybody gave $20 and put their guess in an envelope. Two hairdressers won $400."

Jim Reilly, the show's head writer and consulting producer, isn't surprised by the increased buzz.

"You can go back to the old newspaper line - a headline of dog bites man doesn't sell, but man bites dog does," Reilly explains. "The idea that a character such as Marlena would be a serial killer is so incredibly out of character that people are stunned and it would pique interest."

Reilly says he was in New York recently and, while getting his haircut, his barber got a bit too excited about the juicy plot.

"He said, 'I don't understand . . . why her?' " Reilly remembers. "He was getting so worked up and I had to tell him to keep the scissors away from my hair. It's just a story on television."

A story that's beefing up ratings while also reducing the show's budget. Reilly, however, says the sensational story arc has nothing to do with a top-level order to dump high-priced talent.

"The actors' contracts may have affected when a character died, but they weren't targeted because of their money," Reilly insists. "And the people who died weren't high-ticket talent."

Reilly says viewers can expect a big plot twist in May and more murders.

"Truly shocking victims," he says.

That's good news for Hall, who says she feel energized by playing Marlena.

"I have a lot more freedom," she says. "I have the freedom to be audacious. I can be anything. When I say, 'Honey, the stalker is never going to get you,' it has a whole new meaning. Or when somebody makes me angry and I say, 'I wish you hadn't done that,' it has a whole new meaning. It's hard not to laugh."

Hall certainly laughs a lot about her Florida memories. She moved to Lake Worth with her family at the age of 9 and lived here until she left for Los Angeles to pursue her acting career when she was 18. (She's been married for 11 years to Steve Sohmer, a writer and producer. They have two boys, Tully, 9, and David, 11.)

But Hall's memories remain vivid. She remembers playing the clarinet in the high school band. She remembers the long walks she took with her dad around the lake. She remembers the simple charm of small town life.

"I miss Florida terribly," says Hall. "When you're living there, you don't really appreciate how magical it is. I miss the weather, because there's something about getting off that plane and walking down the terminal and - ahhh!!! - the exhilaration of the warmth in the air and the humidity. It's very freeing to me."

And that's just how Hall feels playing the Salem Stalker.

"I'm having more fun with this part that I've ever had," she says. "It's as good as it gets."

Deidre on Marlena

On why she originally turned down the role: 'When I went to screen test, there was every familiar face I had seen on daytime. When they called me and told me I got the part, I figured if I had gotten this part that must have meant all these other famous people turned it down.'

On what she'd like to change about her character: 'I would like to see her in casual clothes more often. That would be kind of fun.'

On why she left the show in 1987: 'I wanted to experience a nighttime series. I loved doing daytime, but there was such a cachet to nighttime. The truth of the matter is daytime is treated like the poor relations of television.'

On why she came back: 'I thought nighttime would be a better deal and it would be more fun and more exciting, but it wasn't more fun. All it is is a different kind of work.'

On her favorite story line: 'I loved being possessed. Marlena was so nasty. She burned up Christmas trees and tried to drop a chandelier on a couple getting married. She mostly just scared people.'

On the reaction she gets in Florida: 'I'll go to Costco or Toojay's for lunch and it's, "Oh, hi, you're back." It's lovely. I expect it's what celebrities who come from a small town get when they go home. The people know you're there, and they know you'll be back a lot.'

DAZE OF HER LIVES

Marlena has been put through the wringer over the years.

1976: Dr. Marlena Evans first appeared in Salem working at the Bayview Sanitarium.

1977: Committed to a sanitarium after being knocked out and drugged by her twin sister, Samantha (played by real-life sister, Andrea), who then impersonates her!

1979: Weds Don, gets pregnant.

1980: Gives birth to Don Jr. Three months later, he dies from Sudden Infant Death Syndrome.

1981: Raped by Kellam.

1983: After divorcing Don, she weds cop Roman, who was being stalked by Stefano's assassins.

1984: Roman and Marlena became parents of twins.

1986: Marlena goes into a monthlong coma after falling off a building ledge; renews wedding vows with Roman after he was held captive, brainwashed and got a new face; Marlena presumed dead after a bomb blast, but was actually held prisoner by Orpheus.

1991: Returns after a five-year absence during which she was kidnapped and the victim of an induced coma.

1992: Kidnapped - again - for more than a month. This time by a deranged patient.

1993: Baby daughter Isabelle is kidnapped by her . . . half-sister!

1994: Possessed by the devil and called 'The Desecrator!' In private moments, Marlena's eyes glow a fiendish yellow.

1996: Kidnapped (!!!) by Stefano and held in the tunnels of Paris.

1997: Weds John. Later remarries Roman.

2000: Lands a gig as a radio talk show host. A blue-collar version of Marlena named Hattie slowly transforms herself into Marlena.

2004: Revealed as The Salem Stalker - the town's serial killer!