Carol Peletier, played by long-time Atlanta actor Melissa McBride was a bit player on AMC's "The Walking Dead" season one. Meek and withdrawn, she was the battered wife of nasty husband Ed. She looked like potential mincemeat, easily forgotten once chomped on.

But after a zombie kills Ed, Carol volunteered to bash his skull in with a pick ax to ensure he didn't turn into one himself.

Fellow actors and executive producers then watched her hack away with a purpose and intensity that electrified the set.

"The power of her performance blew me away," said Greg Nicotero, an executive producer who has been with the show since its inception. "She has this vulnerability, a sensitivity. She feels like someone you can reach out to."

With the show returning for season five Sunday, McBride is one of just five original actors who remain from season one and her role has been ramped up significantly as the show has gotten ever more popular. It's now the No. 1 show among 18-to-49 year olds, drawing 20 million viewers a week. AMC has already guaranteed "The Walking Dead" a sixth season going into 2016 and is preparing a spinoff.

McBride, a 49-year-old Kentucky native, moved to Atlanta in the mid-1980s and spent the 1990s acting in shows such as "In the Heat of the Night" and "Dawson's Creek." She also acted in oodles of commercials for clients such as Rooms to Go and was a spokeswoman for Ford for a couple of years.

In 2000, she decided to shift gears and become a casting director for Stllwell Casting, where she booked actors mostly for commercials and short films. "It was a whole different kind of fulfillment than acting," McBride said in an interview on set in Senoia last week.

Acting was in her past, she figured. When a casting agency (Finncannon & Associates) asked her to audition in a Frank Darabont-produced film "The Mist," she resisted. Her boss Annette Stilwell, a huge Stephen King fan, convinced her to give it a try.

McBride was considered for a bigger role but she didn't want to take so much time away from her job. Instead, she found a smaller role more compelling, a two-minute scene in which she played a distraught mother. Her performance was so impactful,  Darabont offered her a role for his new show "The Walking Dead" in 2010.

She didn't even audition for Carol, which she figured was a short-term gig. She was only in three of season one's six episodes. "I figured my character was not going to live," she said.

McBride, who resembles Jamie Lee Curtis with her short hair and calm demeanor, bonded with the other Atlanta actors on the show, all of whom she had known when she was a casting director. IronE Singleton, who played T-Dog the first three seasons, remembers McBride booking him for a Rooms to Go ad back in the day.

"She was such a free spirit," Singleton said. "Very laid back, very cool. I pegged her as one of those individuals you'd run into at Woodstock."

And once he saw her acting, Singleton was wowed: "When she's in a role, you can look into her eyes and see her soul. She goes so deep down inside to get at Carol."

Carol and T-Dog. CREDIT: AMC

Rodney Ho

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Rodney Ho

Friends for life: Daryl and Carol. CREDIT: AMC

Rodney Ho

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Rodney Ho

During seasons two and three, Carol remained a secondary character. She lost her daughter Sophia to zombieland and bonded with one of the most popular characters Daryl Dixon (Norman Reedus). While they had chemistry, there has been no romance. (His character is rumored to be gay, for whatever that's worth.)

"Melissa is an open book," Reedus wrote in an email. "She feels everything she says and she means everything she does. That's why she's so good."

Last year, the writers gave Carol far more to do. She began secretly teaching the children how to use guns and knives. When a deadly but non-zombie-related virus began inflicting some of the survivors at the camp, she unilaterally killed two of them as a preemptive strike to prevent it from spreading.

"To Carol, there's no time for second guessing," McBride said. "She has to protect the people she loves."

When she confessed to leader Rick Grimes (Andrew Lincoln) about the murders while they were on a supply run, he exiled her, for fear this information would cause dissension back at camp.

By then, she was no longer a meek, abused wife but a strong, independent, pragmatic survivor who was able to live on her own. She ultimately reunited with young Lizzie and Mika. Lizzie, however, was so mentally imbalanced, she thought the zombies were still human and to prove it, she killed her sister.

Carol, in one of the most heart-wrenching scenes of season four, felt she had no choice but to murder Lizzie. To distract Lizzie before shooting her, she told the little girl with mock cheer, "Look at the flowers."

Later, she confessed to Tyrese (Chad Coleman) she had killed his girlfriend due to the earlier referenced virus, a fact he had not been aware of. She did so to clear her conscience and readied herself for his wrath. Surprisingly, Tyrese didn't attack her. Instead, during the incredibly tense yet poignant scene, he forgave her and they moved on.

"I was talking to someone today about how emotionally spent I often feel playing Carol," McBride said. "That scene was the most emotionally spent I have ever felt as an actress."

Without revealing anything spoilers, it's fair to say Carol remains a crucial cog in this Sunday's return of "The Walking Dead."

McBride hopes to stay on the show as long as the producers want Carol alive. "I love this character," she said. "She and the others are all living so immediately, so presently. There's nothing to look forward to. They have to deal with the here and now. It's a profound thing."

Singleton said Carol is an inspiration for many women in abused relationships. "Women have been empowered to take control of their lives because Carol showed them it can be done," he said.

TV preview

"The Walking Dead," 9 p.m. Sundays, AMC