It's more than 50 years since Marilyn Monroe died, and still the fascination with the blonde bombshell continues. The latest personification is the Lifetime four-hour movie, "The Secret Life of Marilyn Monroe," in which Kelli Garner follows in the footsteps of Catherine Hicks, Poppy Montgomery, Mira Sorvino and, most famously, Michelle Williams to capture the essence of Monroe.

Based on the eponymous book by J. Randy Taraborrelli, "The Secret Life of Marilyn Monroe" looks at the woman who transitioned from being plain Norma Jean Baker to the world's most famous sex goddess through the prism of  mental illness. Monroe's mother Gladys Mortenson, aptly played by Susan Sarandon, was in and out of mental hospitals, and this project implies that Monroe inherited her mother's illness.

"For me, I approached this as historical fiction," Garner tells FOX411, "but her mother was definitely diagnosed schizophrenic. So while I think it was brave to talk about mental health, I don't know for certain."

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"The Secret Life of Marilyn Monroe" begins with Monroe's peripatetic early life as she is removed from her mother's care and ends up in the foster care system, to her early marriage, her struggles to become a movie star, and ends with her death at 36 of a probable drug overdose.

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Garner admits to not being familiar with Monroe's life story, and to only having seen two of her movies --  "Some Like it Hot" and "The Seven Year Itch," so she began her study by viewing the rest of Monroe's films, reading the biography, and looking at interviews and photos.

"I was really uneducated about her as an actress," Garner says. "After I saw the script, which I loved, and after I saw 'The Misfits' … I think 'The Misfits' was my way into finding her. Then I just started trying to trust myself and my instincts."

To land the role, Garner, who previously starred in the 1960s-set series "Pan Am," donned a red, polka dot dress, and spent three hours utilizing the vintage makeup and hair tricks she had learned on her previous job, transforming herself into a version of Monroe. 

But once she was cast, the real transformation began. She says, "I remember there was a fight as to how many wigs we needed to take her from Norma Jean to her death. There were all these discussions about hair and length and what everyone's interpretation was of what the ultimate Marilyn looked like. I ended up wearing seven wigs within the mini-series."

And even with a professional team creating the look, Garner had her reservations. "I knew everyone was talented, but I felt so relieved that I didn't look silly, so that I could do the best job without being self-conscious. I was, 'I am in this iconic hair and makeup getup, am I going to feel great?' They did a great job."

Garner also said it was great working with the Oscar-winning Sarandon.

"She's so smart as a woman," she says. "It was great just getting to spend time with her and see how she interacts on set and the choices she makes. To see her throw things out there … and Emily Watson [who plays Grace McKee, a close friend of Gladys,' who initially cared for Norma Jean when her mother was committed] was so great, too."

And despite her immersion in the culture of Marilyn Monroe, Garner still hesitates to venture an opinion on whether her death was a suicide, a tragic accident, or the more shocking but unsubstantiated idea that it was murder.

"I have heard so many different things," she says. "I don't want to think that she killed herself. That's a hard one for me. That one makes me sad."

"The Secret Life of Marilyn Monroe" airs Saturday, May 30 and Sunday, May 31 on Lifetime.

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