Victim of Golden State Killer survived because of 'obsession'

One of the youngest victims of the Golden State Killer had a "total obsession" with the serial rapist, and believes that may have saved her life.

Margaret Wardlow tells ABC's "20/20" in an interview that aired Friday night that she read all she could about his crimes before he showed up in her bedroom at her Sacramento home early on Nov. 10, 1977. She was 13 years old.

"I don't think I was the only person that was curious as to what was making this guy tick," she told ABC News. "And it was very clear that during the attacks he was using this fear that he was controlling people with, you know, by making them very much afraid of what he was saying to them and what he was doing to them."

Wardlow said she initially believed it was a neighbor's stupid joke when the Golden State Killer, believed to be Joseph DeAngelo, showed up in her room at 2 a.m. wearing a mask and gloves.

However, the intruder told her in a "harsh whisper" that "this isn't a joke," according to ABC News.

"And I knew at that moment, this is not my neighbor, Bill," she told the news magazine. "This is the 'East Area Rapist' most likely. And he's in my home."

Photos from the case:

Both Margaret and her mother, who was in a different room, were tied up and blindfolded. Already familiar with the East Area Rapist, as he was called then, she felt like she "had the advantage."

"A little voice inside of me said, you know, 'You get out of a lot of stuff, Margaret. But you're not gonna get out of this one. And just you need to understand that this is what's gonna happen to you. You're gonna get raped. But you're gonna be OK. And he's not gonna hurt me,'" she told ABC News.

She adds: "How many rape victims in this sort of situation with an unknown attacker have a dossier written about their attacker?"

Margaret said she survived the attack because she refused to show "fear."

"He wasn't getting what he wanted," she told ABC News. "He wanted fear. He wanted to see fear in me."

The 72-year-old DeAngelo, believed to have killed 12 people and raped at least 50 women, was arrested last month, more than 40 years after the attack on Wardlow.

"I was elated," Wardlow told ABC News. "I could not believe it. It was ... the most beautiful, beautiful phone call I've ever had. I mean, I was just so excited."