"My ex-husband phoned me, and when I first heard him say the words, that she was missing, I screamed ... It's horrible. It is indescribable. You don't know where your child is. You don't know if they're being hurt. You don't know if they're cold or hungry, or being abused," said Mullenberg's mother, Monica Lukasavige.
Unlike most victims' parents, though, Mullenberg's parents knew who had taken their daughter. On the day she was abducted, Mullenberg had taken a trip with her creative writing "mentor," Steven Oliver, who had been a teacher's aide in Mullenberg's school.
The father of one of her classmates, Oliver ran a writing club for students and told Mullenberg that a publisher was interested in a short story she had written.
On Sept. 16, 1995, she agreed to go with Oliver in his car to see the publisher. Mullenberg dozed off in the car and when she awoke, both her feet and hands were bound.
"I woke up, and ... my hands were tied behind my back," Mullenberg said. "And then he had ropes, like, over my legs and then under the seats. He told me he was taking me and that there was nothing that I could do."
After an eight-hour drive to Kansas City, Mullenberg and Oliver boarded a plane to Houston, where Mullenberg spent the majority of her three-and-a-half month captivity in a motel room.
Oliver registered them at the motel as father and daughter. He invented a story of family deaths, and changed Mullenberg's appearance.
"He cut my hair, dyed my hair ... And he would tell hotel workers that the reason why I would look depressed or sad was because my mom and twin brother [were] just killed in a car accident."
In captivity, Mullenberg's survival skills were tested like never before. Mullenberg was told that her name was Cindy Johnson and that she was to call Oliver "Dad."
"He threatened me all the time with, 'I'm going to kill your parents' and 'I'm going to kill your siblings if you ever say anything,'" she said.
Oliver got a job as the motel's painter and kept Mullenberg in a small room in an abandoned wing of the motel. Each day began with a "perimeter check." Oliver would scour the parking lot for Midwestern license plates, and when he was satisfied that no threat seemed imminent, he locked Mullenberg in the room and went to work.
Mullenberg says that physical, sexual and mental abuse were common.
"Almost every day, I was either raped or I was hit. If for some reason I didn't complete a sexual act that he wanted done a certain way, I would spend the entire day chained or tied to the bed," she said.
The telephone in the room was disconnected, and the 13-year-old had no way to escape and no one close enough to hear her screams.
Within weeks, Oliver had convinced Mullenberg that her parents didn't want to get her back, and didn't love her.
Mullenberg says she became so completely disconnected from reality that she remembered very little from her past.
"After ... probably a month ... I couldn't tell you my name," she said. "It didn't pay not to go along with what he wanted [me] to do or to say, because, you know, instead of getting hit once, it would mean getting hit 20 times. Instead of ... the back of his hand, it would be a pot or a chair or a broom. It was not worth it [to resist]."
Lost in a nightmare, she was ultimately rescued by an everyday hero: the motel's restaurant manager, who wishes to remain anonymous.