Transcript for Disgraced former teacher faces kidnapping victim in court
He can say all day long the devil made him do it, but he is the devil. Reporter: It has been a long journey for Elizabeth Tamas to come to grips with what a teacher did to her. But yesterday in a courtroom, the latest chapter closed as he pled guilty to taking a minor across state lines for sex in a case that gripped the country. New tonight, 15-year-old Elizabeth Thomas. Reporter: It all started in the spring of 2017 in the small town of kulleoka, Tennessee. Tad Cummins is a popular teacher at the high school. Everyone liked him. He was everyone's friend, mentor, helped so many people through some things. Reporter: Then 15-year-old Elizabeth Thomas is just making the transition from home school to public school. She says Cummins at the time 50 and married with two daughters, takes her under his wing. He gave me a bible. It was just something from him. Reporter: That kindness, even extending outside the classroom. Taking Elizabeth to church on Sundays with his wife. Did you ever think anything of their interactions together? It was like a father-daughter relationship, the way I saw it, too. Is the way he would explain it. I caught her with our daughter sometimes. Reporter: Elizabeth's family attorney thinks he recognized she was a vulnerable target. He was specifically grooming this child for a very specific purpose, and that was a relationship. He chose a girl who was having issues because she came to him for counseling. Reporter: Cummins posting you're all my heart talks about. It was love at first sight, at last sight. Then there's Elizabeth's response. I look forward to going to school just to see you, I love you. Most of them from him would be sexual texts. Reporter: Then alone with Elizabeth in his classroom she says Cummins goes a step further. He said you'd look nice naked. A student reported seeing Elizabeth Thomas kissing Cummins inside his classroom. The student was disturbed by what she saw and immediately reported it to school officials. Reporter: The school investigates but Elizabeth denies everything. Children spend the majority of their day with their teachers in school. And so that power dynamic almost takes the place of the parent-child relationship. What child is going to speak out against the person that is in control of the majority of their lives? Reporter: The school suspends Cummins for inappropriate conduct with Elizabeth. Over the following weeks, Cummins continues reaching out to her over social media and hatches a plan to run off with her, telling her he'll hurt himself or someone else if she doesn't go along. So on the morning of March 13th, she leaves her home, seen here in this surveillance video obtained by ABC news. At 8:32 A.M., Cummins stops at a local gas station and fills up his tank and then picks Elizabeth up at a shoney's restaurant. He had a gun in the middle console, and I knew I wasn't getting out of the car. Reporter: And you knew then? I wasn't getting out of this. Reporter: By that evening, Elizabeth's father reports her missing. A man hunt for Cummins is immediately under way. The tbi issued an amber alert. I miss you, please, please come home. Reporter: Cummins' wife Jill, making an emotional plea for his return. Tad, this is not you. This is not who you are. We can help you get through this. Reporter: For 38 days, he drags Elizabeth on a cross-country trek through nine states, evading authorities. He made me throw my phone off a bridge and his phone as well, that way the police couldn't track us. Then he disconnected the gps a screwdriver in the glove compartment and broke off the front and unhooked the radio. It was like a kidnapping. I had to stay in the car with him at all times. Reporter: She says Cummins made her sleep without clothes on, hiding them from her and watching her every move. He said we were going to get married and I was going to live with him until I died. Reporter: As days turn into weeks, Cummins decided to take his victim south of the border by kayak. So he got a kayak and wanted to kayak all the way to Panama. Reporter: When did he decide we need to turn around? When one wave nearly killed us and took us over. Once we got out of it I was so happy. Reporter: Cummins then sets his sights on a northern part of California. They were offered shelter from griffin Barry. Cummins makes up a story about why he came to California. Yeah, he said I had a house fire, lost his job. They were just trying to start a new life. I was like, I'll help you out. I put them in the cabin. Reporter: But Barry senses something strange were the girl. I was like, that girl won't talk to me, really, or anything. Reporter: Barry's neighbor shows him Elizabeth's amber alert. I saw a photo of the guy, and I was like, that's definitely him. Reporter: Then what did you guys decide to do? We went and called the police. Reporter: Authorities rushed to the area and an S.W.A.T. Team surrounds the cabin where they are staying. The day the police show up. That was the best day of my life. Reporter: Less than 24 hours later, Elizabeth flies home to Tennessee, starting a journey of healing and understanding. I know he's a bad man, and I blame myself a lot, but now I know he's at fault. He himself made him do it. It is extremely common for victims, especially child victims of sexual assault, sexual predation, to blame themselves. I think it is one of the reasons why sexual assault is the most under-reported crime in our country. Because people, not only believe that they will not be believed, they blame themselves for it even occurring in the first place. Reporter: Elizabeth facing Cummins in court yesterday with a powerful message for her captor, saying in part, you preyed upon a vulnerable girl and robbed her childhood. For the last two years, I've been picking myself up, piece by piece and proving to myself that I am much, much stronger than you convinced me I was. Your choices destroyed not just my family but also yours. Elizabeth asked the judge to sentence Cummins to 38 years in prison, one for every day he kept her. Ultimately, the judge decided on 20 years. He will have to spend the majority of the 20 years in prison. He will have to register as a sex offender for the rest of his life, and he will never be able to be alone with a child again. Reporter: Elizabeth is focussing on what she can, moving on. What are your dreams for your life? To have a family and protect them. Make them have a better life and a stronger person than I was. And I'm not afraid. Our thanks to Eva pilgrim.
This transcript has been automatically generated and may not be 100% accurate.