In a CBS News, "48 Hours Mystery" exclusive, a Missouri boy reveals his heartbreaking account of the four years he spent as prisoner of the deranged pervert who kidnapped him.

"There wasn't a day when I didn't think he was just gonna kill me. Sometimes I thought I was better off dead than just living through that," 17-year-old Shawn Hornbeck says of the four years he was held captive. "The thing that sticks out the most" he adds, "is that he said, 'You were in the wrong place at the wrong time.'"

Hornbeck was abducted as he was riding his bike near his home. He opens up about his ordeal for the first time and shares details of what happened when after four years, his kidnapper brought home another boy. "The days got slimmer cause it's a replacement. When you get a new car what do you do with the old one? You usually get rid of it, right?"

Threatened with death and the death of his family, Hornbeck made a deal with the devil and promised never to run away or call for help. He kept his promise until the FBI agents came knocking on the door and rescued him.

To view a clip of the interview, click here.

"48 Hours Mystery" airs tonight at 10 p.m. ET/PT on CBS.