In one sense, the ending is found in the first chapter. David Pelzer begins his story with the chapter titled "The Rescue," and he describes how he finally escapes his mother's abuse. A nurse at school takes note of his shabby clothing and scarred stomach and brings in other adults at the school to investigate his condition. They make a phone call, and a police officer comes to school to investigate David's injuries. They bring David food, which he "gobbles down so fast [he] can hardly taste it," and then the officer leaves with David, telling him that he is finally "free." He convinces David that his mother is never going to be able to hurt him again. The chapters that follow this one are all flashbacks from that point, describing the abuse that leads to this moment. So in that way, the ending is the conclusion of all of the abuse that David endures for so long.
In another way, the ending is found in the Epilogue. As an adult, David describes what has happened since his childhood. He has become thankful for the people who had a positive impact on his life. He enlisted in the United States Air Force and learned a sense of pride and belonging that he had never known until that time.
But perhaps most significantly, he has become a father himself, and the ending is a tender scene of David looking down at his son Stephen, a tear rolling down the side of David's cheek as he savors the beauty of his life. His son tells David, "Love you, Dad," and David reminds Stephen that he loves him, too. His final words of the book are "I'm free," which echo the early promise of the police officer as he rescued David from his mother.