On April 20, 1999, Eric Harris and Dylan Klebold walked into Columbine High School in Littleton, Colorado. Over the course of minutes, they would kill 12 students and a teacher and wound 24 others before taking their own lives. For the last 16 years, Sue Klebold, Dylan's mother, has lived with the indescribable grief and shame of that day. How could her child, the promising young man she had loved and raised, be responsible for such horror? And how, as his mother, had she not known something was wrong? Were there subtle signs she had missed? What, if anything, could she have done differently? Here, she chronicles, with unflinching honesty, her journey as a mother trying to come to terms with the incomprehensible, in the hope that the insights and understanding she has gained may help other families recognise when a child is in distress.