"Oprah and Lance Armstrong: The Worldwide Exclusive" continues January 18 on OWN and Oprah.com. In this clip, Armstrong talks to Oprah about the moment he told his 13-year-old son, Luke, the truth.
"When this all really started," Armstrong says, "I saw my son defending me and saying, 'That's not true. What you're saying about my dad is not true....' That's when I knew I had to tell him. And he'd never asked me. He'd never said, 'Dad, is this true?' He trusted me."
Part two of Oprah's interview with Lance Armstrong aired Friday, Jan. 18, starting at 9 p.m. ET on OWN. The interview was simultaneously streamed LIVE worldwide on Oprah.com.