Yesterday on “The Daily,” we heard about the government’s failure to crack down on the explosive growth of child sexual abuse imagery online. In the second half of this series, we look at the role of the nation’s biggest tech companies, and why — despite pleas from victims — the illicit images remain online. Guest: Michael H. Keller, an investigative reporter at the The New York Times, and Gabriel J.X. Dance, an investigations editor for The Times, spoke with the mother and stepfather of a teenager who was sexually abused as a child. For more information on today’s episode, visit nytimes.com/thedaily.