Investigation documentaries delve into mysterious phenomena, tragic incidents, and past conflicts. These documentaries seek answers to some of the most difficult questions and report on investigations that often reveal shocking truths. Discover huge mystical craters in Russia, or learn about opium production in Afghanistan. Investigation documentaries show how the black market in organs thrives in Nepal and dig into the alleged collaboration between the Turkish government and ISIS militants. Watch an RTD investigation into sleeping sickness in Kazakhstan, or searching for the truth behind the MH17 crash.