The second half of the documentary examines the cause of the disaster, and how the Soviet authorities quickly pointed the finger at operator error, intentionally concealing a flaw with the reactor design. Plus, a look at how the conflict between Ukraine and Russia risks unleashing further radiation by damaging the hastily built shelter entombing the wreckage.

Witnesses and survivors tell the story of the world's worst nuclear accident, and the subsequent attempt by the Soviet government to cover it up. On the night of the explosion, the 50,000 residents of nearby Pripyat knew nothing of the disaster, until 36 hours later when local officials ordered a total evacuation of the town.