In this replay episode: On a beautiful summer morning in 1908, a massive explosion hit Siberia. It downed 80 million trees and lit the night sky 3,000 miles away in Sweden. But to this day, no one knows what caused it.

The Backstory: The London Fog That Killed 12,000
10:19

The Backstory: Sibling Squabbles in Royal Families
09:59

The Backstory: Famous Cat Lovers
06:59