From the front line of the Camp Fire, the deadliest wildfire in California history, NOVA tells the stories of residents who had to flee for their lives during the 2018 fire season. Scientists racing to understand what's behind the rise of record-breaking megafires across the American West take to the forest, and even a fire lab, in search of answers. They investigate how forestry practices, climate change, and the physics of fire itself play a role in the dramatic increase in wildfires in recent decades.

Forty years ago, hundreds of skeletons were unearthed in a mass grave in an English village. Bioarchaeologist Cat Jarman believes these bones are the last remains of the "Great Heathen Army," a legendary Viking fighting force that invaded England in the ninth century and has long been lost to history. Armed with the latest scientific methods, Cat's team uncovers extraordinary human stories from the front line, including evidence of women fighters and a lost warrior reunited with his son in death.