The Black Death had such a devastating effect on society that it precipitated the crumbling of the old feudal European medieval order and ushered in the modern world. But what actually caused the Black Death – and how many people died – is still a mystery. Contemporary accounts tell how the Black Death killed rich and poor, old and young alike; how victims suffered from painful boils, bleeding from the ears and black spots. The world has seen nothing like it, before or since. Now, a new investigation of recently unearthed skeletons from a long-lost plague cemetery discovered beneath the streets of London could settle the hottest debate in history once and for all. Uncovering the crucial clues hidden in the bones of the victims, this fascinating film reveals exactly why this was the biggest killer in history; and what it can teach us about pandemics to come.