Dan Snow, Raksha Dave and John Sergeant retrace the final hundred days of Tutankhamun's life and the scientific investigation into his death. Modern forensic and genetic techniques applied to the mummified body of the nineteen-year-old pharaoh reveal deformities and health problems now linked to the fact that his parents were siblings, a common practice among Egyptian royalty meant to preserve bloodlines but one that left its mark on his skeleton. The team examines CT scans, DNA evidence, and artifacts from the tomb to reconstruct what killed him, weighing chariot accident, malaria, and inherited illness against each other. Interviews with palaeontologists and Egyptologists sit alongside footage from Luxor and the Valley of the Kings, tracing how incest within the royal family shaped not just Tutankhamun's body but the fragile end of his dynasty. The episode treats the boy king less as legend and more as a case study in what royal genetics can cost a family that rules by blood alone.