In September 1987, scrap scavengers in Goiania, Brazil pried open a punctured metal capsule and found a mesmerizing deep blue glow inside. They rubbed the powder on their skin like carnival makeup and let their children play with it. The glow was cesium-137, one of the most dangerous substances on Earth.

This episode traces how a scavenger hunt for scrap metal became an INES Level 5 radiological disaster, one of the worst in history. It's a chilling study of institutional negligence colliding with innocent human curiosity, and how a deadly source ended up in civilian hands because a single security guard didn't show up for work.

• How an abandoned radiotherapy clinic left a teletherapy unit behind, trapped by a lawsuit despite repeated warnings to authorities
• Why the water-soluble cesium salt spread like glitter through hom ...