One day a cryptic anonymous message appeared online seeking highly intelligent individuals, kicking off the most elaborate digital scavenger hunt the world has ever seen. Between 2012 and 2014, an unknown entity called Cicada 3301 ran a multi-year puzzle demanding mastery of cryptography, ancient languages, and obscure literature just to get past the front door.

This episode plunges down the rabbit hole of Cicada 3301, from hidden messages buried in image pixels to QR codes taped to lampposts across five continents. We explore who might have built it, what the prize actually was, and why a decade later the runic Liber Primus remains largely unsolved.

• How least significant bit steganography hid entire text files inside a black-and-white cicada image, extracted with tools like Outguess
• Clues spanned William Blake, the Welsh ...