In 1945, the codebreakers who cracked Enigma and Japan's Purple cipher were handed a small 15th-century book and told to read it. Every one of them failed. Today, AI, deep learning, and the world's top linguists are no closer than an alchemist in Prague was 400 years ago. Welcome to the world's most mysterious text.

This episode steps inside a 600-year-old escape room, examining every physical, historical, and mathematical clue in Yale's MS 408. From radiocarbon-dated calfskin and fantastical plants to the graveyard of failed decipherments, we explore whether the manuscript is an elaborate hoax, an unbreakable cipher, or something stranger, and why it has become the ultimate mirror for our need to find meaning in chaos.

• How carbon dating and multispectral imaging prove the parchment is genuinely from 1404 to 1438 and never forged ...