The beaked plague doctor is the ultimate symbol of the medieval Black Death, instantly recognizable from films, games, and Halloween festivals. But almost everything we picture about this figure is warped. The famous costume did not exist during the medieval plague, and the men behind the masks were rarely the mystical healers of legend.

This episode strips away the theater to reveal the messy origins of public health. The real plague doctors were 17th-century municipal workers, often untrained empirics who performed demographic accounting, recorded wills, and applied frogs to buboes, all while terrified of breathing in what they believed was disease-carrying bad air.

• How miasma theory shaped a costume that accidentally worked as effective protective equipment
• Why collapsing cities paid a premium for what amounted to data ...