Imagine stepping out onto the streets of your town to find your neighbors in a strange frenzy, dancing uncontrollably to an invisible tune. No music, no celebrations—just relentless, exhausting motion. It might sound like the plot of a surreal film, but this was the stark reality in Strasbourg, Alsace, in the summer of 1518. The ordeal began innocently enough when Frau Troffea started dancing in the streets. There was no explanation, no apparent cause, and certainly no warning. What...