Now, I know what you're thinking: "Dancing? Could be fun!" And, well, under normal circumstances and for certain people, it is fun. But imagine, if you will, an historical event where hundreds, even thousands, of people were seized by an uncontrollable urge… to dance. And I don't mean a casual waltz. We’re talking hours, even days of relentless, frenzied movement. Exhaustion, dehydration, heart attacks… all leading to some truly grim results. This, my friends, is the Dancing Plague, also sometimes referred to as St. John's Dance, and it's one of the most peculiar episodes in medical and social history.