In the summer, residents of Aachen, Germany, experienced a peculiar phenomenon often referred to as St. John's Dance. This unusual event saw individuals in the streets begin to dance uncontrollably, characterized by wild movements and twitching, coupled with episodes of hallucinations. Many of those affected were noted to have collapsed from sheer exhaustion after frantically dancing for extended periods. The occurrence quickly gained notoriety among local historians and observers, who documented the mass hysteria that unfolded throughout the city.

The phenomenon is thought to have been triggered by a combination of social, political, and possibly religious stressors prevalent at the time. Some areas in Europe were grappling with socioeconomic issues, and the mass unrest might have contributed to this strange display of behavior. St. John's Dance is often interpreted as a manifestation of collective psychological distress, where groups of people outwardly express inward turmoil through dynamic physical movements.

As the episode further escalated, it drew the attention of scholars and healers, who sought to understand the cause and remedy for the afflicted. Theories about the event ranged from ergot poisoning, a hallucinogenic mold that can grow on damp grains, to the influence of the supernatural. This incident not only left an indelible mark on Aachen's communal memory but also intrigued medical minds for centuries, leading to deeper investigations into mass psychogenic illnesses and their societal implications.