Date: August 21, 1321 (August 21, 1321)
The summer of 1321 was plagued with rumors that Jews had entered into a conspiracy with lepers (some versions also included Muslims) to poison the wells of Europe, resulting in mass hysteria and mob violence.
King Philip V was eventually able to quell the movement, but it resurfaced twenty years later in a much more potent form as the Black Death swept through Europe.