Mass hysteria devastated two English communities when phantom attackers—the Hammersmith Ghost and Halifax Slasher—terrorized the public, yet neither perpetrator truly existed. In 1803, a man was executed for shooting an innocent bricklayer mistaken for a supernatural specter; in 1938, thousands hunted an attacker who existed only in panicked imaginations, revealing how collective fear can override reason and create violence from nothing. Francis Smith shot and killed innocent Thomas Millwood in 1803 after mistaking his white work clothes for the Hammersmith Ghost, exposing how mass panic can lead ordinary people to commit lethal violence against neighbors.