In July 1518, in the free imperial city of Strasbourg in the Holy Roman Empire, a woman recorded as Frau Troffea stepped into a street and began to dance, and could not stop. Within a week some thirty others had joined her; over the following weeks the compulsion drew in as many as 400 townspeople, who danced for days on end, many past the point of exhaustion. Contemporary and near-contemporary chroniclers reported that some collapsed and that a number died from the strain — figures the documents do not let us pin down with confidence. The episode swelled through July and August and then faded of its own accord by early September, ending about as mysteriously as it had begun.
The outcome is not a mystery, even if the cause is debated. No supernatural curse seized Strasbourg, and the modern consensus, argued most fully by the historian John Waller, is that the dancing plague was an episode of mass psychogenic illness — a physical contagion of behavior with a psychological origin, spreading by suggestion through a population already pushed to the edge. The city in 1518 had endured successive famines, harvest failures, and disease; into that misery ran a regional belief that Saint Vitus could afflict sinners with an uncontrollable dance. The dancers were not faking and were not, in any ordinary sense, choosing; under extreme stress and shared expectation, their distress took the culturally available shape of compulsive dancing, and the sight of one dancer made the next more likely.
This dossier treats the Dancing Plague as a closed case with a documented ending — not a ghoulish curiosity but an early, unusually well-attested instance of how a community under strain can fall into a shared, involuntary affliction. The mechanism is the point. The authorities, reasoning from the medicine of their day, made the outbreak worse before they made it better: judging the dancers victims of “hot blood” that had to be danced out, they supplied halls, musicians, and professional dancers to keep them moving. Only when that failed, and the afflicted were marched to a shrine to be cured by ritual, did the contagion subside — by which time the panic had run its natural course.
In the first two weeks of September 1944, the small manufacturing city of Mattoon, Illinois, believed it was being stalked by a “mad gasser” — a prowler who crept to people’s windows after dark and sprayed a sweet-smelling, paralyzing gas into their bedrooms. Beginning with a report on the night of 31 August and exploding after the local Daily Journal-Gazette ran the story of Aline Kearney as a “first victim” on 2 September, roughly two to three dozen residents told police they had been gassed, reporting a strange odor followed by nausea, dryness of the mouth, and temporary weakness or paralysis of the legs. Armed patrols and state investigators combed the city. They found no gas, no chemical, and no gasser.
The outcome was settled within weeks and has not been seriously disputed since. No attacker was ever identified, arrested, or shown to exist; no one suffered any lasting injury; and no device or substance capable of producing the reported attacks was ever located. By 12 and 13 September the police chief, C. Eugene Cole, and the city’s commissioner of public health were publicly attributing the episode to imagination and overwrought nerves, and the supposed gassings, which had peaked sharply, stopped almost as abruptly as they began. The case entered the scientific literature the following year as a model of collective delusion.
This dossier treats the “gasser” as what the evidence shows: not a criminal but a panic. In 1945 the social psychologist Donald M. Johnson published “The ‘Phantom Anesthetist’ of Mattoon: A Field Study of Mass Hysteria” in the Journal of Abnormal and Social Psychology, tracing how an anxious wartime town, primed by a sensational newspaper, converted ordinary smells and ordinary ailments into a coordinated assault by an invisible enemy. The interest is in the mechanism. Sincere, frightened people genuinely felt their symptoms; the symptoms were real and the attacker was not, and a single suggestive headline supplied the script that an entire community then performed.
For roughly two weeks in November 1938, the West Yorkshire mill town of Halifax believed a razor-wielding maniac was loose in its streets, slashing women and the occasional man under cover of darkness. The scare began on 16 November, when two local women, Mary Gledhill and Gertrude Watts, said they had been attacked by a mysterious man with a mallet and “bright buckles” on his shoes; further reports of a phantom with a knife or razor followed, the press christened him the “Halifax Slasher,” and by the last week of the month the town was in the grip of panic. Vigilante mobs patrolled the streets, business all but stopped, and several innocent men, mistaken for the attacker, were beaten by frightened crowds.
The outcome is documented and unambiguous: there was no slasher. On the evening of 29 November, one of the supposed victims, Percy Waddington, admitted that he had inflicted his own wounds. Others quickly confessed the same, and Scotland Yard, which had been called in to assist the overwhelmed local police, concluded that the attacks had been either self-inflicted or imagined. Of the reported victims, all but a few acknowledged that no assailant existed. The scare collapsed within days of the first confession; the local press soon declared it over.
This dossier treats the Halifax Slasher as what the evidence established within a fortnight: not a criminal but a contagion. The wounds were real and so was the terror, but the attacker was a fiction assembled out of newspaper reports, nervous suggestion, and the strange pull of a town-wide drama in which to be a victim was to be, briefly, the center of attention. Five people were ultimately charged with public mischief and four were sent to prison. The interest lies in the mechanism: how an entire town came to hunt, and to fear, a man who had never existed, and how the same newspapers that built him helped take him apart.
Between 1788 and 1790, London was gripped by fear of a phantom assailant the newspapers christened the “Monster”: a man said to approach well-dressed women in the street, insult them, and slash their clothing and their bodies — most often the thighs and buttocks — with a blade before vanishing. Over fifty women reported such attacks. In the spring of 1790 the panic reached its height, and on 13 June a 23-year-old Welsh artificial-flower maker named Rhynwick Williams was arrested after one victim, Anne Porter, identified him in a London park. He was tried at the Old Bailey, convicted, and imprisoned for six years. The reported attacks then largely ceased.
The verdict of history is more troubled than the verdict of the court. Williams was convicted on evidence that contemporaries and later historians have found seriously deficient. He had alibi witnesses for the attack on which the case against him was strongest — fellow workers who swore he had been making artificial flowers at the time. Descriptions of the Monster given by victims did not match him. Some women who had reported attacks and later saw him in court said he was not their assailant. A pamphlet by the writer Theophilus Swift argued his innocence at the time. Reports of further attacks persisted after his imprisonment, when he could not have committed them. The historians who have examined the case most closely regard Williams as a probable scapegoat — a real man punished to satisfy a frightened city — and that doubt must sit at the center of any honest account.
The episode is now read as a phantom-attacker panic: a genuine fear, fed by lurid press coverage and by a large cash reward, that almost certainly outran whatever real assaults may have occurred. The reward, posted by the merchant John Julius Angerstein, proved especially corrosive. The prospect of money produced a wave of accusations; men were dragged before magistrates, mobs harassed strangers, and some “victims” were later shown to have invented or exaggerated their injuries. Whether a single attacker ever existed remains uncertain. What is certain is that a city’s terror produced a conviction that the evidence did not support.
This dossier treats the London Monster as a closed episode with a sober and uncomfortable ending. The panic broke when a man was found to blame, not when the truth was established. The harm it left includes the women who were genuinely frightened, the strangers menaced by mobs, and — soberly — Rhynwick Williams, who served six years on proof that may not have been sound.