More fanciful theories abound, too. Some historians suggest the legend reflects a 13th Century children’s crusade, part of the wave of medieval crusades aimed at winning back the Holy Land. And some argue the youth were lost to the Black Plague, though the dates don’t match up.

More intriguing is a theory that points to the medieval phenomenon of “dancing mania”, driven by a succession of pandemics and natural disasters. Known as St Vitus’ Dance, the dancing plague is documented surfacing in continental Europe as early as the 11th Century. A form of mass hysteria, the dance could spread from individuals to large groups, all driven by an unshakeable compulsion to dance feverishly, sometimes for weeks, often leaping and singing and sometimes hallucinating to the point of exhaustion and occasionally death, like a top that can’t stop spinning.

And, in fact, one 13th Century outbreak – a literal form of dance fever – occurred south of Hamelin, in the town of Erfurt, where a group of youths were documented as wildly gyrating as they travelled out of town, ending up 20km away in a neighbouring town. Some of the children, one chronicle suggests, expired shortly thereafter, having flat-out danced themselves to death, and those who survived were left with chronic tremors. Perhaps, some theorise, Hamelin witnessed a similar plague, dancing to the figurative tune of the Piper.

But all these theories neglect one specific key to the Hamelin mystery. “They don’t explain the very particular date cited for the loss of the children, and the local sense of trauma,” Reimer noted. “Did something happen that officials had been covering up? Something so traumatic that it was transmitted orally for so long in the town’s collective memory, over decades and even centuries?”