Once upon a time there was a town composed of two parallel streets. A dervish passed through one street and into the other, and as he reached the second one, the people there noticed that his eyes were streaming with tears.
"Someone has died in the other street!" someone cried, and soon all the children in the neighborhood had taken up the cry.
What had really happened was that the dervish had been peeling onions.
Within a short space of time the cry had reached the first street. The adults of both streets were so distressed and fearful, since each community was related to the other, that they dared not make complete inquiries as to the cause of the furor.
A wise man tried to reason with the people of both streets, asking why they did not question each other. Too confused to know what they meant, some said, "For all we know there is a deadly plague in the other street."
This rumor, also spread like wildfire, until each street's residents thought that the other was doomed.
When some measure of order was restored, it was only enough for the two communities to decide to emigrate to save themselves. So, from different sides of the town, both streets entirely evacuated their people.
Today, centuries later, the town is still deserted and not so far away are two villages. Each village has it's own tradition of how it began as a settlement from a doomed town, through a fortunate flight, in remote times, from a nameless evil.
Note: I read a similar story years ago, about a mad dog with rabies who bit a child, who bit someone else, who bit another, and so it went until everyone in the town died of rabies. Apparently, what really transpired was that a stray dog barked at a cow! I cannot recall the author. The story above was narrated by Sheikh Qalandar Shah. His shrine is in Lahore, Pakistan.