The city lord issued a decree to eliminate the rat problem: one rat tail in exchange for a silver coin.

What was originally a kind act quickly turned the entire city into a dead city.
Under heavy rewards, the whole city fell into madness.
The citizens, day and night, dug into the sewers with shovels and torches to catch rats.
A month later, the square was piled high with severed rat tails, and silver coins were distributed like flowing water, visibly reducing the rat population in the city.
Half a year later, the treasury was nearly empty, but the number of rat tails brought in for silver coins had doubled.
The city lord grew suspicious and sent people to investigate secretly.
They saw an absurd scene: those catching rats had built huge underground farms.
They fed the rats with precious grain, making them fat and healthy, then, like cutting chives, they repeatedly cut off tails to exchange for silver coins.
No one cared about the city's survival; everyone was madly exploiting loopholes in the rules.
The city lord was furious and immediately tore up the decree, declaring rat tails worthless.
The citizens’ dreams of wealth were instantly shattered.
They angrily kicked over the iron cages and threw thousands of hungry live rats back into the city.
In one night, the black tide of rats completely engulfed the streets.