The Plague that will wipe out nearly half of Europe's population starts with something so small as a rat. These small vermin transmit the black death throughout Europe and parts of Africa.
The Plague wipes out nearly half of Europe's population causing the pay of the serfs to increase and the power of the lords decrease. However the increase of pay meant very little because of the increase of inflation of goods.
After the plague, the Peasants demanded that they have improved living conditions and be paid their just due for working the land. This was accomplished however it was all in vain as the prices of goods rose as a result of the increase of pay.