During the long period from 1348 to 1722 the plague raged with irregular intervals across Europe, and one of the last big epidemics of plague devastated all countries facing the Baltic Sea in the years from 1709 to 1713. This is the first time a serious epidemic in Early Modern Europe in such a big region is analysed in depth. The result is that the plague from this epidemic looks very similar to present day plague caused by the bacterium Yersinia Pestis. It spread from sick and dead rats by infected fleas to human beings. The only major difference being that the disease in the 18th century seems to have been infectious from man to man to a much higher degree than today.