This is related to the plague that unfortunately cost millions of casualties in Europe during the Middle Ages... In Season of the Witch, Nic is reportedly trying to secure a girl accused of withcraft and of being responsible for the plague, no less (poor thing, she would have been busy beyond her means...)

Now, the plague was the most terrible threat of that era but nowadays it´s forgotten and we cannot have a real sense of the doom that awaited those unfortunate enough to be infected... But some reminders have arrived to our present time.

I was most impressed when I visited this place in Edinburgh. It was like travelling back in time to actually feel the terror and the pain. Please click on the link and read on (if you´re so inclined, that is):

http://en.wikipedia.org/wiki/Mary_King's_Close