1810 England, the height of the Napoleonic wars. It was thought that humans walked the path of enlightenment leaving monsters and dark things behind. However, those monsters and night stalkers merely hide in the darkness, as a young maid, Bernadette, soon finds out.
The symbol that Angela is drawing on Jinny's forehead is a real alchemy symbol; in this case it is the symbol representing antimony. I'll tell you what antimony represents in alchemy and my interpretation of it's use later. I don't want you to jump to any conclusions in this case; I want you to remain mystified for now.