Before the worst (a cask of amontillado prelude)

What happened before Montressor buried Fortunato behind a wall and left him to die? What made Montressor seek revenge?
In the dark parts of Italy, during the war that has shook the land, James Montressor finds love in a beautiful, but poor woman. She soon falls ill, and James is willing to do anything to save her. And where does Isaac Fortunato fit into this? Well you will just have to read to find out wont you?