Why So Awry?

Severus Snape had a life before teaching at Hogwarts. Though nobody is left to remember but a few, Severus had a best friend. His only friend. Robin Wilson, his companion. They were inseperable. He always told her that she was too nice to be a Slytherin. She always told him that she was his guardian angel. It seemed like a joke then, but maybe she was right. So what led Severus to join the deatheaters? What caused things to go so wrong?

Part 1 - 5th year at Hogwarts
Part 2 - 6th year at Hogwarts
Part 3 - 7th year at Hogwarts
Part 4 - 3 years later

Disclaimer: You know that I don't own J.K Rowling's characters or any of the original plot, no matter how many times I wish upon a star that I did. My dreams have not come true and the original ideas and concepts of Harry Potter still belong to her. Not me. So don't sue.