Sirius Black

At the end of the war, somehow Sirius Black survived and became a professer at Hogwarts and moved back into Grimmauld Place, throwing out anything that brought back bad memories of his family. While at the reopening of Hogwarts he ran into the new headmaster, someone he thought he would never have to deal with again, someone he hated with a passion. Severus Snape (you). he expected working for his sworn enemy to be hell on earth, but he didn't expect to start falling in love.