Severus Snape and the New Teacher

Severus Snape is going back to Hogwarts for another year of teaching Potions. Once again, he didn't get the Dark Arts job. But something is different about this new Defense Against the Dark Arts teacher. Snape is in for a rough year thanks to the new teacher, Professor Quinlynn. Harry Potter is now the least of his worries. Professor Quinlynn my OC, takes place during book 4