It wasn't me Sir

Sara had a crush on her teacher the moment he entered the class. He was charming, sweet and passionate about teaching his students. Although his methods of teaching were terrible but he tried hard to make sure they all passed the exams.
But then something bad happened to him and he lost interest in teaching. He suspected few of his students to be the cause of his grim behavior.
Sara was one of them. With the help of her classmate, she tried to convince her professor that she couldn't be the cause but her current condition made it difficult to convince him.
It wasn't her fault that he changed.
Or was it?
Meanwhile, illegal medical businesses and experiments were taking place in her hometown. The people weren't being told the ugly truth. Worse, none were aware of it, including her.