In the third installment of the Harry Potter series, The Prisoner of Azkaban, Harry and Oliver Wood were on edge the day before their Quidditch match. Adding to their stress was the buzz around the castle regarding Sirius Black's escape and subsequent presence within Hogwarts. As one of his favorite teachers, Remus Lupin, was absent and Arthur Weasley had warned him not to go looking for Black, it was not a particularly enjoyable time for Harry. Professor Severus Snape had taken over for Lupin as the Defense Against the Dark Arts teacher and in chapter 9, "Grim Defeat," Harry overheard a conversation between Snape and Albus Dumbledore. Snape expressed his doubts about Lupin's appointment and suggested that Black could not have entered the school without inside help. Despite Dumbledore's dismissal of the theory, Snape maintained his lack of trust in Lupin.
Snape Fills In For Remus Lupin
Upon arriving late to his Defense Against the Dark Arts lecture, Harry finds Snape at the teacher's desk. As punishment for his tardiness, Snape deducts ten points from Gryffindor and instructs Harry to take his seat. Harry inquires about Professor Lupin's absence but Snape only responds with a twisted smile. He proceeds with the lecture, criticizing Lupin for his lack of organization and failure to leave any record of covered topics. Hermione interjects, defending Lupin's teachings and listing the topics they have already covered. Snape becomes agitated and dismisses Hermione's input, stating his belief that the students should be challenged further. He then abruptly switches the topic to werewolves and scolds the class for their lack of knowledge. Snape's behavior hints at a hidden agenda, leaving the students to wonder what is happening under their noses.
Professor Snape Set The Essay
Snape's laser focus on Werewolves hints at an underlying motive, as evidenced by his demand that third-year students recognize and kill them. In both the book and movie versions of Harry Potter and the Prisoner of Azkaban, he assigns an essay on the topic and insists on its completion by Monday morning. It becomes clear why Snape is so fixated on the subject when Hermione reveals that Lupin is a Werewolf and Snape suspected him of aiding Sirius Black. In setting the essay, Snape had hoped that a student would recognize Lupin's condition and expose him. Hermione's completion of the assignment accomplishes Snape's intended goal.