Rin and Yukio Okumura are getting ready to return to Hogwarts for their third year when they hear that mass murderer Sirius Black escaped Azkaban prison. Everyone thinks he's after Harry Potter. While everyone at school is keeping their eyes peeled for the escaped convict, the Okumura twins can't help but feel like they heard Black's name from somewhere.

Rin and Yukio return to Hogwarts for their second year, but something evil is lurking within the school. Students are being Petrified left and right and all evidence points to Harry Potter. What is attacking the students? Is it a monster? A demon? Or something else?