Because Sirius had been spotted in Hogsmeade, the Ministry of Magic had dispatched a large number of Dementors to patrol the area, and they were creeping ever closer to Hogwarts. However, constrained by Dumbledore's demands and his formidable presence, they could only lurk along the outer boundaries.
Still, this cast a heavy cloud over the students' spirits, and Sirius was not one to stay safely put. Unable to contain his impatience when Harry played in a Quidditch match, he slipped out to watch, prompting the Dementors to defy orders and cross into Hogwarts territory in an attempt to capture him.
Though Sirius narrowly escaped, Harry, while chasing the Golden Snitch, was once again incapacitated by the Dementors. Panic and unease gripped the school once more, leaving Iblis with no choice but to take action as soon as possible.
Chapter 90