"There it was, hanging in the sky above the school: the blazing green skull with a serpent tongue, the mark Death Eaters left behind whenever they had entered a building… wherever they had murdered…"
When Dumbledore arrives at Privet Drive...
"'You are sharing the Dark Lord's thoughts and emotions. The Headmaster thinks it inadvisable for this to continue. He wishes me to teach you how to close your mind to the Dark Lord.'"
Dark times have come to Hogwarts. After the Dementors' attack...