From having the bounty and wanted notice against him lifted by the Ministry of Magic for lack of concrete evidence that he had murdered Dumbledore, to being appointed Headmaster of Hogwarts by the Board of Governors, Snape had remained remarkably indifferent throughout, as though it were all perfectly natural.
When he returned to Hogwarts, he ignored Hagrid's murderous glare, passed through the castle's oak doors, and headed straight for the Headmaster's office. During that short walk, Snape could feel the hateful stares of his former colleagues. Though they had all been careful to conceal the anger and hatred in their hearts, Snape knew they did not welcome him. They even wanted to kill him to avenge Dumbledore.
Yet, absurdly enough, he had merely done as Dumbledore instructed.
"As you wished, I have returned and become the most unwelcome man here!"
After entering the Headmaster's office, Snape walked up to the portrait of the former headmaster and spoke in a faintly mocking tone.
"Hogwarts School has fallen completely into Voldemort's hands." The old man in the sleeping portrait opened his eyes, looked at his successor, and said calmly, "I hope you will honor your old oath and do everything in your power to protect Hogwarts' students."
"That will not be easy." Snape's lips trembled as he said softly, "The Dark Lord demands that I expel all Muggle-born students. You know I do not have much power to choose."
After a brief silence, Dumbledore smiled. "That is only to be expected, is it not? Just like Salazar Slytherin, they are prejudiced against Muggle Wizards and want to drive them out of Hogwarts."
"The situation is even worse than you imagined."
Snape could not understand Dumbledore's composure. He pulled out a newspaper from several days ago from his robe pocket. "Perhaps you are