Severus wasn't sure how long he sat, absorbed in the silence. He was worried about Hermione.
For once in his life he had let himself be guided by his heart instead of his head, and now he was in this unbearable situation. He was not even sure when his heart had taken over.
After he had to perform the Killing Curse on the only person who had completely trusted him, his first obligation had been to protect Draco. He was not sure why Dumbledore insisted upon this, but he suspected that Draco's actions had reminded Dumbledore of another young Slytherin.