Disclaimer: I do not own Harry Potter (even though I should), nor do I own "On the Nature of Daylight" (it was composed by Max Richter), and I do not own "This Bitter Earth" (which is sung by Dinah Washington). The quotes that are taken directly from the books are italicized and nestled between quotation marks.
Knowledge
He knew the instant he saw her face. He'd known her for years and she was incapable of hiding all of her emotions from him. He saw the almost-smile pass over her lips and light up her eyes when Potter had cast Levicorpus on him. Of course, it would be Potter wouldn't it? The one person that engenders as much hate in me as Sirius Black and she – she had to go and become infatuated with him. That's what did it really, that brief look of happiness over his humiliation. That's what made him say it. "I don't need help from filthy little Mudbloods like her!" Oh Merlin, Lily!