"I stupidly believed Snape's memories. I should have known that was part of Dumbledore's master plan. He spelled his Pensieve to corrupt Snape's memories when they interacted, as though he expected that I'd get to see them in some fashion. Dunno if he knew Snape would have to be killed for it. Not that he would have cared. He was a sly old bastard as it turns out.