Severus Snape had never met a Muggle worth trusting. There had been his father, a hard man at best, but he was rarely at best. Mostly, he was cruel, abusive, ignorant of the treasure he'd found in his wife, and eager to take advantage of her powers while dismissing her humanity. There had been Petunia Evans, terrified of what she didn't understand, then envious to the point of hatred. There had been the children and teachers at primary school, who had ignored or made fun of him for his awkward manners and unfortunate clothes. He was better off without them, beyond a shadow of a doubt, and a leader appeared to make that dream come true.
He had pledged allegiance. He was skillful and inventive and sly, and the leader singled him out from the many who had joined to be part of the "inner circle." And then came the conflict: not only would they eliminate Muggles, but Muggle-born witches and wizards. And this seemed an ugly decision to the pale boy with perpetually greasy hair, because who better understood the plight of magic-makers than those who had to interact with the non-magical? Who better understood their privileges and their burdens? And who, in their pursuit of understanding magic, could be more passionate, more relentless, than…Lily?
And here was her son, looking at him with her eyes, asking him questions that she, too, would have asked, had she been given the opportunity. They were fair questions, and he had answered them as honestly as he had dared. And then the time came for him to attack the boy's mind. He hadn't wanted to. Or rather, he'd have never chosen to. He wanted the boy to repulse him at once, to protect himself, to be remarkably, uncannily adept at Occlumency. But such was not the case. The boy was Lily's. There was fire in his heart that would not be cooled, there was a total disregard for counting the cost of one's selfless actions. He was vulnerable.
There was no doubt in Snape's mind that this boy would be Lily all over again; he would lose her all over again in her son, in those almond-shaped, emerald eyes that he had spent his adulthood trying to save. The boy was a born sacrifice. But why he, Snape? Why did he have to be the cold one, the strong one, the one who saved face? When would it be his turn to allow his love to consume him and the work he lived on for? If there were a divine maker, it seemed the only just reward for a lifetime of subverting his own happiness for the sake of humanity…..well, her.
He gave Harry some last tips for success, and a threat for good measure: "I shall know if you have not practiced." The door closed behind the boy's retreating back, "Please succeed at this, Potter," Snape whispered to the space behind his eyebrows. "Please, Potter, just keep Him at bay so I can protect you."