Severus was working on his next submission to the Potions Journal when Potter slammed in without knocking.
"What did you do?!" Potter demanded, slamming a folded page of Muggle paper onto the Potions Master's desk.
Severus looked up calmly and made a conscious choice not to take points for the flagrant disrespect in the young man's address. "I'm afraid you will need to be more specific, Mister Potter."
The Gryffindor scowled. "I just got a letter from my relatives apologizing for abusing me, and a box filled with enough gifts to make up for the last sixteen years. I know it was you!"
Severus raised an eyebrow curiously. He honestly didn't know how the Gryffindor could have figured out that he had brought these events about.
Potter straightened and crossed his arms over his chest. "Mrs. Weasley doesn't know enough about my past, Dumbledore wouldn't do anything to jeopardize his position at the school, and you disappeared just last weekend. Not to mention, you're the only person I know who is threatening enough to frighten my relatives without fear of retaliation. What…did…you…do?"
Severus struggled with the desire to smirk, and lost the battle. He felt the corners of his lips twitch slightly upward. "I haven't done anything, Mister Potter. You could ask your relatives, and I'm sure they would tell you that they came to this realization wholly on their own, after a little soul-searching." He wasn't sure how Potter would react to this blatant lie. He was prepared to turn the tables and use his position as the young man's professor to force him from his office without answers. It may cause a rift greater than any they had previously harbored, but he had never expected Potter to be angry over his relatives' change of heart.
Rather than continue in his anger, Potter actually laughed, though he tried to stop it. "Soul-searching? That's the most ridiculous-" Another harsh laugh burst from his throat, and he stopped, bent over, as his lung struggled to draw air in-between chuckles. It took several moments for Potter to recover, and when he did, he stood up while wiping tears from his eyes. "Okay, never mind, just forget the 'how'. Why did you do this? I never asked you, or anyone else for that matter, to step in."
The Potions Master seriously considered lying again, feigning total innocence, but decided that, while Potter never needed to know what he had done to those monsters, he deserved to know why.
"Because you should never have had to ask, in the first place," Severus explained softly. "You deserved better from them, not because you are the Boy Who Lived, but because you're their family."
Potter's laughter faded, leaving behind a soft smile. "Thank you. I don't approve of whatever it is you did to them. I never wanted them to be punished, in part because I never thought it would do any good, but I do appreciate that you made the effort. So, thank you."
Severus allowed a soft smile of his own to replace his smirk. "You're welcome, Mister Potter."
Their gazes each softened in a shared look that would later baffle Severus, before Potter turned, taking up his letter. As he moved to leave the Potions Master's office, residual chuckles shook his body. Severus heard the Gryffindor mutter as he pulled open the door.
"Soul-searching, what a concept."
Severus couldn't help his own small chuckle and returned his attention to his 'essay' for the Potions Journal. A stray thought, that Potter had looked fairly attractive in his new clothes, skittered across his mind, just out of reach of conscious thought.