Severus Snape was a curious being. It was usually hidden under layers and layers of unpleasant characteristics when he related to people, but it was there. The reason why he got so interested in the dark arts in the first place, to be able to understand the basics of magic, transcending good or evil. The reason why he got pulled into the Death Eaters' circles, the reason why he was in Slytherin in the first place, other than wanting it with all his might. He was curious. And sometimes his sneaky need would make him forget about conventions or rules.
Charity's owl screamed for him to go and have a look around. So he did, knowing she wasn't there, without asking himself anything about ethics.
He said the words, and he walked inside, a bit wary, raising his eyebrow at the cat, untouched by the aggressive posture. He'd be damned if he got scared of a cat, he could endure much worse pain than claws at his ankles. "Whatever, kitty." he said and closed the door, a bit more confident as he started pacing the room, looking around.
Lots of pictures... family... family... who's that? he wondered, taking up a frame and frowning at the couple, Charity and a young... muggle he would say.