He can't leave the room. Her room. And it's all the Order's fault. Confined to a small space with only the Mudblood for company, something's going to give. Maybe his sanity. Maybe not. "There," she spat. "Now your Blood's filthy too!" DM/HG. PostHBP.

Hermione overhears something she shouldn't concerning Professor Snape and decides that maybe the House-elves aren't the only ones in need of protection.