Remus Lupin

All the more reason for me to go. We need someone up there whose only job is to look after Harry. And Hermione as well.

Raz Lestrange may be a cracking duellist but he's got lessons to teach. And he sure wouldn't give a thought to sacrificing Hermione if it meant saving Harry.

Merlin, there are a hundred reasons Snape could want to get Hermione alone. Polyjuicing into her to get to Harry's just the tip of the wand; he could hope to ransom her to bring Harry to him; he might want to use her blood or bone for spells - I don't want to say anything where she'll see it, of course, and frighten her. But I don't like it one bit and I'm not letting Poppy Pomfrey tell me they'll take care of things up the school.

They've taken care of things so well, this far.