Snape's completely impenetrable here. It makes me want to see the whole thing replayed from his point of view.
Ooh, write it! Please! Because my trouble is, when I write from one character's point of view I actually don't necessarily KNOW what the other is thinking. (I've also discovered that I can only write Snape's POV from first or second POV, and not third. Whenever I'm in third, it's someone looking at Snape from outside.)