[Oh, you know. A good servant doesn't do things for his own satisfaction or curiosity. At least not when people can see, or when he can't cover it up as something else. In this case, however, it really is more for Ciel's sake, for the sake of finding a way out (hope springs eternal), than Sebastian's own curiosity.
He makes no comment on being called out - his eyes widen momentarily, but then he just smiles. It's kind of entertaining, the way she doesn't buy it yet never seems to mind his word games... or what the fact that he's playing them implies about him.]
Indeed. The very structure of it, the entire set-up... [with the monsters increasing in dangerousness and all] It's easy to assume there is something hidden within.