It was only one button less than usual. There was nothing inappropriate about it, nothing he could dock points for. It was, however, driving him crazy.

Could he force her to do up that top button?

Of course not, he could be misunderstood as looking too closely where he shouldn't. And it wasn't as if he had looked more than that one off time. After all, it was rather impossible to answer a student's question without even glimpsing anything in the vicinity of their face.

But Merlin, if anyone found out what thoughts were racing through his extremely dirty mind….

….

Thanks to Lauren (peanutilover) for the idea. (Just in case any of you couldn't tell, Snape's talking about Hermione.)