In my story, which I'm still editing, Snape is the one to uncover the fake Moody in the end of book four. He wouldn't want to give himself away as past spy, and yet he wouldn't want to seem loyal to Dumbledore with Voldemort having returned. (Him finding out Moody will have happened after Voldemort returns). How can he go about uncovering Moody?
I'm in a bit of a pickle, and ideas are welcome!