And so "The Great Escape" begins with knowledge. Really, Ginny is totally incompetent at opsec to have written that down with no "eyes only" or other protective spell. If Dumbledore is getting new members like that, it's no wonder he's losing to Tom. Good moves on Hermione's part, though.
It's a well-done bit of back story, too, that succinctly, but fully, explains how the situation in the first chapter came to be. Methinks there're going to be a lot of embarassed "Light" figures when this is over and the dust settles.
Author's response
I've always been in the 'back story is the real story' camp. Back stories tell about people.