This is lovely! Severus's younger version broke my heart. Oh, and Tom Riddle, that was horrible -- and horribly ironic. Wonderfully original explanation for the doe Patronus. I also enjoyed Hermione's character as an Unspeakable who will bend the rules to 'speak' to Harry and save Snape.
Sorry if this review is disjointed: I just kept remembering the parts I loved all of a sudden.