Wow. Just... wow. I have no words, and I've just read this three times over in one sitting.
Rufus is my favorite character of the moment, and I always thought JKR & DH didn't really do him the justice he deserved.
Seriously, this story was magnificent, and everything said above holds true. Especially the point about the little details you threw in – Rufus-the-Hufflepuff, that Stan was an idiot but really a Death Eater, Rufus's realization about Snape's possible loyalties, the brilliant characterization throughout the torture scene. The brief description of his injuries in the end had me sniffling because of how true to life they were, harking back to an art of interrogation course I once took. *shivers*
Amazingly well done. I really want to figure out who you are now and go stalk through your stories a while.