This is just a section with some notes about this story. Mostly it's just my thinking process for parts of the story, in case anyone actually cares how I came up with some of the ideas.
I've been wondering for a long time why she was almost spared. Seemed very strange to me. I wrote another fanfic (not good enough to share online) a while back that examined this more closely, and there was only one explanation that seemed to make sense to me.
Begging Voldemort? What evidence is there that begging and pleading ever did any good? She and Voldemort (in their exchange) seemed to be speaking quite familiarly. Very strange, again.
I know many people like Lily, but I just never did. Sorry. We all have our preferences. I'm sure many people hate Snape. It's a matter of opinion and it's best not to argue too much about it.
Peter Pettigrew / Wormtail
I know the whole Harry and Wormtail exchange was basically exactly like the Harry and Voldemort exchange just a few chapters earlier. Sorry! Lack of imagination. But I had to do something with him, because that was the only way Snape would get his hands on Pettigrew, which was rather necessary if he was to sacrifice Harry to Sirius in the following chapter. And I had to get Harry out of the dungeons in some way, or else there would be no way to get Dumbledore, Lupin, and Sirius out of there while leaving Snape alone long enough to hide Pettigrew.
Harry gets away with it the same way Mad-Eye Moody did in Goblet of Fire. Sure, in theory it's a life-sentence in Azkaban for using any of the Unforgiveables, but the Ministry did not descend upon Hogwarts after Moody put an entire classroom full of students under the mind-control curse, so what evidence is there that anything would happen to Harry as a result of using an Unforgiveable against Voldemort? Even without this argument, I doubt that anyone who killed Voldemort would be punished in any shape or form. The likely consequences would be Harry's own conscience (using such powerful/awful Dark Magic), and the reactions of those around him.
As far as how Harry managed the curse at all, I think I explained it as well as was possible. He is about to die. He knows it. He doesn't believe that anything he does will make any difference. But as he sees Voldemort about to kill him, he makes the decision to fight -- even though he knows he can't win. Would it make any sense for him to try to curse Voldemort with boils? No. Under the circumstances there is only one curse he can use, if, like the says, he is going to fight with everything that is available to him.
We know that Harry occasionally pulls out of himself powers/strengths that can't really be explained. It takes real power to make the curse work (as Moody said in Goblet of Fire, all the students could point their wands at him and say the incantation but he wouldn't have gotten more than a nosebleed), but I decided that as he faced certain death Harry managed to find the necessary strength within himself.... just like when he pulled Godric Gryffindor's sword out of the Sorting Hat.
Maybe it doesn't quite make sense... but oh well. I rest my case. There are a lot of fanfics out there in which Voldemort dies, and the simple truth is that it's pretty darn near impossible to kill him off in a way that makes complete sense. My way may be no better, but I hope not the worst possible.
The Potion in Chapter 9 is basically from my own imagination, but with a basis in canon. In the books, there is at least one spell / potion that seems to suggest that the relationship between a father and son (don't know about daughters) is very important. So, I just used some Latin words that seemed to make sense and sounded good, and an exotic plant (yes, fireweed is indeed a real plant!), and made up the potion. Obviously, blood had to be in there, or else how was I supposed to reveal Snape to be Harry's father without using the old cliche of a paternity spell?!
How does Harry figure out the truth?
The same way that adopted children sometimes manage to figure out that they're adopted, even though the truth was concealed. Bits of information float around and around in the brain, until suddenly they just click together. Of course, writing it out is very difficult. How do you really explain the thinking process that would bring someone to imagine the unimaginable?
Remember, he's heard quite a bit in the last few days -- overheard conversations, his talk with Dumbledore, what Sirius said, etc, etc.
Sirius Not Allowed In
Why doesn't Snape let Sirius in?
You mean besides the fact that they hate each other?
One reason he doesn't let Sirius is the same reason that he doesn't want Lupin around. Every time either of them is there, Snape gets pushed aside. The last thing he wants is for them to be hanging around, telling him how to manage Harry.
Dumbledore On The Way?
I know -- confusing.
We know that between the time Harry leaves the castle and the time he comes back, they have time to contact Dumbledore. You can infer that Lupin and Sirius had arrived just before the attack, and Sirius had stayed outside while Lupin went in. Harry just made the worst move at the worst possible time to get himself into the mess that he did.
HOWEVER, there is no evidence (for or against) that they knew by the time they arrived at Hogwarts that an attack was coming. Most likely, the attack began while Harry was missing, and that's when they contacted Dumbledore.
Don't ask. :-)
I just couldn't have ghosts and Peeves floating around Hogwarts, interrupting everything.
I suppose it's possible that the ghosts had left (they seem to be free to move about, it is not a known fact that they're bound to the castle). And it's possible that Dumbledore or someone else got rid of Peeves. Maybe Snape. Who'd want to be spending a summer at Hogwarts and have Peeves around?
Filch is gone because like all the rest of the staff he is free to leave during summer. There is no evidence that he doesn't have a home somewhere.