OMG I just heard a
brilliant theory on PotterCast that has pretty much turned my brain to mush.
In an email,Angela (?) states that she believes Harry will have to return to Godric's Hollow the night his parents died. He will witness something there that will help him defeat Voldemort.
She says that Harry is the "other person" at Godric's Hollow and the
he is the one who gives Dumbledore information. This is how Dumbledore knew what to do with baby Harry and why he let him face dangers at school. Because he knew he would survive.
This would be difficult for Harry because he would want to save his parents but if he did it would change the world as he knew it.
Now maybe Snape was there and had some sort of confrontation with Harry and this is why he hates him so much.
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So maybe Harry return to GH to see exactly what happens to Voldemort. We know that Lily's sacrifice is what saved Harry but we don't know how or why. Perhaps he needs to view what his mother did to cause a flaw in the killing curse.
And if he confronts Snape, who might have been more on the bad side then, Snape might be forced to make a Fidelius Charm/Unbreakable Vow so he cannot tell Voldemort about Harry.
In killing Dumbledore, he will have been released from the charm or vow.
Harry will be in a race against time trying to defeat Voldy before Snape leaks information. This is assuming that Snape is not on the good side. Unfortunately, we don't know where his loyalties lie.
This is all I got. What do you think?