I can fully understand why people want to know the basic details of Advent Children's plot - who the lead characters are, the names of the antagonists, the details of the new crisis. But when people start to pre-emptively dissect the entire plot, and try to find out every detail - including all the secrets and surprises - then it kind of defeats the purpose of watching the movie at all.

"Hey, I hear there's a book coming out soon - it's called The Lord of the Rings, and it's about some dudes who have to destroy a magic ring in order to save the world.

So, who's going to destroy the ring, and who'll die and who'll get married in the end? WE NEED TO KNOW NOW!"
This kind of thinking is what's going to ruin Advent Children.

*By the way - the first two paragraphs of the first post in this thread are pure sarcasm.