User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-12300635-20130921224853

Here's my theory. (I know some people are going to think it can't happen but I don't care)

I think Percy and Annabeth are going to be captured by Gaea, but then when they're about to be sacrificed, Percy uses the Eye of Horus mark he got from Carter, then Carter shows up and they all escape.