Read this little interview from Ryan murphy today -
I wanted to do something that started at 1 and goes to 10. Cordelia becomes quite unhinged, and quite dangerous, and perhaps the most deadly of all the witches. Something heinous and absolutely horrible happens to her in the Halloween episode, both parts 1 and 2. It spins her around.
If you seen the promo I think it links with a distressed Fiona at the halloween party. I wondered what happens to her that makes her go crazy. Heard she trying to get pregnant maybe she dose and looses it in a typical american horror story way.