Although I am told not in the books, the dynamic between Tywin Lannister and Arya Stark is very good. At this point, Tywin has figured out that Arya is "high born," and some people are speculating whether he'll actually find out she's a Stark or whether she'll slip away somehow.

The Battle of Blackwater will be portrayed in a few episodes. I heard a rumor that they were saving "battle budget" for this episode, but we'll see.