I have a question for those of you who read the books (and if you haven't, this might be in the nature of a spoiler):

Having read through Book Five, and I simply don't remember the "reveal" that it was Lysa, in cahoots with Littlefinger, who poisoned Jon Arynn. I have always thought that the killing of Jon Arynn was entirely a Cersei Lannister action in reaction to Arynn's discovery that her children were incestuous-born ("the seed is strong").

Did I miss this important point from the books?