So long, Lady Stoneheart
Speaking of the Brotherhood, an appearance by Beric Dondarrion suggests that Lady Stoneheart, a resurrected, bloodythirsty version of Catelyn Stark intermittently seen in George R.R. Martin's books, won't be making it to television. Like Jon Snow, Beric is one of the few Thrones characters with the ability to come back to life, thanks to some love from the Lord of Light. This is established on the show -- recall the time Sandor bested Beric in a duel many moons ago -- and comes up again this episode when the Hound takes his vengeance on Lem Lemoncloak and pals.
But Beric being alive at this point in the story is a departure from the source material; in A Feast for Crows, Brienne discovers that the Robin Hood-like figure sacrificed his life to bring Catelyn back to life. If he's still around, that means Catelyn (who becomes known as Lady Stoneheart after her resurrection) isn't. When Thrones hammers home that Catelyn Stark is dead, dead, dead in the conversation between Jaime and Edmure Tully, it's also suggesting this theory is also dead, dead, dead.