"The End of the Affair" is a heady episode of television, using flashbacks to 1920s Chicago to introduce a multitude of new plots. First, there's the retcon-y part of Klaus being friends with Stefan back then which dredges up Stefan's bloody past. This leads to more questions from the past--who Rebecca is, what her necklace does, and what she knows, who was hunting Klaus and his sister--and we can see how dense this material can get, filling the season. Now that Klaus restored Stefan's memory of this time, how will he change?
Elena and Damon headed out to Chicago and Elena comes face to face with Stefan--twice! I was already surprised when Stefan saw her in the hidden compartment, and even more when they actually talked and Stefan told her he wasn't coming with them. What's great about this is that Elena and Stefan being apart isn't physical, as if Stefan couldn't be found, but because Stefan's mind is somewhere else right now. With Rebecca's return it looks like Stefan and Elena won't be getting back together anytime soon. Which is fine because there are 19 episodes left this season, plenty of time to tell more story.
There was just enough time in the episode for Caroline to get screen time and conclude her captivity. There are obvious parallels to gays as Caroline is tortured by her father who believes she is a monster, and while it's not all that original, it feels less forced than in True Blood. Liz explains that this way of thinking has been passed down through the generations, so it makes sense why everyone would act the way they did.