^This is totally not a spoiler, since you know this moment has been coming for over a season: The Wildling Army attacks The Wall. Lots of cool stuff happens, at least in the book. There are two moments that when the show was first started that I figured they would not be able to pull off: The attack on King's Landing and this. Given that they did a great job with the first, and that the same director that did that episode (Blackwater) is doing this one, I have high hopes for an amazing hour of television.
I will also say this: if the season finale (episode after this one) ends the same way Book 3 does, the screams will be heard around the world.
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