David Benioff and D.B. Weiss tell THR they've got jitters about next year's episodes: "There are a few sequences that are absolutely terrifying from a production standpoint."

[Warning: Spoilers ahead for Sunday's Game of Thrones season finale, "The Children"]

It didn't seem possible, but Game of Thrones has unleashed an episode that may rival The Red Wedding as among its most talked about ever.

Showrunners David Benioff and D.B. Weiss say they've been thinking about this episode since the series began, and knew one of its key moments — in which Tyrion murders Shae — would be "emotionally much different than in the book," as Shae never loved Tyrion in George R.R. Martin's novels.

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"We knew our Shae would diverge from book Shae the moment we saw Sibel Kekilli audition," Benioff tells The Hollywood Reporter. "Sibel brought such life and intelligence to the part; her intensity inspired us to make the character more complex. Our Shae loves Tyrion, and Tyrion loves her. For us the tragedy is watching these two people trying to kill each other when they love one another."

Here the showrunners talk Tyrion's motivations ("He was mad as hell"), the finale's other big challenges and season-five jitters.

Director Alex Graves has called the finale the show's biggest episode ever. What were you most worried about getting right for the finale?

David Benioff: If we're being honest, we worry about everything. Do you know how many anti-anxiety pills we chew every night?

A long time ago the wonderful writer Ann Patchett was my teacher in graduate school. She said a good story has to have some orange juice concentrate and some water: too much of the former and it tastes disgusting; too much of the latter and it's watery. That was an important lesson and one we've tried to follow in this series. Some of our favorite scenes on the show are the quiet ones with two characters talking. But "The Children" is concentrated. From Stannis' surprise attack to the battle with the Wights to the Brienne/Hound fight to Tyrion's escape and the ensuing violence — on this one we just said, "F— the water."

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I hope Ann Patchett liked it, but I'd bet a million dollars she doesn't watch the show.

D.B. Weiss: In past seasons, our final episodes have often been clean-up — exciting in their own right, but primarily concerned with addressing the aftermath of the momentous events of the episode before. This isn't one of those. The finale of the fourth season is more blow-up than clean-up. In real life, blowing things up is usually a lot easier than cleaning them up, but on TV it's a lot more difficult.

Since Peter is so beloved as Tyrion -- perhaps even more so than the character is in the books -- it must have been difficult to work up to the murders. What kind of story preparation throughout the season (or earlier) did you have to weave in so that moment would work?

Benioff: The murder of Shae, in particular, is emotionally much different than in the book. In the book Shae is a gold-digging prostitute from the beginning. She never loved Tyrion and betraying him came easily for her. But we knew our Shae would diverge from book Shae the moment we saw Sibel Kekilli audition. Sibel brought such life and intelligence to the part; her intensity inspired us to make the character more complex. Our Shae loves Tyrion, and Tyrion loves her. For us the tragedy is watching these two people trying to kill each other when they love one another. If only Tyrion had taken Shae up on her offer at the end of season two, they could be living a wonderful life in exile right now.

I'm losing the thread here, Dan. Some help …

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Weiss: Difficult to be helpful when loaded to the gills on anti-anxiety pills. But I think the preparation for Tyrion's actions at the end of this season have been taking place from the very beginning of the story. Long before, really. In a world as cruel as his, his family was the one place he could have hoped to find security and support — and from the time he was born, most of his family treated him horribly. With the exception of the occasional Joffrey slap, he learned to swallow the anger and resentment that came with this rejection and convert them into the sardonic humor that makes him who he is. But in the face of this season's ultimate betrayal -- his sister trying to have him murdered and his father backing her up on it -- Tyrion decided he was mad as hell and wasn't going to take it anymore.

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You went beyond the books this season, and it was very positively received by fans. Are you able to share if we will see more of that in season five?

Weiss: We try not to talk about what's coming in future seasons, especially while the current season is still airing — and when we're not even finished writing the future seasons. I should probably be doing that right now, actually. The books are the reason we're doing this; they're our road map, and they provide many or most of our destinations. But there are many ways to get to each destination, and some are more appropriate for our show than others, and I am totally losing the thread of this metaphor here, aren't I? Yup. No idea where I was going with that. Destination unknown.

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Benioff: While it's good to hear that those scenes were positively received by the fans, we've stayed away from the message boards and whatnot since season one. Did we mention those anti-anxiety pills? We have to make a show that succeeds on its own terms, and sometimes that means veering away from the books. Some people will be upset by that. Some people will like it. Obviously we hope for more of the latter, but if we ever write a scene (or avoid writing a scene) because we're afraid of pissing someone off, we're sunk. As for season five, we're still figuring out how we can afford everything we want to do. There are a few sequences that are absolutely terrifying from a production standpoint.

Time for another pill …

For more from the episode, read our Q&As with director Alex Graves and Shae actress Sibel Kekilli.

Email: Aaron.Couch@THR.com

Twitter: @AaronCouch