This post contains frank discussion of several plot points from Season 8, Episode 4 of Game of Thrones. If you’re not all caught up, or would prefer not to be spoiled, now is the time to leave. Seriously: this is your last chance, and you won’t have another so, get out while the getting is good.

The heartbroken, crying Brienne of Tarth was truly all of us as we watched Jaime Lannister ride away from both Winterfell and his tidy little redemption arc. Jaime is on his way back to Cersei’s side in a decision that will, surely, cause his downfall. This decision not only goes against the wishes of Brienne and Jaime fans who would prefer those two crazy knights survive this war together; it goes against what we understand to be Jaime’s reaction in a similar situation in the books. We’ll get to the books in a bit, but speaking to Vanity Fair last summer, Nikolaj Coster-Waldau explained the reason behind Jaime’s big decision.

Over the course of eight seasons, Game of Thrones has continually stripped each of Jaime’s defining characteristics. His stature in court, his fighting hand, his crop of golden hair, his tense relationship with his father, his even tenser relationship with his kids, his bad reputation, his good reputation: by now, all of that is gone. All that was left of the villain who opened the series by pushing an innocent kid out of a window was an improbable hero who had nothing left to do but try to build something new. But he couldn’t, and that will be the tragedy of Jaime Lannister.

“Can we redefine ourselves?” Coster-Waldau asked himself as he approached this final season. “Most people have moments in their life where you go, ‘Can I really, fundamentally change?’ . . . The core of him has always been Cersei. . . . When that’s taken away, what are you then? What’s left? Is there anything left? When he leaves [King’s Landing at the end of Season 7], obviously he has no idea. He doesn’t know the answer to that question.”

Leaning on his own long marriage—which the actor stresses with a laugh is nothing like the Jaime/Cersei relationship—Coster-Waldau planted the seed that Jaime might find himself headed back to Cersei in Season 8. He explained the subtext of Jaime’s goodbye to Cersei—“I don’t love you anymore. . . . I’m calling your bluff, and, you know, you can’t hurt me now because my heart has been destroyed by you. You can’t hurt me anymore than you already have”—may not stick.

That’s, of course, said in a moment of passion. Who knows if it’s true? I’ve almost been married 20 years—June 6th will be our 20th anniversary—and I’m very, very lucky. I have a wonderful wife. But over 20 years, there are times where you have fights. You can be so angry that for a second in your passion and anger you can go, ‘Oh, fuck this.’ Of course, three seconds later, you go, ‘No, no, no. What am I doing? What am I thinking?’ . . . I think the fundamental emotions are the same in every relationship. As a setup for the season we’re shooting now, it was just amazing.

But if Jaime’s decision to have sex with Brienne and then leave her feels like such a swift reversal your head is still spinning, Coster-Waldau is sympathetic: “We’re used to having a whole season to get to a point. Now suddenly, a lot of things happen very quickly.” The actor says he has to fill in a lot of the details for himself:

Trying to connect the dots between the scenes was a little complicated because you invest so much time, so many years in these characters, so when suddenly you find out that Jaime comes back and his son has committed suicide . . . there’s so many things that obviously you can’t go through, on-screen, all of these moments, but you have to still walk through them in your mind, if you’re an actor, at least talk about them. There was a lot of those connecting the dots throughout.

Jaime’s narrative arc in the books left off a while ago relative to the show, of course, but it included a Jaime moment that fans hoped would make it to the show. In A Feast for Crows (2005) Cersei writes to her brother pleading for his help during her trial at King’s Landing and Jaime, presumably on a road to something healthier, denies her.

Qyburn’s words were terse and to the point, Cersei’s fevered and fervent. Come at once, she said. Help me. Save me. I need you now as I have never needed you before. I love you. I love you. I love you. Come at once.

Vyman was hovering by the door, waiting, and Jaime sensed that Peck was watching too. “Does my lord wish to answer?” the maester asked, after a long silence.

A snowflake landed on the letter. As it melted, the ink began to blur. Jaime rolled the parchment up again, as tight as one hand would allow, and handed it to Peck. “No,” he said. “Put this in the fire.”

Some Jaime fans had hoped that his farewell to Cersei in the Season 7 finale was the show finally giving us the Lannister twin break up we deserved. At this point in Martin’s narrative, Jaime has yet to reconcile with his estranged sister. But who knows what the author has in store for Jaime in the long run. The show itself certainly teased this potential reconciliation between the Lannister twins in Episode 2 when Tyrion told his brother:

Jaime himself—with an assist from Bran—prepared us that this was something he was capable of:

So the bottom line is this: Jaime is an extremely honorable and loyal character. He promised to fight for the living. Keeping that promise was enough to inspire him to break from Cersei. But that oath to Brienne and to the North fulfilled, he’s now reverted to another oath: the one he swore to Cersei that it would just be the two of them against the world. Does that mean he dies in her arms? Does that mean he kills her? Do they die together? It’s too early to know for certain, but whatever he’s headed towards can’t possibly be good for him. So if you want to talk about tragedy in Game of Thrones talk about Jaime Lannister a man who came so close to being the hero he always wanted to be and fell back on old habits anyway.

More Great Game of Thrones Stories from Vanity Fair

— Here’s who we lost in the great battle of Winterfell

— Was that battle literally too dark? The director of photography weighs in

— After Arya’s unexpected move, what happens next?

— Even Maisie Williams didn’t see Arya’s move coming