Castle Finale: Will Rick 'Blow Up' His Relationship With Kate to Save Her?

This Monday at 10/9c, in the Season 4 finale of ABC’s Castle, the murder of an Army veteran puts Kate (played by Stana Katic) on the trail of the man who shot her – meaning she’s perilously close to revisiting the murder of her mother. But Rick (Nathan Fillion) has privately vowed to steer his partner away from that conspiracy-laden powder keg, lest he lose her — forever.

Will Castle be forced to reveal the secret agenda by which he has been operating – and thus be punished by Beckett for a perceived betrayal? Could this finale serve up the biggest blow to the “Caskett” relationship… or, somehow, bring them closer than ever?

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Circling back to the unsolved case of Johanna Beckett’s murder for the Season 4 finale is by design, says series creator Andrew W. Marlowe, since that story point always goes hand-in-hand with significant movement – sometimes for better, other times for worse — on the Rick/Kate front.

“Beckett is at her most raw when she’s dealing with her mother’s murder,” Marlowe tells TVLine. “That’s when she’s most emotionally vulnerable, even from the first time we touched this ground in Episode 10 of our first season, where Castle starts looking into [Johanna’s] murder and causes their first rift. And at the end of Episode 213, ‘Sucker Punch,’ we have a very nice scene where Beckett accepts Castle’s presence – like, ‘I kind of want you around. I like you pulling my pigtails.’ Their emotional trajectory has always been intertwined [with the Johanna Beckett case].”

The big difference this time around, however, is that to temper Kate’s dog-with-a-bone nature when it comes to this case, Rick may have to reveal what he knows – that she will get herself good and dead – if she doesn’t back off. And to let loose with that secret could be devastating.

“In a lot of ways, it is Rick’s greatest fear,” Marlowe says of Kate’s pursuit of the sniper who shot her. “Not only for her safety, but because it might press him to reveal something that could blow up their relationship. He’s been keeping this pretty big secret from her and he knows what the stakes are. But he also knows it’s the only way to save her life.

“So that’s what we wrestle with in the finale,” the show boss continues. “Whether a relationship or even trying to have a relationship with somebody [who keeps secrets] is going to be worthwhile, and how Beckett, once she learns of that betrayal, is going to process it.”

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One thing is for certain: This season finale stands to be a formative one for the ABC drama, so I asked Marlowe what sort of reaction he got from his series leads upon laying out the story before them.

“Late in the season, I sat down with both Nathan and Stana to talk to them about the trajectory of the end, starting with ’47 Seconds’ and Kate’s secret coming out, so they had context for all those scripts, what the basic moves would look like and how we were going to resolve this season,” he recounted. “And when the [finale] script came out, I checked in with both of them to get any and all reactions, because at that time in the season we want the performances dialed in. If there are any questions ahead of time, we want to make sure we address everybody’s comfort levels and concerns, all that sort of stuff.”

All told, Marlowe shares, “There was a lot of discussion about what we were choosing to do, and everybody felt really good about it – that the way were handling it was the right way to handle it for our show.”

Castle fans…. Are you ready for the finale?