Castle

It's been a stressful season for Castle fans dying to see author Richard Castle (Nathan Fillion) and his muse, Detective Kate Beckett (Stana Katic), become more than friends and partners.

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They kissed. They held each other tightly as they nearly died together in a freezer. They shared a giant Los Angeles hotel suite that, despite its roominess, couldn't contain the sexual tension. And in Monday's finale (10/9c, ABC) all of those issues will be addressed.

"Both characters lay their cards on their table," creator and executive producer Andrew W. Marlowe tells TVGuide.com. "[They] come to an understanding about the issues that they're dealing with and the ways in which each of them were approaching the relationship. There's a knockdown, drag-out fight where Castle's like, 'Look, what do we mean to each other?'"

Unfortunately, this meeting of the minds comes just as Beckett once again goes down the rabbit hole chasing her mother's killer. When sniper Hal Lockwood (Max Martini) — who killed Beckett's last solid lead earlier this season — escapes from prison, the case is re-opened. And some of the new information hits far too close to home.

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"This is Beckett as her rawest," Marlowe says. "Not everything that she thought was true is actually true. She has to confront some very serious issues in her own life and in her relationships when the truth comes out. She doesn't really like what she finds, but she's going to keep going, even though it puts her in danger."

And that danger isn't just limited to Beckett. Marlowe confirms that before the season ends, one major character will be in a body bag, and he says the early Season 4 renewal made it possible to take such risks in the storytelling.

"Knowing that we're not in a position where we have to resolve everything and that we can push ourselves into deeper mystery and more complicated relationships allowed us to embrace this kind of story," Marlowe says. "It was something we started looking at early in the season, and then after we were renewed, I felt very comfortable moving forward with it.

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"It's always uncomfortable for any show creator to have to end a relationship with somebody they've created along the way," Marlowe continues. "But sometimes to challenge your characters for the continuation of the show, it's an important thing to do."

While we're fairly certain the show wouldn't kill its female lead, Marlowe insists that Beckett's recklessness is a major concern. "Everybody knows that in pursuing this case, she's basically running in the way of the bad guys and it's going to get her killed," Marlowe says. "So everybody that cares about her is just trying to protect her. At the end of the day she cares too much about this case to be protected. [She's] pretty much pushing everybody away."

Castle's Season 3 finale airs Monday at 10/9c on ABC.