Nathan Fillion, Stana Katic

Castle's Detective Kate Beckett has revealed a lot in her shrink's office this season.

Castle's Stana Katic: Sniper case brings Castle and Beckett closer to a relationship

In the Season 4 premiere, Beckett (Stana Katic) confessed that she remembered everything about her near-fatal shooting, thus revealing that she'd been lying to Castle (Nathan Fillion) about hearing him say, "I love you." But in the show's most recent episode, Beckett told her therapist (Michael Dorn) that she's ready to move past her mother's murder and be defined by a real relationship.

"She is moving towards trying to get some clarity in her life," creator Andrew W. Marlowe tells TVGuide.com of how far Beckett has come so far this season. "She is coming to an understanding about how deeply she is affected by all this stuff. ... She is starting to understand the reasons why she is driven to do the things that she is driven to do, and she wants to be able to push past that and take a step into a bigger world emotionally.

"Castle is not just a passing fancy or one-night stand for her," Marlowe continues. "So if she is going to jump in, she wants to make sure that she is ready to have the right kind of relationship. It is nice to see her moving in the right direction."

Check out photos of the Castle cast

Even so, fans shouldn't expect an instant hookup between Castle and Beckett. And yet, in Monday's episode (10/9c, ABC) the two will be hooked up — with handcuffs. In the aptly titled "Cuffed," Castle and Beckett wake up together only to realize that they've been bound in a mysterious surrounding with no memory of how they got there.

"We wanted to have fun," Marlowe says of the episode. "We wanted to actually put the two of them together and have them physicalize certain aspects of their relationship. And we got to see them being a little playful with each other even though the situation seems like it is dark and difficult. 

"We wanted to see the two of them working together and finding that rhythm," he continues. "The whole context of the episode is what it means to have a successful relationship and what it means to be in sync. ... Castle and Beckett start the episode out of rhythm and find it as they move forward. It's just our way of showing the audience the progress that these guys have made and their ability to work together to resolve the situation."

Castle Boss: Castle and Beckett's new secrets are a "ticking bomb"

And even though this is the show's last episode before the holiday break, Marlowe assures us that the couple will still be in sync when the show returns in January. "There are always going to be interesting challenges that we confront ... their relationship with, but I think they've found a pretty decent place," Marlowe says. "I think that we all know that they're working for the same goal."

But? (There's always a "but," isn't there?)

"We also know that this season they're keeping some secrets from each other," Marlowe teases. "And those are going to have to be dealt with. They'll start coming up as we get into the spring. That ticking time bomb is always there."

Castle airs Monday at 10/9c. Watch a "kinky" clip from "Cuffed" below: