ABC’s Castle, in its Season 4 finale, pulled the trigger on the hook-up that many fans had avidly longed for, when Kate (played by Stana Katic) – having been put through the professional wringer, ultimately resigning from the NYPD – grabbed hold of her personal life and professed her feelings to Rick (Nathan Fillion).

“[Maddox] got away and I didn’t care,” Beckett, in from the rain, shared with her partner in crime solving. “I almost died and all I could think about was you. I just want you.” And then… you know the rest.

So what happens now? TVLine’s in-depth look at the ABC hit’s coming season continues with my Q&A with series creator Andrew W. Marlowe, conducted in the 12th precinct’s newly expanded interview lounge as the cast filmed the season premiere airing Sept. 24.

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TVLINE | Here you are, entering your first season with Rick and Kate as a couple…. How is that different for you?

Given where they are in their relationship, we’re looking forward to mining that fun. Everybody’s asking, did we reach some sort of conclusion at the end of last year? And to all of us it really feels like a new, fresh, fun beginning for these folks, because Castle and Beckett aren’t going to change who they are. They still get on each other’s nerves. And just because you’re in a relationship doesn’t mean it goes smoothly. There’s a finish line that they haven’t reached yet – how are they going to be able to get there? And what’s the roller coaster ride going to look like? Those are all the things we’re really excited to play with.

TVLINE | Stana was saying to me that you’ve got two people who individually are extraordinary, coming together in a relationship. And as many reasons as there are why that’s so right, there’s probably a hundred reasons we haven’t even thought of why it might not work.

Certainly if you look at the relationship on paper — a New York City police detective who lives in a particular kind of socioeconomic world and deals with a particular kind of stuff, and a wealthy mystery novelist who lives in a much different world — these guys wouldn’t make any sense. But oddly enough, it’s their love of solving the mystery where they connected. The sparks that fly between the two of them that are so much fun come from friction, and friction is both a positive thing and a negative thing.

TVLINE | Exactly how much time will have lapsed when we pick up with the new season?

We’re picking up the morning after. It’s going to be the next day, and we get to see what that looks like and how they both reacted to her coming over and the decisions that she’s made and the situation that they now find themselves in. As with any great moment you have in a relationship, it can’t last, because real life intrudes.

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TVLINE | What debate took place as far as how much to show of their long-anticipated coupling?

There was some amount of debate, but it was important to us to show enough to create the poetry of it. There was a certain point where we had some more material, but we felt like we were overshooting the apex of their emotional… I hesitate to use the word climax, because of its meanings… but their emotional connection is more important than what follows after it. We will deal with what follows when we come back, in a very satisfying way to the audience, but it wasn’t something that we felt like we needed to show. Also, since we were ending the episode with Beckett being under threat [from Cole Maddox], with that the sword of Damocles hanging above her head, we didn’t want to go too far, because then we felt like the pure, raw energy of their emotions would be tainted by that. We were very pleased with how it turned out. We hope the audience was pleased as well, though we know there are people out there who would like to see more.

TVLINE | Is it safe to say Rick has seen Kate’s tattoo?

I think it’s safe to say that Rick has seen Kate’s tattoo.

TVLINE | And Stana told me that we see Beckett’s bed finally – which actually answers a reader question I had.

The new relationships that we’re dealing with this year will allow us to really open up her character in a way that we haven’t been able to, because we’ve always been perceiving it through Castle’s eyes. Now that they’re in this relationship, it opens it up a great deal more — but that’s not to say that there aren’t still a lot of layers to the Beckett onion. She’s still a bit of a mystery and there are going to be certain things that she’s going to hold private — and that’ll be both a source of fun and contention as we move forward.

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TVLINE | As you broke the season’s first episodes with this new dynamic to play with, did you find it easier or harder than you imagined?

I think we found it different. Certainly not easier. The questions we’re asking are new questions and engaging the characters in new ways, so from that point of view it’s harder because we were stretching outside our comfort level. It’s just new. Last year, we felt like we had mined everything we could have with them not being together. So this fresh challenge is really exciting to us.

TVLINE | You’ve been given a new laundry list of things to have at your disposal.

Yes. There are things that we haven’t done, things that are fresh, and things that we can explore. There are aspects to this relationship that we can explore, because we all know that once you get into a relationship, the fun and the conflict doesn’t end. In a lot of ways, the fun and the conflict only escalate.

TVLINE | Right – for example, the next time Rick sees Jim Beckett, that’s got to be a little different.

Well, how about a “meet the parents” episode, where Jim Beckett and Martha and Castle and Beckett are all together at dinner? There’s all sorts of fun stuff we can play with. But also, what happens when you find out a secret that somebody has kept, and now that you’re in a relationship, they’re still keeping it? Or an old boyfriend or an old girlfriend comes to town — how do you deal with that?

TVLINE | So you’re saying there may still be skeletons knocking around in people’s closets?

Well, I think we all have skeletons. Some of us who have been in long-term relationships, there’s probably still stuff that we don’t know about our significant others. I think that there are skeletons in both Rick’s and Kate’s closet.

TVLINE | I’d be curious to see some of Kate’s.

Well, she keeps her cards pretty close to her vest, so that’s why they’re more fun. It feels like everybody knows the same Castle — he’s kind of the same guy to everybody in their life — but you can see that Kate is somebody who plays roles. She’s a particular sort of person to her father, and a particular sort of person to Castle, a particular sort of person to Gates, to Montgomery…. She’s very guarded in situations, and she chooses what to reveal about herself. Now that she’s in this relationship with Castle, is she going to reveal a little bit more? Or is she going to keep her secrets somewhere where she can draw her lines and boundaries? [CONTINUE TO NEXT PAGE]