Beckett is bent over her desk working on paperwork when Castle slides into his chair next to her desk.

"Miss me so much you came to help me with this paperwork?" she asks, without looking up.

He fidgets next to her and she can tell that something is up, something she's probably not going to like.

"No, I came to ask you about your opinion on Ethan Slaughter."

That gets her to look up. "That asshole who works the gang unit?"

"Glad to know you think so highly of him," he mumbles.

She rolls her eyes shuffling to the next page of her paperwork. "Why do you care about Ethan Slaughter all of sudden?"

"I saw him on TV this morning. Thought about doing some research with him," Castle shrugs, running a hand over her parade of elephants.

Beckett glances in his direction and then back down at her desk. "Nikki going undercover in a gang unit?"

"No, I'm just," he starts, squirming in his seat, "trying on a new partner."

She puts her pen down and gives him her full attention. "I'm sorry, what?"

"Sooner or later people are going to find out about us," he tells her. "There's no guarantee that Gates is going to allow us to continue working together. I have to be ready to move on."

"I don't want a new partner."

He reaches out for her hand but draws back when he remembers Ryan and Esposito are sitting right behind them. "I don't either. You guys are my team, but we may not have a choice. Would you rather have me as your partner or your boyfriend?"

"I'd rather have you as both."

"Beckett –"

"Just go, Castle," she tells him looking back down at her paperwork.

"Beckett it's not like I'm –"

"Don't you have some gang violence to go deal with?"

Castle sighs and stands to leave.

"I'll see you later?" he asks.

She waves him off, not bothering to watch him make his way out.

"I feel like he's cheating on us," Ryan comments as he watches Castle and Slaughter laugh on the other side of the precinct.

"More like cheating on Beckett," Esposito snorts.

She glares at him. "Can we focus please? We have our own case to worry about."

"You were talking to him earlier," Ryan starts. "Did he tell you why he was doing this?"

"Research," Beckett grumbles, writing a note on the murder board.

"This is really ticking you off, isn't it?" Esposito asks.

"I'm not his keeper," she says, capping the whiteboard marker. "He can do whatever the hell he wants."

"But it's bugging you," Ryan adds. "Seeing him partner up with someone else."

She spins to glare at the both of them. "What's your point?"

Esposito shrugs. "I just think it's interesting."

"Yes, very telling," Ryan says.

Beckett brushes past them, heading to her desk. "Just get back to work."

"How's your case going?" Castle asks, staring up at her murder board.

"How's yours?" she retorts, walking away from him.

He grabs her arm and pulls her back to him. "Remember what we said about communication?"

"Fine, you want me to communicate? You need to stop. You're going to get yourself killed."

"No, hey I'm fine. Slaughter –"

"Doesn't give a damn about you. He doesn't have your back like I do."

"He's not just going to let me die," Castle tries to tell her. "He would have to deal with the repercussions."

Beckett shakes her head. "Remember that paper you signed when you first started following me around? The NYPD is not liable if anything happens to you. I care if you live or die. Slaughter does not."

"Kate, I'm going to be fine. You worry too much."

She walks away from him again to her desk and comes back holding a file. Beckett hands it to him.

"What's this?" he asks, flipping through it.

"Help with your case. Like I said, I have your back."

"You didn't have to do this."

"Of course I did. That's what partners do."

Castle sighs. "Beckett, I'm sorry."

"Yeah, I know."

She's just about to crawl into bed when she hears the knock on her front door. She pulls her robe tighter around her and grabs her gun before moving to answer it.

"It's been a while since you've greeted me with your gun," Castle says. "I thought we'd moved past this."

She groans and moves aside to let him in. "What are you doing here, Castle?"

"I just wrapped things up with Slaughter. Thought I should stop by and apologize."

Beckett moves to put her gun away and he trails along after her.

"Kate, I don't want to work with anyone else either. If I can't work with you, I'll just…stay home and write or something. I'm only interested in playing cop if you're the one backing me up, er if you're the one I'm backing up?"

She crosses her arms over her chest and leans back against the wall.

"Come on, how long are you going to stay mad at me?" he asks, moving to stand in front of her and placing his hands against the wall on either side of her head.

"As long as I see fit."

"Kate."

His hands fall from the wall and wrap around her hips, pulling her into him. He can feel her trying to resist, but for whatever reason she caves and leans into him.

"Me not wanting you to die is not worrying too much," she says into his shoulder.

Castle's hands move from her hips and press into her back, drawing her even closer. Her hands snake behind him and hold onto his shoulders.

"Well I appreciate that you value my life."

"I don't like the thought of being replaced," she says softly. "As your partner or even, I can't believe I'm saying this, as your muse."

"I'm not going to replace you. I'm going to stay right here until Gates kicks me out."

She looks up at him. "I don't think she's going to kick you out of my apartment."

"Okay smartass," he laughs.

Beckett smirks and rests her head back against his chest.

"Do you know what I think?" Castle starts. "We need to go out on a date. Get out of our apartments and do something besides go to the 12th and crime scenes."

"And that will help me be less mad at you?"

"Aren't you already less mad at me?"

She hums. "Maybe a little."

"Look, I'm sorry. I didn't do all of this to upset you, I was trying to help in a way. It just sort of backfired. So let me make it up to you. Let me take you out."

Beckett pulls away to look up at him. "Okay fine. Impress me."

Castle grins. "I will. I'll take you to my favorite place in the city. Do you think your case will wrap by tomorrow?"

"It should. We know who did it. It was just too late to get an arrest warrant tonight, so we'll get him tomorrow."

"Good. Get ready to be amazed."

"Are you going to tell me where we're going?" Beckett asks as she walks hand in hand with Castle down a sidewalk.

He had already taken her to a restaurant that was way more expensive than it needed to be. When she questioned it being his favorite place in the city, he told her that is was just someplace new he'd been meaning to try. His favorite place was some sort of surprise he refused to share the location of. Honestly, she was surprised he didn't have her blind-folded.

"You'll see when we get there. That's the point of a surprise, Beckett."

"Well maybe I don't like surprises."

"Who doesn't like surprises?"

She clucks her tongue. "Lots of people."

"Just not you. I know you, Kate Beckett. Don't forget that."

She sighs, finally giving into the fact that he's not going to tell her. Beckett rubs her thumb over the back of his hand and laughs when it sends a shiver down his spine.

"I bet Slaughter can't make you shiver like that," she teases, still laughing.

"I wouldn't want him to."

"Better stick with me then."

"I already told you that I plan to."

Castle comes to a stop in front of a tall building. There's no sign out front to indicate what it is.

"We're here," he announces, letting go of her hand and spreading his arms wide in a grand gesture.

Beckett looks around, still confused. "Am I supposed to be amazed by this?"

"Well no. We have to go inside."

He takes her hand again and leads her into the building and over to the elevator. The doors open and he hits the button for the top floor. When the doors open again and they step out, it still looks like any regular old building to her.

"Castle –"

"Hold on, we're not there yet."

He guides her down the hall, pushing open the door to the stairwell.

"Go up," he tells her.

"But I thought this was the top floor."

"Trust me."

Beckett pushes past him and climbs the stairs up as he instructed. The stairs end at another door which she pushes open. Castle is right behind her, moving a cinder block to keep the door propped open. She steps out onto the roof of the building and the view nearly takes her breath away. There's a string of twinkle lights hung overhead, but they nearly blend in with the lights of the city all around them.

Castle comes up behind her, wrapping his arms around her waist and resting his chin on her shoulder. She leans back against him.

"This is my rooftop," he tells her. "I discovered it years it ago with Kyra. It used to be our spot, but I figured it was time I share it with someone else since we've both moved on. We used to come up here on warm summer days and she'd read while I scribbled in a notebook. After she left, I started to come up here just to think. I'd come late at night and lean on the edge and just watch the city below. I spent a lot of time up here last summer."

She twists to kiss his cheek before she wanders away from him to look out over the edge.

"It's beautiful up here."

"I told you, you'd be impressed," Castle says, moving to stand next to her.

Beckett looks over at him and smiles before looking back out at the city.

"God, I love New York," she breathes. "I love being able to look at it like this. To take a step back and not look at it like a cop, to not see all of the crime and the hurt. But just to see it as the amazing city that it is."

Castle drapes an arm across her shoulders and she leans into him.

"Thanks for sharing your rooftop with me, Castle."

"Of course," he says kissing the top of her head. "I knew you were just the type of person who would appreciate it."