The Final Frontier & Swan Song

"Whatcha doing?"

Castle lifted his head sharply, jolted guiltily. "Nothing."

Kate raised an eyebrow.

"Just..." he held up their journal, their old one, and Kate noticed the new one sitting on the desk in front of him.

"I thought you were working on your outline."

"I was," he answered.

"And then...?"

"I got distracted?" Castle offered, the words coming out more like a question.

"Clearly."

"I'm trying to figure out what to get you for your birthday," he said with a sigh, ran a hand through his hair. "And I'm stuck. So..." he gestured to the journal again.

"And you never thought to, I don't know, ask me?" she teased lightly.

"Well I mean, I wanted it to be a surprise, and then I..."

"Castle," she interrupted, putting him out of his stammering misery. "I think it's sweet."

"You do?"

She smiled, slid onto his lap. "I do."

His arms automatically found purchase around her waist as she settled into him, dropped her head to rest on his shoulder.

After a few minutes, Castle's attention was drawn back to their journal, back to birthday present ideas. It needed to be special; he remembered ages ago telling Montgomery that the best thing to get a woman was something she said she wanted when she didn't think you were listening.

Which was where he was stuck, not only because he was certainly guilty of not listening at times, but also because Kate wasn't overly vocal about what she wanted. Jewelry, sure. She'd shamelessly dropped that hint back when they'd first started dating. Throughout the course of their relationship he'd given her earrings, a bracelet, and, of course, the beautiful diamond ring that adorned her finger. He'd also given her books, a nice pea coat, a beautiful scarf, and countless other items.

And now he was flat out of ideas.

Kate lifted her head to press her mouth to the underside of his jaw and Castle was momentarily distracted by the touch of her lips but she caught his line of sight quickly enough to realize that he was still focused on the journal, on finding the perfect gift for her.

She reached out for the book, settled it on their laps and turned to the correct page. He dropped a kiss on the top of her head, nestled his cheek against her temple as his eyes fell to the page.

Dear Kate,

I'm starting to sound like a broken record here but I can't help myself, because every time I think I'm so completely in love with you and there's no way I could ever love you more, you go and reveal another side of yourself and I fall all over again.

I know you love Forbidden Planet and horror movies and that you read plays. And books. A lot of books. I know you love Temptation Lane and comic books. But it never occurred to me that you'd be a hardcore Nebula 9 fan. It shouldn't have surprised me, really, because I already know you have a nerdy side – and I mean that as a compliment, because I love how you embrace it so unabashedly – but I didn't realize you'd be such a fangirl.

That's part of what I love about you; the contradictions, the surprises. The fact that you're not afraid to be smart and bookwormish (and badass, but that's not the main point right now). You make brainy so incredibly sexy. I'm in love with all of you but I'm pretty sure your mind is at the top of my list.

Because of that, I owe you an apology. It wasn't right for me to make fun of you or of a show that meant a lot to you at a very important time of your life. Even though I didn't think very highly of it, that doesn't mean others can't enjoy it. Once you told me what it meant to you and why you related to it so much, I felt like an ass for bashing it. In much the same way that books can impact readers, TV shows can impact their viewers. After all, isn't that why we like them?

What I'm saying is, I understand. I see why you idolized Lieutenant Chloe, why the show meant so much to you. I'm glad that you found something like Nebula 9 to help guide you through that time of your life. It may not be my favorite show ever, but for you I'd sit down and watch it.

I'm sorry, Kate, for making fun of you and for not being more sensitive, because the truth is, I love every facet of you, all of your quirks. I don't want you to be embarrassed to share any of that with me. I want you to feel like you can tell me anything and open yourself up completely. I want you to be able to trust me with that information. I'm sure the things I said these last two days haven't done anything to help win your trust but I hope I can change that in the near future. I want to know you, Kate. You're it for me. I know you are. I don't want to settle for anything less than all of you. Everything. And you deserve everything from me in return.

I've screwed up in the past but this time I'm determined to do it right.

Love,

Rick

"You're sweet, Castle," Kate murmured, reaching up to trace the angle of his jaw with her finger.

He smiled, bent to press his lips to hers. "Only for you."

She pulled back, rolled her eyes at him.

"What?" he asked innocently.

"You're also cheesy."

"And you love me for it."

"I don't know," she teased, saucy smirk on her face.

"Liar," he accused jokingly.

"Pretty sure of yourself, are you?"

"You bet I am," he replied, slipping a hand beneath her shirt, tracing patterns up and down the curve of her waist. "Because you're sitting on my lap wearing a diamond ring that I gave you."

Her eyes fell to her left hand, lifted back up to his. "Never taking it off, Castle," she murmured.

A giant grin spread across his face, crinkling the corners of his eyes and lighting up the entire room. "I love you," he whispered, lips against her ear as though his words were a secret.

She tilted her chin, captured his lips for a deep kiss. "I know."

Castle smiled into the kiss, pulled away just enough to speak. "Even if I can't figure out what to get you for your birthday?"

Kate laughed then, loud and free. "I mean, birthday gifts are pretty much the only reason I stick around."

He pinched her side with the hand still resting against her bare skin and she yelped, nearly fell off his lap. "Castle!"

With the other hand, he tossed the journal aside dramatically. "Guess I don't need inspiration then, do I?"

"Well in that case, I guess I'll just head to bed alone," she replied, equally melodramatic but enjoying the opportunity to rile him up.

"Kaaaate," he whined, reaching for her as she slipped off of his lap with a sly smile. She was quick but he was quicker, missing her waist but catching her wrist with enough strength to tug her back onto him. She stumbled, off-balance, wound up seated back on his lap with his arms laced around her waist once again.

She snagged the journal, removed one of his hands from her torso and placed the book in it.

He opened his mouth to speak but she beat him to it. "I expect a very inspired gift next week."

Castle raised an eyebrow, sexy smirk on his face, and she felt a ripple of arousal rush through her. "Do you now?"

She just smiled smugly, far too pleased with herself, but sometimes he was just so easy to mess with.

"Read, Castle," she commanded lightly.

He huffed a theatrical sigh, turned the book right-side-up and proceeded to the next letter.

Dear Kate,

I'm so proud of you. So proud. I know you hated those cameras and I know you were really uncomfortable having them in your face all the time, but you were amazing. You were a natural, once you stopped worrying about them and just did your thing.

I know when the documentary is actually released, everyone is going to love you, because they'll get to see you hard at work. They'll get to see how strong and determined you are, how fierce you can be in interrogation and yet how kind you are with the families of the victims. They'll get to see everything that made me fall in love with you, which is why I know the audiences will love you too. Because they'll get to see how amazing you are.

I know you don't like publicity but I'm glad you're getting some recognition. You deserve it, Kate. You work so hard every day and you've helped so many people.

However, I'm glad our relationship has been spared the publicity. Thank goodness the producer was willing to help us out with that. I know it can't last forever. Nothing ever does, and secrets like this have a way of spilling out completely unexpectedly. It's going to happen eventually. But I'm glad that 'eventually' wasn't today, because I love working with you and spending my time at the precinct and I know that as soon as Gates finds out, those days are over. I'm not ready for that.

Truthfully, I never will be. But as long as you're still coming home to me at night, I suppose I can learn to live with it. Even if I can't be your partner at the precinct, I'll still have you in my life and that's what matters most.

Love,

Rick

"You'll always have me," Kate murmured, tilting her chin to smile up at Castle.

He grinned, pressed his lips to hers. "Ditto."

She would always have his heart, and though it'd taken longer for her to open herself to it, he now knew he would always have hers as well.

"Birthday present or not," she added as an afterthought.

"Mmmm."

"Castle," Kate murmured, drawing him from his haze.

He allowed his eyes to flutter open to meet hers, deep and serious.

"You gave me this," she stated, lifting her left hand into their line of vision. "And this." She covered his chest with her palm, could feel the steady beat of his heart beneath her fingertips. "And those are the best presents I could ever ask for."

"But this was in September," he protested, catching her left hand and twining it with his. "And this," he covered her right hand that rested on his chest, "you've had for years now."

"I know," she agreed, well aware she was being a complete sap. "But that's all I need."

"So if I decorate your desk with flowers..." he faltered at her glare, knowing very well that his suggestion fell far outside the realm of 'keep your personal life out of the precinct.'

"Castle."

"Right, so if I make you breakfast in bed and shower you with roses and kisses and chocolates, you'd take it?"

Kate snorted. "What is this, Valentine's Day?"

"I, well, umm..."

She smiled. "You're sweet Castle."

"So that's a yes, then?"

"But you missed one very important part of my hypothetical birthday present," she cooed, an indirect answer to his question as she slithered off of his lap and made her way towards their bedroom.

Castle raised an eyebrow. "Oh yeah? What's that?"

Kate reached down, grasped the hemline of her shirt and pulled it over her head, exposing her bare back to him. She tossed her hair over her shoulder, turning only her head, a horrible tease. He gulped as she disappeared through the doorway, stepping out of her pants, leaving her clad only in what could barely be classified as underwear.

"You coming, Castle?" she called out, voice alluring and mixed with teasing overtones as she vanished into the shadows of the bedroom.

He swallowed hard, stumbled his way to his feet, fingers already working his belt and the button on his jeans as he followed her naked form into the darkened room.

"I sure hope so."

Author's Note: There is an outtake to this chapter as well, posted as chapter 2 of my fic 'Sweetest Words.'