A/N: This is based on a prompt I saw on tumblr in which Castle speaks to his unborn child every night from the first to last month of Kate's pregnancy. Pure fluff. Will have multiple chapters. Every view/favorite/follow/review is always appreciated. Enjoy! :)

Month 1

It is almost 3 a.m. when he slips into bed. He has been in here two hours ago, but the day's news have kept him awake, unable to even consider sleep. Kate is already asleep on her side of the bed, completely oblivious to his temporary absence.

Castle and Beckett talked and hugged and kissed until midnight when the exhaustion finally took over and pulled her into sleep. And he tried and tried, but after what felt like an eternity, he gave up on tossing and turning, trying to sleep, and instead moved into his office.

Writing usually calmed him down, gave him the possibility to process and deal with almost anything life threw his way. Tonight, however, he never managed to form a coherent sentence, his thoughts racing too quickly to put on paper.

So instead, he browsed the internet and watched funny YouTube clips. He tried occupying his mind, because he was sure sleep would never find him if he could not keep himself from thinking about today over and over and over again.

"I'm pregnant."

It's a phrase that replayed in his head constantly since he first heard it.

He felt his excitement rise again and could not suppress the giddiness that came along with it. They were going to have a baby. There was going to be a mini Castle or a mini Beckett running around. They were going to have a baby. A baby.

He got up from his desk, incapable of sitting any longer, and grabbed one of the books from the shelves. Maybe reading a crime novel would be a good idea. The grim mood might help him regain his composure. But after reading the same page for the fifth time, his brain refusing to focus, he gave up. He tossed the book on the couch he sat down on.

There was no way he could focus on anything else anytime soon.

After all his failed attempts to distract himself, he finally decided that there was no reason he couldn't just stay in bed with his wife, even if he was sleepless for the remainder of the night. Then at least he would not be wasting time, wouldn't be wasting a single precious minute that he could spend with the love of his life – and his future child.

He shifts and drapes an arm around Kate. She looks so peaceful in her sleep, and he feels himself overcome with a sense of gratitude at the sight of her.

Rick still doesn't feel tired. Frustrated, he turns on his back and stares at the ceiling. He lays there in silence for several minutes, before eventually letting out a sigh and beginning to whisper into the quiet bedroom.

"Hey there. I'm aware I'm kind of speaking to myself right now. I'd be writing if I could, but it seems like that isn't a possibility right now. So here I am talking. Words help me, even when they're not on paper," he begins.

He pauses for a moment and makes sure that his talking isn't waking Kate up.

"I only heard of your existence a few hours ago, but I already have so much that I want to tell you. And I figured, why not start now? How about I start with how you became the biggest surprise of the day? Definitely one of the biggest surprises in my life.

"Kate, your mom, and I, we'd considered the possibility. I just didn't expect it to happen so soon after… after everything that happened not that long ago. I'll tell you about that some other time," he murmurs, not sure if that is a story he will ever want to tell his child.

Remembering the horror in Alexis's eyes when she realized that her father was in mortal danger is something he doesn't want to relive. It still makes him shudder. But he is always trying to be honest with her, and he will continue to try with the new one as well.

Maybe one day, when their child is older, they can explain. But for now, Castle wants to focus on the happier moments of his life.

"I was out all day. Tons of meetings, a signing, running errands. I don't usually come home after Kate does, but today I did. I was really glad to see her after such a long day. I'm always happy to see her. Even when she's grumpy.

"She's been a bit silent and closed off. But she's like that sometimes. But she's also been grumpy a lot recently. That's unlike her, but I figured that work has been extra stressful, you know? Kate is the best detective ever. She's a Captain now, because she's so good at what she does. I visit when I can, I bring her coffee when I can to make her smile. And I work cases when I'm allowed to, just so she has less to worry about."

He falls silent momentarily, thinking back to the past two weeks. Now that Beckett is Captain, he couldn't shadow her quite as often, nor is she working in the field as much as she used to.

And as much as he loves just watching her, he still avoids doing so when she is doing paperwork.

Instead, he hung out with Ryan and Esposito a bit more. It wasn't the same as working with Beckett, but at least he continued having insight into cases. Castle had at least managed to help the boys with one case, his slightly obnoxious theory giving the two an idea for another possible suspect, who ultimately turned out to be the killer.

Kate was really pleased to see another case wrapped up. It temporarily lifted her mood, but for a reason neither Castle nor she could figure out, it quickly dropped soon after.

She seemed fine one minute, and then snapped at the people around her for no apparent reason.

It's so obvious now.

"When I came home today, she told me she'd been in the field today. She doesn't get to do that a whole lot anymore, but she misses it. But things weren't completely normal today. Apparently, when she saw the corpse, she threw up. That's unlike her too. I was really worried when she told me, until she gave me an explanation."

His mind drifts to the past evening when he'd returned from his day out and settled on his couch with her.

"You threw up?!"

"Castle, if you'd just listen for a minute, I can explain."

"Are you sick? Should we go see a doctor?"

She chuckled. "I already did."

His eyes widened in shock. "You already did?" he asked. "So it's serious? What's wrong? Kate, please just tell me."

She sat up straight. "I was worried too, you know. I've been so moody recently, and I never throw up, especially not because of a murder victim, but I just felt so weird."

"So what is it?" Rick pushed, eager to understand.

"I described all my symptoms and everything that's been weird lately. I think, deep down, I already had my suspicions, but it seemed too absurd. Given that I'm a detective, it's almost stupid I didn't figure it out sooner," she laughs.

"What is it?" he asked again impatiently.

He could see Kate's eyes glistening, which only caused him to worry more. He took her hands into his, searching for her gaze. When her eyes met his, she smiled.

"I'm pregnant."

It was a simple statement, direct, and yet he found that he stared at her in disbelief.

He was motionless for a moment. And then, he understood, and tears he hadn't noticed welling up were rolling down his cheeks.

"I think I cried more than she did," he admits quietly. "Part of me thought she was playing a prank on me at first. But she showed me the test and the doctor has apparently confirmed it. I didn't think I could love her more, but I do. I'm so happy."

He takes a breath as he feels water stinging in his eyes once again.

"We haven't told anyone yet," he whispers. "You'll be our little secret for a little while longer. Not too long though. Kate and I once tried to hide our relationship, and we were pretty bad at that too. My mother knew from day one, I told my daughter about it not soon after… Ryan almost made a suspect cry to find out who I was dating."

He almost laughs out loud at the image of Ryan interrogating their suspect from the Hamptons.

When Castle first heard that someone who could possibly reveal their relationship had been interrogated by Ryan, he was so scared that their secret had been uncovered and that their partnership would end as soon as word made it to Captain Gates.

Now, however, he finds the idea of the detective pushing Lerner to discover his girlfriend's identity pretty amusing. He actually laughed out loud when Ryan told the story to him several months later.

"And then, I managed to get myself into trouble – I do that a lot, you'll get used to it – so eventually, Esposito and Lanie found out as well. So I think it's safe to say that you won't be our secret for very long. Stuff like that happens when you're constantly surrounded by great detectives... or a mother who likes sticking her nose into other people's business."

"I'm so happy," he repeats. "And I'm so happy to see how excited Kate is too. There weren't a lot of reasons for us to smile during the past year. Now we have a reason, and it's enough to make me think that my face might stay in this position if I continue. Smiling so much actually kinda hurts."

He smiles as he says it.

But after everything that happened last year, all the battles they fought, hurting from smiling too much isn't the kind of pain he minds.

"I would appreciate, however, if I could while I sleep. I fear that you'll keep us on our feet enough when I can physically hold you, and I'd like to be able to rest before that day comes," he jokes.

He yawns, his monologue having succeeded in helping him process the day's events. He feels like this won't be the last time he'll be talking to his unborn child.

It takes a while, but eventually, he is able to drift into sleep, his peaceful expression matching Kate's.