A/N: Still completely overwhelmed by the amazing response to this story! So glad that the majority of you are enjoying it! If you're reviewing as a guest with concerns for why I'm writing things a certain way, you'll never know the answer if you don't give me an option to reply. Regardless, I'm going to continue writing the story I want to write. If the words cooperate the next chapter will be switching to Castle's POV for the remainder of the letters.

Disclaimer: I do not own Castle or any of its characters. Kudos to the real Castle writers, I love the story they continue to write for us.

My Mentor

"The most difficult aspect of moving on

Is accepting that the other person already did."

-Faraaz Kazi

The third day of packing turns out to be the hardest. She thought that if she kept herself busy she wouldn't dwell on wondering if Castle had read her first two letters. She was wrong. It turns out that each part of her apartment that she tries to pack reminds her of him. She learned in the beginning that he likes to touch things, his curiousness being one of the things she's grown to love about him. He's touched almost everything she picks up. She knows because she remembers the conversations they had about the different knickknacks and decorations that adorn her apartment.

It's not just the items she's packing that remind her of him. Their sex life has been adventurous, to say the least, and she remembers—in detail—each area of her apartment that they've christened with their love. It's safe to say that they've utilized each and every surface and structure. In other words, trying to keep her mind off of Castle is a battle she's losing.

She starts packing her closet sometime around noon, carefully stacking her numerous pairs of shoes into boxes, only leaving out the few pairs she needs for the rest of the week. There's a part of it that she's carefully avoiding, a small corner that he's claimed, and even when she's on the other side of the closet, his scent fills her nose, wrapping her senses with him so much that her heart aches more than ever.

She can't avoid packing the closet forever though, there aren't that many days left in the week. Her lease isn't up for several more months, so she doesn't have to do anything with his things right now. She's hoping she won't have to do anything with them at all.

She's half-way through sorting her hanging clothes when she spots a small black box on the top shelf of her walk-in closet. She reaches for the box, carefully pulling it down and walking out of the closet to sit on the bed.

She remembers most of the contents in the box, little things that mean something to her that she's collected over the years. However, as she pulls a few things out, one item in particular catches her eye. With careful fingers she lifts the folded paper out of the box, carefully unfolding it and reading over words that she's already memorized, words that are forever etched into her mind.

It's remembering the last few words of the letter she's holding, scanning over them for the millionth time, that has her reaching for the now familiar pad of paper and pen that she left on her nightstand. Castle already has two letters from her, and she's still not sure if he'll read them, but the pen in her hand is already moving over the paper, and the third letter begins to take form.

Castle,

I've sent you two letters so far. And they aren't just normal letters because you know by now that words are not something I give easily. The words I'm writing to you are straight from my heart, words that I've never given you, but that you deserve to hear. I haven't heard from you since our fight. No texts, no calls, no contact at all. At the moment, I don't know if that's good or bad.

Since I've already started this—committed to sending you my words, I intend to keep going until they stop pouring out of me. If you've read the two that I've already sent you, you now know more about me than—well, more than anyone. The truth is, everything I've written to you, everything you've hopefully read, it's more than just words. These are thoughts that I've never voiced aloud, never let wash through me, never shared—or wanted to share—with anyone. Until now.

So many times over these past few weeks, I've picked up my phone to call you. I've let my finger hover over your name for what seemed like hours before I put my phone down and walked away. This is not something I would admit to just anyone, but I'm desperate to hear your voice. I miss you, Castle.

By now, assuming that you've read the other letters, you should know the general theme of them. As much as these are for you, they're for me too. I never realized how therapeutic writing could be, although, I'm not sure if it's the actual writing or the fact that I'm writing to you. Maybe it's both.

Today, as I was looking through a box of old things, I came across a letter that was given to me during a case. It was a case we worked together. In fact, it's one that I'm sure you'll remember quite well. The letter is from Royce. CSU found it on him at the crime scene and handed it over to me before we left for L.A. I didn't read it all the way through until we were on the plane on our way home.

Mike Royce was many things to me. He was my training officer and first real partner. But more importantly than either of those, he was my mentor. I've mentioned before that he was the first person who understood the obsession that drove me. When I first got out of the academy I spent as much of my day as I could get away with poring over my mother's case file. Royce never said a word to me. He would just give me this look that said 'I understand what you're doing, kid and I'm not going to stop you.'

His demeanor towards me and his ability to relate to my struggle are two of the main reasons that I fell in love with him. I'd never been in love before, not like the type of love I felt for Royce. But he didn't love me, at least not in the way I wanted him to, and that was the first time that I had to let go of him.

Maybe it's ironic that he rejected my love. A little bit of a lesson that I was never meant to grasp until I did a similar thing to you. The only defense I have against that is that I do love you, Castle. Even back when you thought it was a lost cause, you'd already consumed so much of my heart. I just didn't know how to act on it back then. I would have done nothing but push you away, you know that already because even without any type of romantic relationship between us, pushing you away is exactly what I did.

The second time I let go of Royce was when he left the force. He'd been with me in those first years, supporting and guiding me, and I wasn't ready to give that up. The first couple of weeks without him I wandered around the precinct like a lost puppy. Letting go the second time was even harder than the first.

When I had to arrest him, those feelings stirred back to life. I'm sure I never fooled you—I never could anyway—when I claimed that my love for him was just a bluff, a mechanism to get him to listen. All that really matters now is that it worked. That case took a toll on me because it made me question everything I'd ever really thought about him. After we closed it, I struggled to let go of him again. But this time I wasn't letting go of my love for him, I was letting go of who I thought he was.

His murder was the hardest of them all. You know more about it than anyone because even when I tried to do things on my own, you showed up. I don't think I've ever told you how truly thankful I am that you were with me through all of it. Seeing Royce's lifeless body was almost as hard as seeing my mom's. I managed to put on a pretty good front, but that case rocked me to the very core.

The only way I knew I was going to get closure was to find the man who murdered him. And while that was a big part of it, catching Ganz wasn't the thing that gave me the closure I needed. This brings me to the letter I mentioned in the beginning.

The final time that I let go of Royce was after reading the words he wrote to me. He only spent a minimal amount of time with you and I and still, he knew. He saw what was there all along—our connection. Even when we were still denying it, Royce saw it. In the letter he told me that I shouldn't wait, that risking our hearts is why we're alive. He was right, Castle. I realize that now more than ever.

When I finished reading his letter on the plane, I carefully folded it and when I got home I placed it in this box. I've re-read it many times since then, so much so that it's worn and tearing in some places. I think I could actually recite it without ever looking at it. Royce was a huge part of my life, an even bigger part of who I am as a cop. Letting go of him meant letting go of a part of myself. I had to accept the fact that I no longer needed his mentoring, that I was strong enough to carry on without him.

I did love Royce, and there was a time when I thought he was exactly what I wanted. But there's a difference between loving and actually being in love with someone. There is only one person that I have ever been in love with—that I am in love with. It's you, Castle—it's always been you, and there will never be anyone but you.

Letting go of three very important people in my life was hard. Each one took a toll on me that I had trouble overcoming. But each struggle has shaped me, molded me into who I am. It's what continues to propel me forward even when the pain tries to hold me back.

I have the letter here, in this box. It's fragile and worn, much like the hold that I had on Royce, but it's here. I want to share it with you, just like every other part of my life.

Castle, I don't want to continue living without taking the advice that Royce gave me. If risking my heart is why I'm alive, then I want to risk it—on you.

-Always, Kate.

She places Royce's letter back in the black box and closes it before placing it into a packing box that's beside her bed. She folds her letter to Castle with the same carefulness and slides it into the envelope.

She drops it in the mail that evening on her way back from having dinner with her dad. As she places her key in her mailbox she holds her breath until the little door swings open and her mail is in her hand. She doesn't stop to look through it until she's back in her apartment.

Leaning against the door after she closes it, Kate sifts through the mail, her normally steady hands shaking slightly. As she scans over the last piece in her hand she lets out a relieved sigh.

They aren't there. He didn't send them back to her.

By tomorrow afternoon he will have three letters from her, three different pieces of her heart that she's willingly sharing with him, parts of her that no one else has ever or will ever know. The letters don't change the mistake that she made. They don't fix the damage that she's done to their relationship. But if writing the words of her heart to him helps to heal her, if it puts her broken pieces slowly back together, maybe they have a chance. If anyone can take her brokenness and make it whole again, overlooking the small cracks and imperfections that remain, it's Castle.

She wants him to be her future, but the only way that can happen, is if they overcome her past.

Thank you to Bri for the beta and continuous pep talks when I hit a wall with writing. Xoxo

Would love to hear your thoughts! xo