A/N – A short one-shot post 47-seconds. Set three days after Castle hears Beckett in that interrogation scene. He hasn't spoken with her for 3 days. For the sake of this short, assume that Castle never hid his conversation with Mr. Smith, and instead told her the truth. Makes it a little AU, I guess, but it works out better that way.

I could probably expand this, if it is popular enough, to include Kate's reaction.

Thanks in advance for any reviews or favs! They are love.

He couldn't not say goodbye. He had been with her for four years already, and she at least needed to know why he was leaving, why he couldn't bear to be in her presence any longer, why he wouldn't be there for always. But he couldn't talk to her. It'd be too painful, to unbearably painful. He was a coward. Just like her.

So he wrote a letter. His words had always been his tool for expressing himself, so this time they couldn't fail him. He had to let her know.

Dear Kate,

You have probably wondered where I've been these last three days. I know you've tried to call, and even tried to see me at home. I'm an ass for doing it this way, but you need to know what's going on, and why I can't be there.

I know you lied about that day in the cemetery. I overheard you talking to one of the bombing suspect a few days ago. I can never un-hear what you said.

I love you, Kate Beckett. More than life itself. I would have died for you in that cemetery a few months ago. I would do anything to spare you pain; you've suffered so much in your life, and I don't want to add to it.

But at a certain point, I need to think of myself. I can no longer be your partner. I kills me to write that sentence, but I can no longer stay by your side when I love you so much, and it's obvious that you don't feel the same. After all, why else would you lie?

I know my declaration of love didn't come at the best time, and that thrusting that upon you when you were fighting for your life wasn't something that should've been done. I know that when you woke up in that hospital room that you were feeling overwhelmed, and that you might not have known how to deal with what I said. I know all that. But we trust each other, Kate. With our lives, every single day. And you've broken that trust.

I would have waited forever if need be. All you needed to tell me was that you needed time, or you could have told me that you didn't love me. Either way, we'd still be able to work together. I'm a big boy. I can handle the truth. But I can't handle the lie.

Love means the ability to forgive someone their sins. I do forgive you for this Kate. It isn't your fault that I fell in love with you. It isn't your fault that you don't feel the same way. Even the lie on that day in the hospital isn't unforgivable. But I cannot stick around knowing what I know now.

This is going to kill me, Kate, that's for sure. I promised you ALWAYS, and I tried every single day to make it apparent to you that I meant that. It's a promise I'm going to have to break, for my own sanity, and that more than anything is breaking my heart.

You should know that I will always love you, and that I will never get over you. You were the one. You were it for me. And even though our chance is gone, I will always love you.

I hope that someday you can find happiness. I hope you find someone who can be there for you and you can be there for him; someone you can just dive into it with. I hope that you find what you are looking for one day. You deserve so much in life, Kate. I hope you find it.

Love Always,

Rick Castle

Castle printed the letter out on his ink-jet printer that sat beside his desk, placed the letter into an envelope and wrote the initials KB on the front after sealing it. He was done.