A scene from “Secret Santa”

Rick Castle: You volunteered to take Eldin's shift. Don't pretend. If you aren't ready, why not just tell me?

Kate Beckett:I'm sorry, Castle. I didn't mean to...

Rick Castle:You didn't mean to what?

Kate Beckett: Christmas means something different to me than it does to you.

Rick Castle: It's Christmas. I mean, how can it be different?

Kate Beckett: Castle, every winter, as soon as that chill rolls in, I'm right back there in that alley. January 9th, and we still hadn't taken our Christmas decorations down. And by the time my dad and I did, it was like we were putting Christmas away forever. We haven't opened those boxes since.

Rick Castle: I didn't know.

Kate Beckett: That's why, every year, my dad goes up to his cabin. And ever since I became a rookie, I have taken the Christmas shift. Because I know that there are families out there that are celebrating together in their homes and I am keeping watch, and that is my tradition. And that is important to me. It's as important as your tradition is to you. And I'm sorry, Castle. I thought I could let that go, but I...

Rick Castle: I understand.