Author's note: I was at a wedding this weekend... and this idea just flooded me. It takes place in the far off future, and there is a ton of implied "backstory" (as in, stuff that would have happened after season one, but before this fic). I hope I've left enough clues for you to fill in what happened. I'm REALLY unsure about this fic, so PLEASE leave me honest feedback so I know how I did! The lyrics I used are from Scott Clifton's "Bitter" and Michal Towber's "Ripe." The title is from The Librarian, a movie Stana Katic was in.

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"I, Richard, take you Katherine... I, Richard, take you, Katherine..."

He stood before the full-length mirror, skull-white and a tremor at every limb. His palms sweat as he struggled to secure his tie in a manner befitting the formal demands of the ceremonious occasion he could feel rumbling the ceiling beneath his feet. He just couldn't bring himself to smile.

"Nervous?"

Just over his ear in the mirror, he saw his daughter approaching. She patted his shoulders and smoothed the creases down his sleeves, dusting off a wayward piece of lint here or there. He sighed and addressed her reflection. "I don't think I can do this."

Alexis faltered. "What? Dad. You have to."

"No I don't," he said stubbornly, turning around to face her. "Everything's changing. If I go down there now, if I face what's waiting for me down that aisle, I'll be allowing everything to change. But maybe if I just stay here and hide my head between my legs, then the wedding won't happen and everything can just go back to the way it was. The way it used to be."

"Dad, you know you can't do that," Alexis said wisely.

"You have no idea," he said quietly – not accusatorily, just regrettably. "I can't tell you how difficult this is for me, what it means for me to strap on a suit and go down there and do this."

"I know," she said. "But you can't back out now. If you do, you'll only make things worse. You've already made the promise to her," she pointed out. "Now it's time to make the commitment."

Castle sighed, pulling his daughter into a hug. It was the kind of hug that a father might give his daughter to comfort her, but this time, she was the one providing all the comfort. "How come you're so smart?"

She laughed into his lapels. "Years of experience."

"I mean it, kiddo. Thanks for the pep talk."

"Don't sweat it, Dad," she said, pulling back to look up at her father. "I'd never forgive myself if I let you screw this up."

He tousled her hair playfully and worked up the courage to smile, just briefly, before inhaling fully and heading downstairs. He maneuvered stiffly through a crowd of strange faces, feeling ghostly and hardly aware of his feet. His breath hitched on exhale when he saw her father.

"Mr. Beckett?"

"Ricky," he sang on a low note, grabbing Castle's right hand with both of his and shaking it confidently. "Good to see you again, son."

Castle winced but morphed it quickly into a smile. "How are you, sir?"

"Doing pretty good. My little girl's getting married," he answered with a proud laugh. "Hard to believe, isn't it?"

"You can certainly say that again," Castle confirmed.

"Oh, just wait till you see my daughter in her wedding dress," Mr. Beckett boasted. "She looks like a royal queen with the beautiful grace of an angel."

"I'm sure she does, sir."

"I only... wish her mother could have been here," he said, suddenly looking very tired and very old. Castle's heart pounded ferociously through his three-piece suit.

"You had no right, Castle, no right whatsoever!"

"Sweetie, I was only trying to help you."

"No, you were only trying to help yourself!"

"You know that's not true."

"Tell me, was it worth it? Huh? Was it worth it to humiliate me and decimate my mother's memory, all so you could sell another book?"

Castle shook his head, the voices fleeing like dying wind. He clapped a sympathetic hand to the man's shoulder and made his silent way into the wedding hall. Spotting Ryan and Esposito sitting together in a pew near the back, he shuffled in next to them.

"Hey!" Ryan whispered cheerfully. The two detectives took turns clapping hands with Castle in brisk handshakes. "Great to see you, man, how you been?"

"Oh, you know, living out the end of my success," he said with a sad smile.

"The end?" Esposito asked.

"Yeah, well, since I wrapped up Nikki Heat a few years ago... I haven't written much."

"Early retirement?" Ryan guessed.

"Doesn't feel early to me," Castle said cleverly.

"Ah, well good for you," Ryan said genuinely. "Esposito and I'll be working dead bodies till we drop."

"I don't envy you," Castle conceded. "What you do is not pretty."

"Eh, somebody's gotta do it," Esposito said with a shrug. Castle suddenly became acutely aware of how trite and formal their conversation was, making him uncomfortably disheartened. Here he was, sitting with two old friends who used to be such a huge part of his life, and now they were all making such superficial small talk. It made Castle regret more than ever letting it all go. He sat quietly while the other two made sporadic comments to each other about one thing or another until the lights dimmed, the room quieted, and the music began.

Castle didn't recognize anyone who came down the aisle until he saw Lanie, presumably the maid of honor. When the music shifted gears to the obvious wedding procession, everyone rose and faced the door. Castle was the only one who hesitated and, fortunately, the only one who noticed. Through the doorway stepped a beaming Kate Beckett on her daddy's arm.

Mr. Beckett had not exaggerated her beauty. Even given a thousand pages, Castle had to admit even he could not have described her justly. She noticed him in the audience, but they were both careful not to make eye contact as she marched decidedly forward. When she reached the end of the aisle, her father placed a gentle kiss on her forehead and put her hands into those of the man she was about to marry.

Castle was the last one to sit.

"What a marvelous occasion," the officiator began with open arms, "to bring together Alex and Kate in the sacred bond of marriage."

Castle sat in heartbroken silence as the ceremony went through all the stages. With every word, he watched pieces of his past evaporate before his eyes. With every sniffle of joy that came from the audience, he felt the need to burst out screaming and run through the Tudor arches, but he sat very still and watched powerlessly as someone else shared smiles with the woman who once had his heart.

"I'm not an if-at-first-you-don't-succeed kind of a girl, Castle. When it comes to marriage, I'm more of a one-and-done type."

"Hmm. Any serious candidates?"

"Kate," Alex began when it was time for their vows, "it is with unspeakable joy that I put this ring on your finger today. You are the words of my poetry, the melody of my songs, and the spark of light that brings me home."

Ryan snorted quietly from the back row. "What a piece of work."

"For the last few years," Alex continued, "the happiest I've felt has been when in your company, and if I could, I'd like to return the favor, every day, until the last dying ember of our mortal lives extinguishes into the darkness of our eternal lives together."

Ryan and Esposito shared eye rolls while Castle ground his back teeth against each other.

"Alex," Kate said, "your words are more beautiful than those of anyone I've ever known." Castle closed his eyes, her words stinging more tartly than he would ever admit. "That night we met on the train... I was such a mess. I mean, anyone who knows me knows I've always been kind of a loner, but that night... I'd never felt so alone in my life. And there you were. I truly believe that, if it weren't for you, I would have died in the wreck that night. Not only did you pull me from the debris, but you gave me a reason to hope, a reason to live, all those months I was recovering in the hospital. Without you, I would have just given up. But you convinced me I was worth fighting for. You were worth fighting for. You give me courage, you make me feel beautiful, and what's most important, you make me feel loved. I will never forget all that you've done for me, and I can't wait to spend the rest of my life with you."

Castle opened his eyes when he felt Esposito's hand on his shoulder. He looked up and saw his old friend giving him his best attempt at a comforting smile. Castle shook his head and returned his gaze to the happy couple up front, just in time to see them exchange rings. His eyes stung and his throat burned, but he lacked the courage to cry. He felt too broken and every ounce of him was wholly focused on forcing himself to watch.

The crowd erupted with applause and cheers as the officiator pronounced them man and wife.

How dare you say you know my heart?

You've no idea just how this emptiness grows

Castle wanted to make a quiet exit in all the commotion. He'd kept his promise – he'd shown up. He certainly didn't want to join everyone for the celebration of the new Mr. and Mrs.

When he felt three fingertips at his elbow, he knew his chance to escape was gone. Only one person ever touched him like that.

"Rick?"

He stuffed his hands determinedly in his pockets. There needed to be no chance for a handshake or hug because as soon as he turned around, every nerve in his body was burning to hold her. "Congratulations."

"Thank you. I'm really glad you came."

Castle nodded. He couldn't say the same. "It's been so long."

"It's crazy, right?" she asked, looking everywhere but into his eyes. "I can't believe this is all happening."

"Kate..." His tone grabbed her attention, and she dared to finally meet his eyes. "Look, can I ask you something?" He paused, waiting for her permission, but she merely let go of the smile she'd been wearing all evening. He sighed, and swallowed hard. "Do you ever think about us? Think that maybe this could have been us?"

"Rick, don't do this..."

"No, I need to know," he pressed on. "If I'm going to make any kind of peace with this, I need you to do this for me."

Love ain't pain, it shouldn't be a game

Shouldn't feel like a wasted day

Shouldn't be so bitter

"Rick," she said kindly, and he could tell by her tone that her words weren't going to soothe him. "That was a long time ago, and both of us are living completely different lives now."

"If I had known," he said desperately, "if I could have known, you know I would have been on that train."

"I know. But you weren't."

"You have to know, I never wanted –"

"We've been over this," she interrupted. "You know I don't hold any anger towards you for that anymore, okay? I've let all that go."

"No, you haven't," Castle muttered. "Come on, Katie, you're too real to lie to yourself. I'm an author, remember? I've written this scene a hundred times. You just want everything to be okay, so you're feeding me these pretty little words so that when you go to bed with him every night, I'll have some microscopic consolation!"

"Rick, stop. That's not fair."

"Fair?" Rick whispered angrily. "None of this is fair, Katie. Fair would have been me putting that ring on your finger, not him, and you know it."

He turned to walk away, just hoping she would let him; it would have made things so much easier. But he knew she never would. That's just not how they were. "Wait," she called. "Come on, you're not even going to say goodbye?"

"You already did," he muttered without even turning to face her. "You said goodbye six years ago when you got on that train."

Somehow

It's getting clearer now

I'll forever be the man

I'll forever be the man you don't want