One-shot.

"It happened, Kate."

"What happened, Castle? What's wrong?"

"She left. I didn't think it would be tonight. I thought i had more time to convince her... I feel like she's throwing her life away, or at least opening herself to a world of hurt."

"Ok, Castle, I... I'm sorry. I have to go."

"But, Kate - "

"I'm sure everything will be ok, Castle. See ya.'

See ya?! See ya?! Shocked that his fiancee' would have such little regard for his emotional well-being, and just hang up on him like that, Castle went to bed fully clothed, not even bothering to take his shoes off as he crawled up into a ball on top of the covers, feeling sorry for himself.

He heard someone coming in through the front door about half an hour later and assumed it was his mother coming home from the studio; but then his bedroom door opened and he felt a warm body that most definitely did not belong to his mother curling up beside him and burying her face into his neck.

"Kate?"

"Mmm."

"You're here," he said.

"Where else would I be?" She asked

"I thought you wanted your space," Castle said.

"Yeah, back when the loft was grand central station," Beckett said. "But..."

"It's not any more," Castle finished for her, his voice cracking with emotion. "Because my daughter moved out with her boyfriend."

"She didn't really live here any more, Castle."

"It was still her home. Not any more, apparently." Castle couldn't suppress the bitterness from seeping through in his voice.

She stroked his hair.
"Oh, Castle. I'm so sorry."

They lay in contemplative silence or a few moments.

"Kate?"

"Yeah."

"What would you do if you could go back in time?" he asked her. "You know, hypothetically, if time-travel were possible, which of course it isn't."

"Well, I don't know about that, Castle. Apparently it is possible, according to physicists, but unless a time machine's already secretly been invented, it would be impossible for someone from the future to travel to this time."

"Talking about time travel with such authority while I'm in a vulnerable state... you wouldn't take advantage of me, would you, Detective Beckett?"

"Only if you asked me to," Beckett said.

He smiled.
"I think I'll wait for your answer first."

"Well... hypothetically, if Doyle was telling the truth, which... of course he wasn't," she said, trying to convince herself more than Castle, "I... would probably try to save my Mom."

He nodded.

"But I... honestly, Castle, I don't know how I'd do that. Would I go back and warn her? Would I try to stop Montgomery, Raglan and McCallister from kidnapping those mobsters, or just stop Montgomery from pulling the trigger? Would I try to stop Bracken from working for the DA's office? Just thinking about it hurts my head. It took me years to come to peace with my mothers' death, to reach a place where I could be happy... I don't know if I could bring myself to go back there. I mean, if I could snap my fingers and have my Mom be alive, I'd do it in a heartbeat, of course.
"Maybe, if it was possible I'd just... I'd do what you'd do. I'd relive every moment, knowing how precious it was, just being able to appreciate her more than I ever did the first time around. Even if I could talk to my Mom one more time, that would be enough for me."

He kissed her head.
"I think if I could go back in time, I'd change one thing: I'd make it so we could be apart of each others' lives sooner, so I could be there for you when your Mom passed away."

She smiled.
"Oh, Castle. That's very sweet. But you were there for me. In a way." It was the closest she would ever come to admitting just how much his books had meant to her.

He didn't push for more, instead caressing her wrist with his thumb.

"I wish you could have met her, Castle."

"Me, too. Do you think she would have liked me?"

She paused.

"Kate?"

"Well, Castle, remember, you're ten years older than me. You had a six-year-old daughter at that time. And you weren't exactly... serious, were you?"

"I'm still not," Castle said.

"You don't have to tell me. That's one of the things I love most about you, even when it drives me crazy. You know what? I think Mom would have liked you a lot as a friend. She would have found you funny and charming, smart and endearing. As a guy dating her daughter? Probably not so much."

Castle nodded.
"Well, I guess I can relate to that. Pi kind of reminds me of a couple of buddies I had in college. But the idea of one of those guys and my daughter..." He cringed.

"I think you would grow on her," she said, thinking about it. "Like you grew on me."

"So, what you're saying is... I'm a parasitic fungus which has infected your heart," Caste said in conclusion.

"Yeah. That's exactly what you should take from that, Castle.'

He nodded and sighed..

"Kate... when you moved in with that guy, was it before your Mom's death or after?"

"After," she replied. "Just after. Before I decided to switch majors from pre-law to Criminology, I was... lost. Without my Mom... I didn't know what I was going to do for the next day, let alone the rest of my life. I was dating this guy, Mark, nothing serious. He had his own place, so I took a little time off college and stayed with him for a while. He was the only person who wasn't constantly asking how I was, if I was ok... who just gave me the space I needed. And when I needed a little more, he was there for that too. Dad went ballistic, as fathers do. He wanted me to come home and I... I thought he was trying to control me, to help me, and I didn't want his help. I wanted to work things out on my own. What I didn't realise at the time was that... he wanted me home for himself, not me. Because he wasn't coping."

"But you did realise eventually."

"Yeah. Yeah, long after that relationship was over, after I'd decided to become a cop, gone back to Stanford, I found out my Dad was self-medicating with alcohol. It took a long time to get him on the road to recovery, and even longer for him to get himself to stay there. He would get on the wagon then fall off then get back on again; but I never gave up on him. Don't ever underestimate a daughter's love for her father, Castle."

Castle turned to face her.

"Kate, thank you for being here."

She stroked his cheek with her thumb.
"Always, Writer Monkey. Always."