I've been trying to update at least once every week.
I've had this written for weeks now.

September 18, 2065

He hadn't been expecting it to happen so quickly. He always knew it was going to happen, but even at 92, he always thought he'd have more time. With her.

He never imagined outliving her. She'd always been the healthier of the two.

It started when she woke up in the middle of the night panting. She told him she was fine. It was probably just a dream she didn't remember.

Then she would run out of breath as she walked from their bedroom to the kitchen. She told him she was fine. She was just getting older and he knew all about that, didn't he?

When he caught her hunched over the sink in their bathroom, clutching her chest, he took her to the hospital.

Heart failure, the doctor had said. When Rick argued that that wasn't possible, that she was more in shape than anyone he knew, that she had run until she retired and still did yoga every morning, the doctor had given him a sympathetic look and told him that sometimes these things just happen.

Sometimes hearts just… stop working.

It's a miracle, they told him, that she had survived this long with all the trauma her body had gone through: Explosions, hypothermia, bullets, torture…

A heart can only take so much.

They told them that she could get a transplant, but they had no human hearts available and she was far down the list, and the mechanical prototype would need to be ordered and shipped from California, and those were on backorder because of all the 40-somethings with money that wanted to live forever, and yes, the system was flawed but that's just the way it is.

Other than that, the doctors said, there's really nothing else they could do. They put her on medicine for the pain, and kept her in the hospital.

He called his children and told them what had happened, and they all came to say their goodbyes. Alexis and Ian had come by, Spencer and Riley coming later on the first day, Jonathon, Veronica, and James came by on the second, and on the third day the doctors said they didn't think she would make it through the night.

So when she told him she wanted to go home, that's what he did. He checked her out of the hospital, and took her home.

September 19, 2065

"Can we go to bed?" she asked him quietly, "I'm so tired."

When they had gotten home, he had asked her what she wanted to do. So they were in his office, he was sitting in his desk chair with Kate curled up on a chair right next to him. He was holding her hand, rubbing the long since wrinkled skin while he read her Heat Wave, the book that had started their lives together over 50 years ago. Real books had long since become obsolete, ebooks taking their place but his books still sat in the outdated bookshelves that separated his office from the rest of the loft, the two of them from the rest of the world.

He closed his eyes and took his reading glasses off, nodding at her.

"Of course we can."

He closed Heat Wave and set it on his desk, put his reading glasses on top of it and stood up, ignoring the creak of his aging bones. He held out his hand to her and she took it, and he led her into their bedroom like he had done so many times before, but this time much slower, as if he could prolong the inevitable.

Or maybe they just couldn't go any faster.

He helped her get changed into her pajamas and he put his on as well. He led her over to the bed, pulled down the bed sheets, waited for her to crawl onto the mattress that had been their haven for half a century before he covered her up and moved to his own side, slipping under the sheets to lie next to her.

As she settled up against him, she exhaled unsteadily.

"I'm so sorry," she said.

He squeezed his eyes shut, willing away the tears.

"None of this is your fault," he reassured her, "There's nothing to be sorry for."

She nodded against his chest, as if his apologies somehow made it all easier to deal with.

Maybe they did.

Anything to make it easier.

"All of our friends are already gone."

He didn't respond, but she kept talking.

"Esposito's been gone for almost 40 years…" she breathed, inhaling deeply once, trying to get as much air into her lungs as she could, "… and then Ryan and Jenny in that subway crash…. And Lanie a few years ago with her breast cancer..." she chuckled slightly, "You'd think by now they would've found a cure for cancer."

She inhaled again.

"I'm not scared," she said suddenly, her voice as strong as she could possibly make it, "I just don't want to leave you alone."

He pulled her tighter against his chest. One of his arthritic hands ran up and down her back slowly, and he could feel the ridges of her bones beneath her skin.

"I won't be alone," he assured her, "I'll have Alexis and Jonathon… and all of our grandkids. They'll take care of me."

"Well someone has to," she laughed lightly, but it sounded more like a wheeze.

He chucked with her, happy to be the butt of another joke if it made her happy right now. They laid together in silence for a long while and for a minute he thought that she may have fallen asleep.

"You're the greatest thing that's ever happened to me," Kate said a moment later, her voice even softer than before, "I don't think I told you that nearly as often as I should have."

"Hey," he said softly, his hands still running up and down her back, "No talking like that. I know, Kate. I know. I got to spend 50 years of my life with your ring on my finger and nothing is ever going to take away the happiness you've given me, or what we've given each other. I don't regret a thing."

Kate inhaled through her nose.

"I don't either."

His hands stopped rubbing up and down her spine and he held her tightly against him, feeling her chest rise and collapse against his side like he had nearly every night for over 50 years.

"Castle?" she whispered against his chest.

Wow, she hadn't called him that in years.

"Yes, Beckett?" He said back. He felt her smile through his shirt and he pressed a gentle kiss against her nearly white hair.

"I love you," she looked up at him.

He leaned down to meet her, kissing her softly.

"I love you, too," he smiled.

She smiled back at him before settling her cheek back against his heart. Her left hand, still wearing the wedding ring that he had put on that very finger 50 years ago, came up and settled itself flat against his sleep shirt.

"Always," she breathed against him. Her eyes slid shut.

He felt his heart clench in his chest and nodded. He could feel her breathing slowing against him and grabbed her hand on his chest in his own, squeezing it tightly. He leaned down to press another soft kiss against her hair.

"Always, Kate."

When he woke up in the morning, he clenched his eyes shut, willing the tears away as he clutched at her desperately.

She was gone.