Based on a prompt from the castlefanficprompts page on tumblr:

In Knockout, Beckett is shot not in the chest, but in the back. The bullet damages her spine and she's paralyzed.

The loud thump from upstairs has him bolting from his office chair, taking the steps two at a time to reach the guest room at the end of the hall. It's almost three in the morning, but ever since her release from the hospital, he hasn't spent much time sleeping. He's too afraid, too terrified to sleep through something like this and leave her stranded without anyone but his resentful daughter to help her.

"Kate," he breathes, the only warning he offers as he pushes open the bedroom door. His heart breaks, just like it always does, when he finds her on the ground next to the side of the bed.

"Fuck, Castle, go away," she cries, slamming her fist into the carpeted floor, trying and failing to push up onto her elbows.

He ignores her frustrated demand and comes for her crumpled body, scooping her up from the floor even as she curses him through the tears clogging her throat and pouring from her eyes. She beats a hand against his chest, the blow weak and halfhearted, before she collapses against him, buries her face in his neck.

She was trying to reach her wheelchair, trying to transfer her body from the bed to the chair she despises with every fiber of her being, and she didn't make it. It isn't the first time it's happened, probably won't be the last.

"You're supposed to call me for help," he growls, squeezing her thigh, even though she likely can't feel it. "We've talked about this, Kate. We've talked about it so many damn times-"

"I just wanted to brush my teeth," she sobs, pathetic and miserable. Heartbreaking. "But the stupid chair - too far - I hate this, I hate it so much."

"I know, love," he sighs, rocking her in his arms even though he knows the action he too often indulges tends to make her feel coddled. She curls her arms around him this time though, trying to muffle her broken sobs against his skin.

It's been months since Montgomery's funeral, since the gunshot, since the damning diagnosis after she awoke from surgery. She still hasn't regained feeling below the waist and at their last visit with her doctor, she was told she likely never would.

"Don't call me love," she chokes out. "Don't love me, Castle. Don't-"

"Stop it," he growls against her temple. He hates when she gets like this, the self-loathing born from her paralysis convincing her she doesn't deserve him, that he doesn't deserve to be 'stuck' with her. But he didn't move her into his home, didn't stick by her through every grueling day of physical therapy, didn't rearrange his life, his loft, around her and her disability out of obligation. "I love you," he states, the reason for all of it. "I'll always love you."

Her fingers snag in the collar of his t-shirt and he rests his cheek against hers.

"Can we go to bed?" she rasps, her voice still cracking with anguish, and he nods, grateful for the request as he turns back towards the open doorway. She had only stayed in the guest room tonight out of stubbornness anyway, trying to prove something to herself, trying to will herself into believing she could take care of herself without any help.

He doesn't know how to make her see that she doesn't have to do this alone.

Rick catches a glimpse of red hair in the darkness of the hallway when he emerges from the guest room, notices his daughter's piercing eyes watching them from her cracked door. He's thankful Kate's eyes are closed against his neck, that she doesn't see Alexis studying them from her bedroom. The woman in his arms feels guilty enough for the rift between him and his daughter that she believes is all her fault.

But for once, Alexis doesn't scold him with a look of disapproval, doesn't make a passive aggressive remark about the situation, or glare at Kate when her back is turned. For once, Alexis gives him a small, tentative smile, and he wonders what she heard to evoke that.

His daughter disappears back into her bedroom without making a sound and Kate exhales an unsteady breath against his neck.

"I hope she can forgive me one day," she whispers and yeah, she's definitely still a detective.

"You have nothing to be sorry for, Kate," he murmurs. "But I think she's forgiven us both."

He braces her against his chest once they reach the stairs, making sure his grip on her is secure. He has a horrible fear of losing his balance when he's carrying her, of dropping her and causing her more pain. He wouldn't be able to forgive himself if he helped her attain yet another injury.

"Castle?"

"Hmm?"

"You know I love you," she breathes as they descend the stairs and he kisses her forehead once they reach the bottom.

"I know you do."

"I just want better for you."

He shakes his head.

He carries her through his office, stopping by his desk to close the lid of his laptop, and walks with her past the threshold of his bedroom. His arms are aching by the time he deposits her gently on the bed. He's built muscle in his upper body over the last three months and she's so light in his arms, too light, but his lack of sleep is catching up with him tonight.

"Kate," he starts as he crawls in beside her, helping her slide her legs beneath the sheets before drawing her up against his chest. "Stop trying to decide what's best for me."

She stays quiet at that, but slides her arm around his waist, slipping her hand beneath his shirt to splay across his lower back.

"There's nothing better than you," he says into her hair, tightening the arm around her shoulders when a quiet whimper escapes her throat. "I loved you when you could walk and I'll still love you if you never walk again. Will you ever believe that?"

Kate tilts her head upwards on the shared pillow, meeting his gaze with eyes that shimmer in the moonlit darkness of his bedroom. Castle smooths away one of the tears that escapes from the corner of her eye with his thumb and she spreads the fingers trapped between their chests to span over his heart with a sigh that trembles its way out of her throat.

"I'm - I'm getting there," she confesses. "I can get there, Castle. I will. Just - don't give up on me. Not yet."

"Not ever," he corrects, too quickly, too fierce, feeling his heartbeat picking up speed beneath her fingertips, but Kate only hugs him tighter with the arm still slung around his waist. "I'd never give up on you, Kate."

For the first time in a long time, he feels genuinely hopeful that they'll make it through this. Together.