Author's note: So this is my first Castle non-collab fanfiction. 6x 17 Post-ep of Castle's reaction to Kate's letter

It had been four hours since they had stumbled into the apartment early in the morning, and only three since he had convinced her to come to bed. He lay down with her with her head on his chest and his arms wrapped securely around her, enveloping her in his warmth. She had crashed out into a deep sleep almost immediately, the exhaustion of the past twenty-four hours hitting her hard. She had not broken down yet, had remained stoic throughout her recount of what had happened to her and the ride back to the loft, the only sign of it; the haunting in her eyes. He was not quite sure it had sunken in that it was over and that she was safe. But for now, he was sure that the exhaustion would keep the nightmares at bay, at least for the time being.

He stayed with her for a few minutes, watching her in her sleep before slowly extracting himself from her embrace.

He hated to leave her alone, dreaded the thought of letting her out of his sight, but the vivid images of her story, the haunted look in her eyes, the what-ifs, they flashed behind his eyes every time he tried to close them. He was exhausted but they would not leave him alone and there was no way he was going to wake her up with his own nightmares. His, he knew, would not be kept away.

So that is why he is now sitting alone on the couch in his office, Keeping Kate within earshot staring blankly at the rows of bookshelves with a cup of coffee in his hands that has long since cooled when the knock on the door comes.

He shuffles slowly to the door and opens it.

"Hey, man." Ryan says nervously shifting his weight from one foot to the other. "I know you guys are exhausted and are trying to recuperate but CSU found this while searching the house and I thought that it was better that I give it to you." He reaches into his pocket and pulls out a folded piece of paper with his name written on it in in what he recognizes as Kate's handwriting. "I thought you should have it as soon as possible." He gives him a knowing look.

Castle reaches out and takes it, a look of confusion and fear crossing his face before she quickly schools it and gives the detective his thanks

"Of course," he says. They stand there for a moment in an uncomfortable silence. What do you say after a day like today "Anyways, I'll let you guys get some rest." He rushes, "And…give Beckett a hug for me, okay?"

Castle smiles "Of course, thanks, Ryan." He reaches out to shake the detective's hand. "Really, for everything"

The detective simply nods before Castle closes the door. He stares at the piece of paper in his hand, almost certain of what's inside and it makes his heart sink.

He slowly makes his way back to the couch and sinks down onto the cushions. He thinks for a second that maybe he should wait for Kate before he reads it. But he doesn't want her to see the reaction he knows he is going to have to her words, not when she has been through so much already. He does not want her to see him break down when he is supposed to be her strength.

He almost doesn't want to read it at all and has to fight the urge to take a match to it and burn it, let the past be the past. But he knows he cannot do that. Both the writer in him and the part of him that loves Kate so deeply will not let him. He has to know. He has to know what she thought would be her last words to him, to know what it is she was thinking. He just has to know.

He takes a deep breath and slowly unfolds the letter. His eyes scan across the letter, slowly absorbing her words. It hits him like a punch in the stomach. No amount of expectation could prepare him for her words. Such beautiful words. She had said goodbye to him. She was scared an alone and though she was about to die so she took the time to write to him to say goodbye. And he had failed to save her.

The realization was a stab in the heart. He reads the words over and over again as tears slide unbidden down his cheeks.

I want to you to know that our partnership, our relationship was the best thing that has ever happened to me. You're an amazing man and I love you with all my heart. Always

Oh, Kate.

He has to physically fight the urge to go wake her up, to drag her into his arms and just hold her. Instead he grabs a pillow off of the couch and crushes it into his chest, burying his face into it, the letter left abandoned on the floor by his feet.

He takes deep, gasping breaths, attempting to calm the panic that is building in his chest. But everything he had been holding back since the moment he found out she was missing, the fear that came with every moment that he failed to save her, came bubbling up until a strangled sob broke free.

And then he broke down.

She woke with a start to darkness. She was not really sure of what woke her until she felt the absence beside her. The coldness of the sheets told her he had been absent for a while. She frowned in confusion. A shudder ran down her spine as the memories of the day before filtered their way back into her mind and suddenly she could not take the dark loneliness. She slowly rose from the bed to seek out her partner, wondering what had caused him to rouse in the first place.

She had just stopped to look in his office when she heard the muffled noises coming from the living room. She stepped out of the office and stopped dead in her tracks.

Castle was sitting hunched over on the couch, face buried in a pillow. His shoulders were shaking and she could hear the muffled sobs through the pillow. Then she spotted the creased piece of paper by his feet and she recognized it instantly. Her heart sank.

Oh, no, Oh Castle.

She moved carefully over to him and sank down next to him. She felt him stiffen next to her. She carefully tugged the pillow out of his grip and did not give him any time to react before she wrapped her arms around his neck and pulled him into an embrace. He fisted his hands into the back of her t-shirt and buried his face in her shoulder. She could feel the warm wetness of his tears soaking into her shirt and her heart broke for him. She had not realized how much of a toll that yesterday had taken on him and she mentally berates herself for it. He had been so strong and supportive of her since she was rescued it had not even crossed her mind. She guessed it was time to fix that.

She cradled his head with her hands, running her fingers through the short soft strands of his hair on the nape of his neck in a way that she knew soothed him.

"Shh, it's okay, Castle." She whispered, "I'm right here, it's okay." She whispered it over and over again like a mantra, running her hands through his hair and down his back until his sobs became less desperate and his breaths became less erratic.

They stayed like that until Castle slowly pulled back, resting his forehead against hers. He took a few deep breaths before he opened his eyes to meet her worried gaze.

"I'm sorry", he rasped. "You're the one who went through – through hell yesterday. I should be stronger for you, I-"

"Shh, no, Castle, no. Don't apologize for hurting" She brings up a hand to cradle his jaw, her thumb, swiping at the dark circles under his eyes. He squeezes them shut and shakes his head, another tear slipping out and running down his cheek. "Hey," she says, and she waits for him to meet her gaze. "You have been so strong for me already. But you were afraid yesterday too, you have every right to need comfort too."

"No, you don't understand, Kate," he says, pushing her away, distancing himself from her. "You don't understand," He said more softly. "I failed. You needed me to find you and I failed. You were so scared that you were going to… to die… that you had to write a goodbye to me. They nearly killed you and I couldn't do anything about it, Kate. I failed you…" His voice cracked at the end and he had to take a few deep breaths to keep the panic from rushing back in.

She reached out and gripped his hand. A tight hold to try and give him back some of the strength he had given her today, a strength he seemed to desperately need now. "Rick, look at me." He kept his eyes locked on their hands, refusing to look at her. She sighed and began to swipe circles over the back of his palm with her thumb. "Rick, nobody knew what I was going to walk into today. And I know you did everything in your power to find me, that you never gave up and I love you so so much for that, Rick, and for that reason you could never fail me." She leaned in and lightly pressed her lips to his in a gesture the hoped could convey all she could not put into words. "I meant what I said, you are an amazing man and I love you so much for what you did for me that day, what you do for me every day. Please, please believe that."

She could start to feel the sting of her own tears behind her eyes. She needed him to understand what he means to her and she wonders if this self-doubt is about more than just today. But that is something for another time. Right now she needs to comfort her fiancé. She squeezes his hand again and waits until he meets her eyes. His beautiful, deep blue eyes shining in the sharp contrast of the red-rims that surround them. It's sad, she thinks, how beautifully blue something can be and yet radiate so much pain. Right now she just wants the pain to go away. For the both of them. "You save me everyday just by being here, by not letting me fall. And I'm not gonna let you fall either, Castle, okay?" His lips turn up slightly to give her some attempt of a smile, and she takes it. She knows he's going to be okay.

"Lets go to bed Castle," she whispers, leaning in to kiss his lips before standing and tugging on his hands to pull him up. As soon as he is standing he hauls her into his chest, wrapping his arms tightly around her. "Thank you," he whispers into her ear and she can hear so much in those two words, the words he's not saying.

"Always."

Thanks for reading! Please read and review!

Also please check out the fanfiction I am collaborating on with the lovely Tabatha called A Life Worth Living by CaskettBuddies:)

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