A/N: This has been my first fic in a year, and my first multichapter in this fandom. Thank you to wonderful ellie (closingdoors/instanakaticshair) for the beta.

Summary: This can't be happening. It just can't, because she's survived bombs and bullets and gunfights. Beckett is a fighter, but there's not much fighting she can do against her own body, the disease that could kill her from the inside out.

a sickness in my bones

chapter one – fifty percent

Kate gets more shit than she deserves, and he's known that since he heard her speech falter as she told him about her mother's murder. His belief is only affirmed when he realizes just how much of a parent she was forced to be to her own father during his alcoholism, and again when she falls from the podium with a bullet in her chest.

And then she shows up on his doorstep soaked to the bone, and they begin their own little piece of happiness; and it might be naïve, but he really believes that things might be better this time. They have a few months of being blissfully happy and everything is perfect and they fall to bed together and wake up next to each other and he pinches himself because it's finally happening - not just for them, but for her, and for once her life isn't under threat and no one she loves has been killed and she might just be happy for the rest of her life.

Then she gets taken down on the job. She gets straight back up and slaps cuffs on the guy, but she hit her head on the sidewalk. Of course she doesn't want to go to hospital, but he makes her, because she has a concussion and he can excuse being overbearing because he has a right to as her boyfriend. It's a run of the mill head scan, just to see if there's any damage. Even Castle doesn't expect anything, he's just being cautious. They wait for a while to be seen - it seems like they came in during a rush hour of patients or something, because everybody looks swamped. When her name finally gets called and they are lead to an examination room, Castle does the talking, always the smooth and charming gentleman. He explains what happened, that they'd just like to get her checked up to be safe. The doctor sends her through for an MRI and some other scans he can't remember the name of, procedure for a head injury they tell him. When she's finished with, the doctor says they may as well wait for the results because he's put a rush on it (something about doing what he can for New York's finest). They only wait for an hour before they get called through.

It only gets worse from there.

He knows something's wrong when the nurse comes through the swinging doors and asks her to come and see the doctor. The look on her face doesn't say "We're good to let you go home". So he gets a nervous feeling in his knees; like he did just before he caught the glint of the sniper's scope in the cemetery. The nurse leads them through at least five sets of double doors into what looks like some kind of lounge area. Bad news. This is the bad news room. Castle can't stop thinking about it, brain going at a mile a minute. They sit down at a table with the guy that took her head CTs.

"Ms Beckett…" He starts. He looks like she does whenever she has to tell someone that their child or partner or sibling is dead.

"Please, Kate." If he's going to tell her there's something wrong with her (and that must be what he's doing, she knows that look, she's worn that look) then she wants them to be on a first-name basis.

"Kate… The results of your CT and MRI scans came back. I'm sorry, but we've observed a tumour on your brain. This could be a result of your accident, but it is possible that it's been there for longer. Judging by the size, it's fairly recent, so it's good that you came to see us. The earlier we catch these things, the better chance we've got of you getting better."

"And what is the chance of me getting better?" She hasn't quite processed it yet, but the procedural part of her brain is already asking the right questions.

"It's hard to say exactly, Kate, but right now we think we're looking at a 50% chance of recovery."

"50/50?" Castle breathes. It's the first time he's spoken.

"That's what it looks like." Kate doesn't flinch. Always the fighter.

"So what comes next?"

"For tonight I suggest you get home and get some rest. Nurse Robbins will give you an information pack to have a look at, and we'll call you to arrange an appointment over the next week to discuss treatment options."

"Ok." Kate smiles warmly at the guy. Why is she smiling? "I guess I'll see you soon."

She gets up and heads out the door, Castle doggedly following her. She doesn't break her stride as they weave through the corridors back to the waiting room, not when they pass the front desk to get handed that information pack, and not even when they walk out the hospital doors. He keeps waiting for her to break down, to cry, it's what he would do - but her eyes aren't even moist.

They drive home in silence, not saying a word to each other. The doorman nods to them, can read the expression on Castle's face that says don't smile at me tonight and just lets them straight through. They don't speak in the hall. They don't speak in the elevator. They don't speak in the corridor. It's only when he opens the door to his apartment and turns to close it behind her that she falls apart. He turns around and she's in pieces, arms curled around herself as if it's the only thing that can hold her together. Tears spring to her eyes and her lip trembles in a way that is utterly heartbreaking to watch.

"Castle…" Her voice is bare and broken. "Fifty percent."