Disclaimer: I don't own Castle, which is good, because I don't think this plot line would play out too believably on TV.

Your Last Day

Prologue

Kate rolled out of bed with a slight groan as her sore feet hit the ground. She'd spent the previous day fruitlessly running down suspects and canvasing for witnesses with Castle and it had left her feet sore and her mind set on wearing more sensible shoes to work.

That resulted in a crack from Castle, because, of course, he noticed that she was wearing tennis shoes over her normal footwear. "Going for a run?" he'd asked casually as he set her coffee on the desk.

She ignored the comment and continued to review the murder board, hoping for inspiration, however, he seemed unable to contain himself, "Where do crazy runners get their exercise?" she simply raised an eyebrow as she seriously contemplated his own level of sanity, but he seemed to take that as her asking him for the punch line. "On the psycho path." he'd responded, grinning like one himself, but disappointed when it didn't even get a tease out of her about his lack of comedic talent.

The day flew by like any other and clues fell into place. A suspect emerged and they headed out to his place, though all indications seemed to be that he had likely skipped town by then.

With no answer to their knock, Esposito kicked the door in and they split off. Castle stuck with her as Ryan and Esposito moved off to the left side of the apartment. She hadn't thought much of it, unassuming really, the musty closed in feel of the air seemed to indicate no one had been there in a long time. She soon realized that it just meant the resident didn't care to open the windows.

Rounding the corner to the bedroom, Castle had started to say something as her gun swept casually to one side and her eyes tried to take in everything at once. It was the barest of seconds before she heard the scream from beside her, "Kate!"

It came at the same moment as gun fire and she was tackled to the ground.

Glass breaking signaled the shooter's attempt to escape and pounding feet informed her that Ryan and Esposito were racing into the room, but she couldn't get up and pursue the man with Castle still lying across her. He felt heavy against her chest that ached slightly from the impact of his body throwing her to the floor.

"Castle, I'm sure this is a dream come true and all, but he's getting away!" she informed him with exasperation, but was surprised when he didn't move or even acknowledge her.

Sudden panic flooded her as she frantically began to push at his chest. Sliding him off of her and scrambling to her knees beside him as her fellow detectives burst through the door. Thoughts of pursuing the suspect fled instantly as she finally registering the gurgling sound that interrupted the steady ringing in her ears and the sound of blood pulsing through them.

Terror coursed through her as her gaze fell on the exit wound low on his throat. He'd taken the bullet from behind and it had torn through the soft flesh of his neck, easily coming out the other side. She watched frozen in place as his frightened eyes searched for hers, his breathing raged and forced as blood pooled in his airway.

Time seemed to stop in that instant as he gazed up at her as if pleading for it not to end this way, but also with a purpose as if there was something he needed to say before he ran out of time.

She knew she couldn't fight the hands of the clock as one garbled wet breath later everything stopped. His brow was no longer furrowed in pain and confusion. His eyes no longer begged her for anything or tried to convey that which his shatter voice box could not pull through his blood soaked lips. His hand, that she hadn't even noticed, let go the tight hold it had taken of her shirt and fell to the ground.

Life blurred from there as she knelt in the spot, unwilling to leave his side until she was dragged away by Ryan and Esposito so the coroner could do his job. She didn't know how long she fought them to go back to his side, but it was a battle that she finally lost the will to fight.

She couldn't call his family, couldn't face them, not when she had failed so miserably to keep him safe. Instead, she took the coward's way out when Ryan's voice quivered as he asked if she wanted him to call them for her.

With tears pouring down her face she finally wrenched herself away from the two detectives, briefly registering their own grief shining in their eyes, but unable to do anything about it.

Her heart ached and she wanted nothing more than to get away from this apartment, go where she didn't have to think about what this all meant. How the end of one man could feel like the end of so much more.

She didn't see the streets as she moved swiftly, glad for her choice of more sensible shoes, but forced back to thoughts of Castle's joke just that morning.

She didn't know how long she ran, but eventually she had started to walk and after a long time she sank onto a set of stone stairs in front of a random apartment complex and buried her face in her hands. Tears moistened the dried blood on her hands and she suddenly wanted it off of her.

Knowing she'd never catch a cab in her condition, she took a minute to gauge her location and with a new purpose and a second wind, she began to run again. Feet slamming the pavement as they carried her forward. The sun setting behind her as she finally arrived at the precinct seemed to taunt her with yet another end on this day that was far too full of them already.

At least, that would mark the end of this day that never should have been.

She turned over her clothes as evidence, gave her statement like a zombie, and accepted the offer of a ride home from Karpowski. She wasn't in the mood for conversation and was grateful that the other detective seemed to realize that.

Slipping into her apartment, she instantly shed the track pants and t-shirt she'd dawned at the precinct and took in her condition in the unforgiving light above her bathroom mirror. She was virtually unscathed, a small bruise along her shoulder, the blood she hadn't been able to scrub from her hands, what had soaked through her clothes, the smears she hadn't even noticed on her face. But her eyes startled her. She knew they'd be red rimmed and swollen, but she hadn't expected to look up and find them so hallow and empty.

The water was too hot, but she didn't care as she scrubbed at the blood on her hands, face and where it had seeped through her shirt and the knees of her pants. She scrubbed until the water ran cold, scrubbed until her skin burned a bright red that had nothing to do with his blood. The pain brought her back to her senses as cold water sprayed from her showerhead.

She didn't bother with more than throwing on her robe as she climbed into bed, clutching her pillow and willing the day away, not looking forward to the conversations she would inevitably face when the sun rose again.

She cried for his family, his daughter and mom. She cried for his friends and her partners. She wished she could take the pain from them, lift the scar this would leave in their lives. She hated that at some point the tears started to fall for her.

She had no right to feel this way when it had been her fault. She had no right to mourn the loss of his smile or the way his left eye blinked just slightly faster than the right when he had been staring at something too long in heavy concentration. She had no right to mourn the teasing glint in his eyes or that smile she always faked a lack of reaction to. The one that sent a bolt of heat straight through her a moment before he said something completely inappropriate. She had no right to mourn the fact that she had never taken him up on a single one of those offers.

Whether she had a right to or not, the thoughts came unbidden with the knowledge of her mentors words ringing in her head as if a vicious taunt from the universe. "If only."

'If only' would be her life now. The whys would consume her. She could already feel it eating at her from the inside out. She was actually grateful when the headache came, the knowledge that her tears had brought on pain that was rightfully hers to carry. She felt shame, piled on regrets, wrapped in guilt and she knew that there was nothing she could do about any of them anymore.

She hadn't even been there when it mattered most. Instead, she stared at him in shock as the lights went out without even opening her mouth. She could have at least let him go out with some kind of kind words or reassurance, but even in his last moments she had failed him.

That night, Kate Beckett cried herself to sleep for the first time in nearly a decade

x.x.x

Chapter One

Tuesday

5:45am

Kate woke to the sound of her alarm clock. Without thinking, she slammed the snooze button and fell back on the bed her throat suddenly tight and tears in her eyes as her the night before came back in intense, violent detail. Looking down at herself, she was surprised to see she was dressed in her pajamas and she let her gaze slip to where she knew she'd spot the pile of gym clothes on her floor.

Instead, her eyes fell on the shirt she had laid out the night before and sudden visions of it covered in blood assaulted her as she realized two things. The first was the relief that it had all been a dream, the second was the knowledge that there was no way in hell she was wearing that shirt today, possibly ever again.

The dream had felt so real and played out until she dreamed herself falling asleep at night as opposed to thrashing awake during the height of emotion. The end of her dream bleeding into her awakening in the morning left her disoriented. For longer than she cared to think about, she lay in bed fighting back the tears as she willed herself to believe it really was all just a terrible nightmare.

It felt like a familiar one, something she had been through before, but she couldn't remember ever having had the pleasure of that particularly vivid dream. Of course, there had been plenty of others, but never that exact set of circumstances. Never that outcome and she had never been forced to see herself through the aftermath.

She'd had dreams where she failed to protect someone before, but she always woke up searching for the blood on her hands from trying to hold them together after the fact, not confused as to whether she had actually dreamed it or if it had been real. This one hit too close for comfort.

Feeling more than a little foolish, she pulled her cell phone to her, absently noticing that it was Tuesday. Something registered that it had been Tuesday in her dream as well, but she shrugged the finer workings of her subconscious off. She didn't even have to scroll through her message log to see that the last one she had received was from Castle at nearly midnight the night before.

She felt herself breathe a little easier as that confirmation of reality sank in. She allowed herself to lie back in bed and really think about what she had been subjected to over the course of her night's sleep.

She was stunned by the realistic nature of the nightmare that had tormented her sleep the night before. It started with her waking up and ended with her going to sleep that night, but there was so much detail in between that usually didn't accompany her dreams.

Normally, she could find herself mysteriously in a dark warehouse, crates and boxes stacked high and impeding her view as she tried to pursue a suspect, or running down a dark alley that never seemed to end. This time, she hadn't been suddenly dropped into the action and she wondered, with a chuckle, if she could blame Castle's influence for that. Perhaps all the talk he had spouted over the years about having the whole picture had forced her mind into some new and frightening world of dreaming where she woke with a feeling that it was real. If that was the case, he'd have hell to pay for it because this type of dreaming she could definitely do without.

She had enough to worry about without waking in a blind panic to the thought that had raced through her mind first thing this morning.

Even now, thinking back on the dream, it felt real, like it was an actual memory in her brain and she wondered how long it would take to work over those thoughts and for the images to fade.

With a laugh at how weird brains could be, that she pretended there was actually a hint of humor in, she slipped out of bed and groaned as her feet hit the ground. They really were sore from all the walking she had done the day before.

With a shrug, she headed for her living room for a little exercise to burn off the lingering adrenaline from her dream.

8:04am

She spotted Castle as soon as he entered the bullpen, immediately shaking off recognizing his blue button up shirt from the night before. It did appear to be one of his favorites, which was the logical explanation for its appearance in her dream the night before. Despite the knowledge that her dream had been just that, a figment of her imagination, she still felt her heart rate increase on sight of him and a warm feeling of relief settled over her as he cast her a cheesy grin and slid the coffee onto her desk beside her.

She finally tore her eyes away, knowing it wouldn't do well for her to be staring at him all day. His voice cut into her thought with a casual question that set her blood to ice, "Going for a run?"

She ignored the comment and continued to stare blankly at the murder board, hoping that the next words out of his mouth would be something Alexis did the night before or some kind of insight on the case. Instead, he sent her head spinning as he asked, "Where do crazy runners get their exercise?"

She turned her eyes, to bore into his own, wondering how he could know the details of a dream she'd shared with no one. The lump in her throat from this morning returned as he shrugged at her lack of response and finished, "On the psycho path."

Without warning, tears from the night before flooded back into her eyes and his gaze suddenly became serious and concerned. Despite his eyes, his tone remained light as if he were trying to keep attention diverted from them by acting natural, "Come on, it wasn't that bad of a joke."

But his eyes betrayed the real question and she knew she couldn't answer it. Instead, she shook her head and blinked the moisture away, grabbing her coffee cup and taking a few deep breaths under the guise of casually sipping the hot beverage. Her mind was racing with the improbabilities of this day unfolding as it appeared that it might.

Whatever the reason she had been given the glimpse she had apparently been blessed with, no matter the insanity she felt seeping into her bones, she also felt relief. She was suddenly, and irrationally, determined that if this day played out as the one before had, she would be ready for it this time.

She would do what she should have done before and keep him out of harm's way.

x.x.x

A/N: This popped into my head while listening to the radio and I had to jot it down. It was loosely inspired by the song If Today Was Your Last Day by Nickelback. I don't know how this came from that, but as it did I paid homage to the song with the title.

Obviously, from where we've been so far, this will require you to have a very open mind. Just remember, we're all here to have a good time, so come play with me as we delve into yet another world I've never written for.

Don't be scared as you read, despite what you may be thinking, this is not a death fic. If you know my work you know to brace for a bumpy ride, but that everything turns out (relatively) ok in the end.

Preview that made my day: Beetlebug, for encouraging me to stretch my wings wherever the inspiration takes me, without whom I'd still be thinking about this story incessantly, but have none of it actually written.

Thanks for reading.