A few disclaimers:

I'm new to Castle this season, and I don't know that I have the characters (their motivations, their personalities) completely figured out, yet, so please forgive any inauthentic representations. I'm also new to fanfic writing, so we'll see how this goes.

A note on this fic: it's perhaps a bit darker in tone than the show itself, but I felt compelled to write it after seeing the inner turmoil Beckett confronted in "Kill Shot." This isn't exactly on point with her transformation in that episode, but it draws on a similar emotional rawness. It is not set after a particular event from the show, but instead follows a life-and-death-style event that Castle and Beckett encounter during an investigation. It jumps between POVs a bit, as well as between closely related time periods (present to recent past to present), but I hope it isn't too convoluted.

Oh - and, of course, I don't own the show or its characters.

After all of the chaos and the expectation of their impending demise, the most jarring thing in the aftermath was the stillness. The dim features of the still-standing factory walls became clearer as the smoke settled, and as Kate Beckett's eyes and ears adjusted to the darkness and the quiet, she found Castle - swathed in dust and shadows, but seemingly unscathed – standing several yards in front of her.

...

Moments ago, they'd both been racing through the maze of metal and machinery, bullets ricocheting off the surfaces to their left and right as they fled an armed suspect who'd set up shop in the abandoned factory. Castle had warned Kate, as they'd approached the place, that it would be a bad place for a confrontation. Inside the decaying refinery were a network of multi-tiered catwalks and passages that would be all the more difficult to navigate in the dark. And then there were the tanks of combustible solvents still lingering in the building, which would make for a veritable explosive nightmare, in the right (or wrong) conditions.

They'd expected to catch the suspect unaware and close in on him before he could run or pull a weapon, but he'd spotted them first, and he'd had them on their heels in seconds. Kate had shoved Castle to the right as they'd approached a fork in the grated catwalk, and she'd leapt left in order to split them up and make them more difficult to track. They'd both continued running along the lofted pathways, scrambling down twisting staircases and frantically searching for the ground floor that was their only chance of escape. They'd known the odds of getting out unscathed in this kind of situation, and the bullets pinging off of the metal tanks over their heads convinced Kate it was only a matter of time before one exploded and took the factory down with it. Her mind had flicked back and forth between her own safety and Castle's. Their luck was about to run out; she'd felt it.

At last, her feet had hit solid cement, and she'd spotted movement to her right. Before she'd been able to grab for her gun, she'd heard Castle's voice – winded and worried – shouting her name. She'd reached out as he'd thrown his hand in her direction, and both of them had continued sprinting toward a faint light at the far end of the building.

And that's when the room had exploded.

With a deafening roar, flames had torn over their heads and sent them both reeling. Fiery shards of metal had crashed around them, illuminating the scene. The part of the building from which they'd just escaped had come crumbling in on itself, detonating and demolishing everything around them. Kate had braced herself, tucked herself under a web of piping, straining to see through the smoke as the barrage of heat and noise shook the world around her. The image of Castle lying helpless and injured somewhere out of reach had struck in her more terror than the prospect of her own safety. And in that moment, something inside her had shifted.

...

It might have been a minute later – or five, or ten – but eventually, the noise and the chaos faded. The remnants of the factory's ground level came into focus, leaning at odd angles and still smoldering in places. She extricated herself from the twisted pipes and scrambled to her feet to find Castle, silhouetted against the smoke about ten feet away.

And now here they were, standing in the darkness, staring blankly at one another, nearly immobilized by shock, but flooded with relief. Castle's features were too obscured by shadow to interpret, but Kate could tell by his posture that he was unharmed – his shoulders were square and strong and his arms moved almost phantom-like as he swiped the dust from his jacket sleeves. Kate's heart was pounding; her ears were throbbing. She'd gotten them into this, and she'd nearly killed them both. Anger and frustration flared deep inside her, as she contemplated the devastating loss that might have befallen either one of them, if only one had escaped. She couldn't tell if the heat in her face was her own rage or a lingering affect of the explosion, but standing there, unmoving, it threatened to consume her. What if she'd lost him? It would have been her own goddamned fault. Her own selfish pursuit of another criminal would have destroyed the most sustaining, meaningful thing in her life.

But, she reminded herself, Castle is okay.

And she was okay.

Suddenly, the distance between them was more overwhelming to her than the whole of what they'd just experienced. Her nerves were so sharp, she felt poised to burst – if only to rectify the frustrating incongruity between the vibrant pounding in her veins and the vacuous stillness around her. With her breath coming ragged and uneven, she felt the foggy shock of the event dissipate. In it's absence, she became acutely aware of her own vulnerability, and to match it, a wildly bold resolve. She had the irrepressible compulsion to connect to him, and their distance was at once physically painful.

So in an instant – a moment not entirely devoid of grace, but driven by a rawness that revealed the desperation behind it – she closed the distance between them. Her whole body came crashing into his, her hands and forearms connecting first with his chest and then grasping at the fabric of his shirt, his face, the back of his neck. Her mouth crashed into his with such force that he swayed backward, taking a step back against the dusty wall and sending the debris at their feet swirling. His eyes had snapped shut the instant his mind had connected her actions with her intent, and his arms flew up to catch her and envelope her as they collided. Kate drew back with a sharp intake of breath, but upon finding no resistance in his eyes, she brought her lips back to his with greater urgency.

...

Castle was still thrown. He felt his mind lagging several seconds behind his body, even as he melted into the moment. He reciprocated her fraught kisses while trying to make sense of her frenzied movement. His own nerves were frayed by the near-death event, but he couldn't reconcile the way he felt with the way Kate was reacting. He knew she must be grappling with something deeper than the shock, and he was here for her. But he didn't want her like this – all reaction and regret and adrenaline. He wanted to soothe her, to find the truth behind the misdirected aggression. There would be time for fervor later, but now she needed to process, to reflect, and to recognize the support that Castle was always there to provide. Always.

Kate's kisses were forceful, but he met each one with soft lips, taking her in, drawing out the motion until she could feel his sincerity. His arms wrapped gently around her body – still a live-wire – and his hands pressed firmly against her back, holding her squarely in the embrace and stilling her anxious movement. He sucked at her bottom lip, forcing the rhythm to slow, and he finally felt her body begin to relax. Her grasp on his shirt loosened, and her hands relinquished the crumpled fabric; her palms came to rest open on his chest. His kisses were laced with something strong and protective, eliciting from her a soft, guttural whimper that betrayed the tears beginning to burn behind her eyes.

...

She was coming undone, and this is how he was going to see it – she had flung herself on him as though the shock of the event had elucidated their every emotion and intention. As though a physical connection in that moment could have rectified not only the distress and shock of the event, but also their years of missed opportunities. It wasn't fair to have committed this act so disingenuously. She owed him so much more. Their moment should have been purposeful, personal, and untainted by the emotionally overwrought events of a case. It should have been something uniquely theirs.

Instead she'd let this event and her own internal conflict push her over that threshold she'd thus far been so careful not to breach. Before, she had been wise to keep separate the personal and the professional. After all, she could afford to be neither reactionary nor dependent in this line of work. But now she'd gone and muddled the whole thing in a way that could not be salvaged by a few cups of coffee or a playful retort at work. How could she repair this? How could she show him that he meant so much more to her than she'd been willing to let herself recognize? How could she apologize for throwing herself at him in anger, instead of love?