So, this is something a little different to my usual field, but I'm hoping you guys will enjoy it all the same.

Disclaimer: I don't own Castle, but that doesn't mean Castle doesn't own me.

Put a bullet through his heart.

Put a bullet through his heart, or he'll put another one through Kate's.

The words were almost a prayer, a mantra repeating over and over in his head. Castle kept his eyeline aligned perfectly along the length of the barrel, his gaze fixed unwaveringly upon his foe. His mind was clear, his hands steady. He knew his choice.

His grip tightened, his finger curling closer around the trigger like a lover's embrace. Silent moments passed as he hovered on the precipice, waiting to tip over the edge; the tiniest squeeze would be enough, and it would be done.

His heart, or Kate's.

Time to choose.

Don't think. Just breathe.

Castle took a deep breath, and squeezed.

The shot sounded muffled to his ears, though he saw it reach its target clearly enough. Without pause, without thought, he squeezed the trigger again and again; the first shot had opened the floodgates, the water rushing through, and there was no stopping it now. Focused, unflinching, he unloaded round after round, firing until his magazine was as empty as he himself felt.

Lowering the gun slowly, Castle surveyed his enemy.

Dust and confetti-like black scraps drifted around his victim, slowly settling to the floor beneath his man-shaped silhouette. Instead of several, the target bore only one puncture mark; a little bigger than a large coin, the ragged hole pierced directly through the silhouette's dark heart.

There was no triumph in this achievement, however; no pride in his prowess. Castle's expression remained hard, unchanged, his only response being the small, automatic movement of his hand as he resolutely pressed the retract button. With a practiced fluidity, the old target was discarded– joining an ever-growing pile of identical victims– and a new one placed in its stead, an unmarred twin to replace its fallen brother.

As the newest sacrifice reeled back along the line, fluttering and flapping with the momentum, Castle expertly reloaded the gun, took aim, and emptied yet another clip, all before the target had come to a halt; yet when it stilled, it too bore the wounds of the one before, the neat cluster of shots grouped closely in its center. Slapping the retract button, Castle mechanically repeated the process, emptying round after round, clip after clip, until the pile of black ghosts beside him had doubled, then tripled, each one bearing a near-identical wound.

His heart, or hers.

It had been Ryan and Esposito who had brought him down here, just days after Kate's shooting. Straight-backed and solemn-faced, the three of them had lined up side by side, barely exchanging a word as the black targets were discarded, one by one. Beckett had survived the bullet that had been sent for her; it was an unspoken pact between them that the man responsible for it would not receive the same fortune.

Back then, Castle could not have hoped to match the skill of his two brothers; despite past training and experience, the events of the funeral had left him sweaty-palmed and trembling when a gun was placed in his hands, leaving him barely able to breathe, let alone aim. But together, the three of them had gotten him through it, returning again and again– until eventually, their weekly sessions had become less and less regular, dwindling until it was Castle alone who returned week after week, sometimes more, losing himself in the endless pattern of fire and reload.

It was there that she found him; sitting on the floor of the firing range, surrounded by small islands of piled silhouettes as he stared unseeingly at the gun clasped in his large hands. The soft sound of her clearing her throat caught him, breaking into his trance and pulling him back to the present, back from the place where he'd been, one far away and full of screams and tears and blood.

Looking up, he blinked, then blinked again, his gaze sharpening as he registered the figure before him.

"Captain."

It wasn't a statement, not quite a question, but somewhere between. Dimly he realized he should stand, eject the clip, and attempt at an explanation, but his brain refused to comply. Instead, he simply looked back down at the gun resting in his large palms, breathed deep, and spoke the words that had occupied his mind ever since the moment he had known Kate would survive.

"I can't let him get another shot at her."

As soon as the words had left his mouth, he felt his knotted muscles loosen slightly, his breath releasing in a slow, steady exhale. It was a relief, somehow, to admit it aloud, to confess the secret that he'd so carefully kept hidden from all but his two brothers. Like a never-ending nightmare, it was a truth that had come to shadow his every moment, a darkness that had spread to fill his mind and body like a slow-moving poison, steadily consuming him from within. Whatever it may cost him now, whatever consequences would follow, he could not regret his admission; already he felt the burden lightening, the oppressive darkness lifting just slightly, leaching out of him to sink into the walls and floor, drawn away like spilled ink into a blank page.

Keeping his eyes down, he breathed slowly and steadily as he ran his thumbs back and forth over the cool metal barrel, waiting calmly for the rebuke, the shouting, the furious orders to get out and not come back.

But none came.

After a few more moments of silence, he slowly lifted his head, looking up to see her regarding him thoughtfully, her eyes indecipherable. Then, without a word, she stepped closer, silently reaching out her hand.

Holding back a sigh– this was it, he was done, she would surely find a way around the mayor's orders somehow– he slowly lifted his hand to place the gun in her waiting palm, feeling as though he was giving away his life with it.

Something like amusement flashed in her dark eyes, a soft huff escaping her lips. Accepting the gun from him, she placed it aside on the small counter, then reached down once more, offering her hand to him.

Staring at the proffered hand in open surprise, Castle hesitated, then wrapped his hand around hers, letting the petite, firm-gripped woman help him to his feet.

Once he was standing, she dropped her eyes from his and looked back down at the gun, before calmly picking it up and expertly checking it over.

Her eyes still inspecting the service piece, she spoke quietly, her words seeing to come from a distant place deep within herself, one buried far deeper than she would normally ever let anyone see.

"We're not so different, you know, Castle," she murmured quietly, lifting the gun briefly to check its aim. Watching her, he saw the tension in her muscles, the almost imperceptible twitch of her finger against the trigger before her grip loosened, the gun lowering.

He was still staring at her trigger finger– wondering what personal ghost she had just mentally slain, and whether they had ever received justice for whatever crime they had committed– when she spoke again, her voice soft, serious, and laced with a darkness of her own.

"We do what we have to do to protect the ones we love."

After another long, contemplative moment, she sighed, then turned to him, placing the gun back in his hands and curling his fingers around it, her small hands surprisingly gentle.

Her eyes lifted, fixing firmly onto his, and when she spoke again, she sounded almost like her usual commanding self.

"Just don't ever put me in the position of having to send my detectives after you, Castle," she ordered dryly, ignoring his silent, thoughtful stare as she continued, "Because I don't think I ever want to know where their loyalties would lie."

Then, without another word, she simply turned and walked away, leaving him staring wordlessly after her, his thoughts still far behind.

By the time he remembered how to speak, she was already at the door, one hand curling around the smooth handle.

"Captain?" he called, his voice slightly hoarse. When she paused, turning back to look at him with eyebrows raised, he continued uncertainly, "You won't– you won't tell Beckett about this, will you?"

Gates arched a brow. "Tell her what, Castle? As far as I'm concerned, this conversation never happened, and neither of us were ever here."

Turning again towards the exit, she pulled the door open, then paused once more, speaking over her shoulder.

"However, perhaps there are a few things that you should tell her."

Castle blinked. "Sir?"

For a long moment there was silence, but when she answered, her voice was strangely wistful.

"Even the strongest woman fears to risk her heart, Castle. Just don't let her hold herself back too long."

And with that, she stepped over the threshold, and was gone.

For a moment his eyes lingered at the door, staring after her, before he looked down at the gun in his hands, silently contemplating her words. Then, he put the gun down, and turned for the door.

He needed to find Beckett, to finally tell her the truths that he'd kept from her for so long.

Because, after all, Gates was right.

They'd protected their hearts for long enough.

So... I have to admit, that did not exactly go as planned. I'm a little unsure as to how it turned out, actually, so if you have any suggestions for potential alterations, please let me know.

On a fairly related note, I really don't think enough people give Gates the credit she deserves. She has been steadily warming up to Castle, even making an effort to see where he truly fit into the team and whether his insight proves to be valuable or not, and yet everyone assumes that she's just going to get rid of him the first chance she gets. Personally, I think she's more perceptive than that; I think she realised quite a while ago how central he was to the team, but she's just not the type to broadcast her thoughts out to the public.

(In fact, see the 'Other ficlets' link on my Tumblr page [google "idealisticrealism"] for a 700 word OS on Gates' backstory and general view on Caskett)

So yeah anyway, felt it was time for a bit of Gates appreciation. I hope I wrote her okay, and if not, please let me know, because I really want to do her justice.

As always, thanks for reading!