A/N- I've been sucked into the heaven that is Caskett shipperville and feel the overwhelming urge to write. I'm actually waiting on another piece to find a beta reader and so tapped this out to keep the mojo flowing. I might expand on it once I get my other completed story up here. I really do feel the need to write a case-fic.

I've not posted in this community before (or posted at all for years) so feedback, constructive advice and comments are always appreciated. Any spelling mistakes you might pick up too! This has not been beta'ed in any form, so apologies for anything hinky.

Purpose

The usual bustle and energy of the twelfth precinct was muted as Castle stepped off the elevator and made his way along the corridor. The late hour meant the majority of its customary workforce was home. In bed. Asleep. Castle stifled a yawn and reminded himself that at least he chose to be here at this godforsaken hour. Detectives Beckett, Ryan, and Esposito were not so lucky with their flexible choice of office hours.

A body drop at 10pm the previous night had meant that no one had gotten any sleep from the day before and now, coming up on six hours later, it was looking unlikely that they'd be getting any today either.

A lawyer from the justice department had been found murdered, her throat slit, office ransacked. She had specialised in juvenile cases- family law- she had made it her life's calling to speak for those that otherwise would not have had a voice loud enough to be heard.

Kate was taking the case hard.

Castle rounded the glass partition and stepped into the bullpen. Ryan and Esposito both looked up at his approach. Both stared at him in earnest; their foreheads furrowed. With a slight tilt of his head Ryan indicated towards Beckett, who sat perched on the back of her desk staring at the murder board. Esposito was less subtle, he pointed fiercely, and mouthed, "Go!" his head nodding in his boss's direction.

Castle looked again at the tough-as-nails Detective as she sat, slumped, on her desk. The soft curls that, earlier, had framed her face were now twisted and tied in a hasty ponytail. Her skin was paler than usual and Castle wondered if she'd had a chance to eat dinner before the call had come in last night. He looked down at the coffee he'd bought and wished he'd thought of dinner, or breakfast, instead. Closing the distance between them he waited until she turned to look at him.

"Hey" he said quietly, gently touching his fingertips to her knee in comfort. His hip pressed tight against her side as he shuffled onto the desk beside her. He winced as he heard a pen caddy fall over spilling pens and markers, and a paper cup (almost empty, thank god) hit the floor as his bum dislodged paperwork and files from their previous piles.

A muffled snort broke free from Beckett's mouth and she hastily turned away to cover her smile. "Is that you trying to be quietly reassuring, Castle?"

"Perhaps that was me trying to make you smile. And, if evidence serves me, I can see that it worked." He countered.

"You're pathetic." The hint of a smile took the sting from her words.

"You wound me, Detective." He bantered back, prolonging the diversion from death as much as possible.

"Adorable. But pathetic nonetheless." She muttered under her breath just loud enough for him, and him alone, to hear.

"I bought you coffee. But I can see now I should have bought you food."

"Why's that?"

"You're sounding a little punchy. And you're skin is far from its usual radiant glow. I'm thinking you're already running a little high on caffeine and a little low on carbs."

"Shut up and pass me the coffee, Castle."

"Your wish..." he said, handing over the latte. "But I'm going to order something to eat. Unless," he trailed off, searching her face for clues as to how the case was going, "unless you intend to head home for a bit, catch some sleep?"

"Not yet, the boys are running down a couple of solid leads and I want to be ready to question the aides at her office when they start at seven."

"Okay, I'll run out and get burgers and milkshakes."

"Get them delivered." She countered.

"Okay." He replied, agreeing with her demand, but his eyes sought hers; questioning.

"I could use you on this. Your opinion," Beckett sighed and turned back to the board. She was quiet for a moment and Castle waited her out. "I'd like you with me for this one, Castle," she whispered.

"Then I'll stay. You know that, Kate." His promise of 'always' echoed in his head.

"Yeah, I do." She found his fingers where they rested beside her knee and squeezed his hand briefly before standing up. "I'm going to go splash some water on my face. Tell me what you see when I get back?" she asked, and her eyes flicked briefly to indicate the timeline laid out across the murder board.

"Okay." His voice was rough, pitched lower than usual. Kate took a moment to truly look at the man in front of her, and she smiled, her thanks communicated without the need for words.

Castle waited until the sound of her footsteps was muffled by the turn in the corridor before standing up and reaching for the phone. He glanced briefly to his partner's teammates and the twin nods they gave him swelled his already too-full heart to overflowing.

Acceptance. Gratitude. Purpose. It really didn't get much better than this.