A/N: Set during 1x05 (A Chill Goes Through Her Veins).

This turned out a lot differently than the original idea in my head. Not sure if that's a good thing or not.

She had spent her entire evening at the precinct, stalking back and forth in front of the murder board, scrutinizing the daunting pictures and her own neat, handwritten notes beside them, willing the answer to come, for Sam to tell her how he had killed his wife. But the truth only continued to elude her and further her frustration.

Something wasn't right in the Cavanaugh case and it was gnawing at her like an itch she was unable to scratch. The people involved - the victim's family - deserved to know the whole story. Not a theory they thought to be true. It wasn't enough for them, and it wasn't enough for her.

And that was why Detective Beckett had ended up at his building, greeting his doorman with a forced smile and quietly cursing to herself during the smooth ride up the classy elevator to his floor. He was simply a last resort, someone to brainstorm with. That was all.

After being let in to what seemed like a madhouse – a gorgeous madhouse that had her eyes widening as they scanned the spacious vicinity of his loft when his back was turned – by Castle and his daughter, both glowing blue and green in what looked to be some kind of laser tag gear, and his effervescent mother with her welcoming, white smile standing out against the mint green of her facial mask, Castle led her into his office.

She made a comment, comparing the room to the Batcave, and he'd equated her to the famous comic book character, pointing out the similarities.

Loss of a loved one leads to a life of fighting crime.

She had taken a moment to examine the Nikki Heat murder board he had created, noting the similarities to the one she used at the precinct, and then he'd asked her what was wrong, his voice heavy with curiosity. She didn't fault him for that; she had been the one to show up uninvited at his home without stating her reason for being there.

"I can't find it." she said, gritting her teeth and keeping her back to him, feeling the thick tendrils of failure twisting around her insides like barbed wire.

"Find what?"

"The answer." she replied, turning back around and letting her hands drop tiredly to hang at her sides.

The curiously puzzled expression blossomed over his features as he studied her for a moment and she found herself absently admiring how attractive he looked that night, dressed down in a soft, burgundy sweatshirt with black sleeves and a worn pair of jeans that hugged him nicely. So different from how he usually dressed at the precinct.

She liked seeing him at home.

"It was Sam," he assured her. "Everything fits, it's a good ending."

"Yeah, but without proof it's just a theory. And that family, those kids, they need more than just a theory. They need to know, I need to know." she insisted vehemently, a little too much urgency in her tone. And she knew she had revealed too much, had made a mistake coming here, by the way he looked at her.

His eyes darted to the watch on her wrist, her father's watch. He'd made a quip about it in the car the day before, thinking he had her story somewhat figured out, believing it was her father she had lost. Her cellphone had interrupted her chance at answering him then, interrupted her chance at correcting him.

She sighed and scraped a hand through her short hair. "It was my mother. Not my father."

It sent a strange rush through her bones to see the light change so quickly in his eyes, flashing an electric blue in the dim glow of lamplight his office provided, so thirsty for her story. But the rest of his body remained the same - posture open as he watched her from a chair beside his desk, head tilted slightly to indicate he was listening. And before she could stop it, the words were spilling out, the story he'd so desperately sought tumbling into the space between them.

"We were supposed to go to dinner, my mom, my dad, and I…"

His eyes dimmed as she spoke, growing dark and losing the flare of childlike curiosity that had shone so brightly just seconds before, turning almost the color of storm clouds as she revealed the tragedy that had claimed her life ten years ago. She could already see the story playing out before him through her recounting of the homicide case she knew all too well, as if he had been right there with her to witness the scene himself.

When she uttered what was probably the hardest sentence, that her mother had been stabbed, Kate noticed how his body jerked a little, the urge to move towards her palpable, his need to comfort instinctive. But he didn't. He stayed seated by the desk, giving her space, asking her if it was a robbery and letting her continue like it wasn't so painful, and she appreciated it as she blinked back the tears attempting to congregate in the corners of her eyes.

"The killer was never caught," she finished, staring down at her hands.

"Why do you wear the watch?" he asked softly, and she took a deep breath before diving into another sea of gut wrenching memory.

"My dad took her death hard. He's sober now," she said with her lips momentarily quirking upwards in a sad, but proud smile. "Five years."

He tried to offer her a smile back, but it was forced and weak and heartbroken, which she imagined matched hers pretty well.

"So, this is for the life that I saved," She raised her wrist, touched her index finger to the leather band of the watch. "And this," she continued, forcing the lump rising in her throat to recede as she retrieved the chain from under her shirt. "is for the life that I lost." she finished on a sigh, closing her fingers around her mother's wedding band and letting her eyes rest on the shimmering stone.

The silence that followed was stifling and she tried to joke, to lighten the torturously dark mood that had fallen over them because of her.

"So I guess your Nikki Heat has a backstory now, Castle."

But her attempt at levity fell flat and when she looked up at him, she could immediately read the grief written all over his face. The pain of her loss, her hardships, taking root inside of him as well, and she shook her head as if to dismiss it. She didn't want that. This was not why she came here, not at all.

"Beckett." His response of simply her name was too solemn for her liking and too much, it was all too much, and how could she have been so stupid as to bring this up?

"I think I'm going to go," she mumbled, pointlessly tugging the lapels of her coat together and making her way towards the door. "See you-"

She stuttered to a stop at the gentle closing of his hand around her forearm.

"Kate-"

"What?" she snapped a little too harshly.

"I'm sorry," he murmured rising from his seat to stand beside her, and the sincerity burning in his gaze made her bruised heart swell and ache against her chest. She needed him to stop looking at her like that. "I know it's not enough – not nearly enough – but I'm so sorry."

She bit down hard on her lip - she refused to actually cry in front of him - and flicked her eyes down to the hand still clamped around her arm. He released it immediately, but she didn't move away.

She wasn't as familiar with this Castle - the one who spent his evenings playing laser tag with his daughter and stared at her with overwhelming concern and compassion pouring from his glistening eyes. She only knew the playboy she had seen portrayed in the press, and the man-child she dealt with at work. The Castle she had shared her story with tonight, the man standing next to her, was currently neither of those things. This Castle was closer to the kind of person she had imagined while curled up alone in her bed with his book in her arms and the pain of loss in her heart.

She could grow to like this Castle. If she was being honest, she knew she already did.

Almost experimentally, Kate lifted one hand to his face, slowly skimmed her fingers through the light valley of scruff peppering his jaw, and watched him stiffen in response.

She might not know the real Castle as well as she would have thought, but he also didn't know the real her. Not the version she kept hidden anyway. She found herself wanting to know more, to learn more about him, and perhaps allow him a few more pieces of herself in return. With time, maybe they could both be taught.

"Beckett?" he questioned, voice close to a whisper, eyes wide and searching her face as her thumb swept over his bottom lip.

"Kate," she murmured absentmindedly, stepping closer. "It's Kate."

Her eyes skated down the line of his throat as he swallowed thickly. She was making him nervous and it almost made her laugh, because never would she have thought Richard Castle would be looking at her with a mixture of fear and something between lust and longing while she stood before him with intent in each movement she made.

Before he could back away, she used the hand on his jaw as leverage to pull his hesitant body to hers, and then she kissed him.