A/N: First fanfic I've written. All mistakes are mine, I don't have a beta.

Disclaimer: Sadly, not mine...

A young girl walked into the precinct, her hair pulled up into a tight ponytail, her face determined. Stepping out of the elevator, she approached a passing detective.

"Excuse me?" she asked politely.

"Yes?"

"Could you tell me where Katherine Beckett is, please?"

"That's her desk over there, if you wait she'll be back from interrogation soon." Detective Ryan said, gesturing at his boss's desk for the girl. As she sat down at the desk, Ryan took off, following a lead on the case.

A few hours later, Ryan returned and found the young brunette still sitting, patiently, at Beckett's desk. After asking her if Beckett had spoken with her, he went running off to the interrogation room.

Kate Beckett was leaving the mirrored room dejectedly, not having gotten any useful information out of the suspect when she saw Ryan heading towards her.

"You got anything?" She asked.

"No, but you got a visitor. She's been here for hours, when I sent her to your desk I didn't think perp'd take this long to crack."

"I got nothing from him. Why don't you meet up with Espo, maybe run the details by Castle again, see if he thinks of anything we might have missed. I'll go talk to this mystery guest." replied Beckett, passing by Ryan, knowing he'd listen to her orders. When she neared her desk and saw the woman, no girl, waiting for her, she paused. This girl, this young brunette, she looked so familiar, but Beckett couldn't place her.

"Hello, I'm Detective Beckett." She offered her hand to the girl, who had stood when she approached the desk.

"Hi, I'm Marissa."

"What brings you here, Marissa?" Beckett could tell the girl was nervous, she was practically shaking her seat. Feeling bad that she had left this potential witness sitting here, waiting, for hours, she tried to make the girl comfortable. "Would you like some coffee?"

"No, thank you. I- uh- I've been, uh, looking for you for a while.." The mystery girl bowed her head, not meeting Beckett's eyes.

"Why's that? Do you have some information for the case?" Prodded the ever-searching detective.

"No..." The younger girl's voiced trailed off. Normally, Beckett would be impatient with this kind of conversation, preferring people to speak to her, not mumble and stutter. But this girl, something was different about her.

"Take your time, sweetie, there's no rush." The girl took in a scraggly breath, trying to force herself to spit out the words.

"I didn't tell you the whole truth before..." She trailed off again, having lost the courage to continue.

"It's ok, why don't you tell me the whole truth now?" Beckett leaned forward as she talked, trying to find some way to comfort the scared girl sitting in front of her. Out of the corner of her eye she saw Espo and Castle getting off the elevator and talking to Ryan.

"My name is Marissa... Marissa Beckett." At those words, Beckett startled, bringing her back to the situation at present, staring at Marissa dumbfound.

"Marissa...Beckett?"

"Yeah. I'm -uh- I'm your sister."

"That's... impossible." Beckett waved away the boys as she continued to stare at the girl in front of her, the girl claiming to be her sister. Standing up, she was about to send the girl away, when Marissa started crying.

"They told me my mother died, that she was killed. But they let it slip that I had a sister, they told me she was saving the world. I've spent months searching through every record and newspaper in New York, trying to find a firefighter, a paramedic, or a cop with the name Beckett. You're the only one." Marissa had finally found her voice, desperately trying to convince the woman standing before her, her only hope at a family.

"My mother died almost 14 years ago. I can't be the right Beckett, I'm sorry, Marissa." Beckett was still standing, staring open-mouthed at the girl beneath her. She didn't want to believe that it was even possible, but how many Beckett's in New York had mother's that were murdered?

"I'm 13 years old, it is possible."

"Who told you about me? Is it possible you misheard them?" She could see the boys out of the corner of her eye, standing in the break room, trying to figure out what was going on.

"My social worker told me. She told me she wasn't supposed to release any of my family's information to me yet, because I'm not 18, and because they hadn't come looking for me yet. But she told me about you, to make me feel better about not having a mother. She wasn't expecting me to search for you this hard." Marissa was beating Beckett, 50 words to 1.

"Your social worker?"

"Yes, my social worker. I've been in the system since I was a baby. My parents gave me up." The possibility that Marissa wasn't lying, that the social worker hadn't been lying, that this whole situation could be reality, it was too much for Beckett.

"I – I have to go make some phone calls. Will you wait here?"

"'Course." answered Marissa, letting her head fall down dejectedly.

Beckett wandered off, letting the boys leave the break room and test the waters near this girl who had upset their partner so much. Castle brought her cocoa, thinking about Alexis ever being in a situation like this, while Espo and Ryan tried to get clues about her conversation with Beckett from her. But Marissa didn't say a word beyond "thank you" to Castle.

Castle left the bull pen, heading in the general direction that he had seen Beckett go earlier. Upon finding her in the halls outside the morgue, he slowed his walk, giving her time to notice him.

"Dad, what are you telling me?" she asked quietly, as though she was afraid to hear the answer. She saw Castle, her forever shadow, standing at the end of the hall, far enough away to give her the privacy he knew she wanted, and yet close enough to show support. Hearing her dad's answer, she crumbled down the wall, letting tears cascade down her cheeks. She didn't care that Castle was present, he had seen her in moments of weakness before. She felt him slide down beside her, silently comforting her with his presence.

"How could you not tell me? How could you lie to me for so long..? How could you leave her there for all these years?" Her questions were coming out wracked with sobs. She was barely listening to the responses coming from her cell phone. She couldn't comprehend any of what her father was saying. Softly, she pressed the 'end' button on the phone, and let her head fall onto Castle's chest. He didn't move, letting her decide how much contact she wanted from him.

They sat together for what felt like hours, Castle moved his arm around Beckett, trying to comfort her more. Finally, Beckett raised her head, staring straight ahead at the wall in front of her, avoiding looking into Castle's eyes.

"He lied, Castle, for 13 years he lied to me." The tears started flowing again, this time with Castle brushing them away, feeling more bold this time around.

"What did he lie about, Beckett?"

"Everything. That girl upstairs, her name is Marissa. She's 13 years old, and she's my sister." Castle gasped, not expecting anything close to that to leave Beckett's mouth. "When she was born, my mother was scared, it was right before she was killed. They decided to put her into the foster system, intending to keep an innocent baby out of it all, intending to get her back after wards. But she died, Dad couldn't bring himself to collect her. He left her there... for so long." The words tumbled out of Beckett's mouth, she needed to get them out from inside her before they exploded within her. Castle tightened the arm that he had around her, reminding her of his presence.

"It'll be okay, Kate."

So, what do you think? Should I continue?