I've marked this as complete, but I feel like I could very easily continue this 'cause the idea is so very interesting.

No Beta Readers were hurt in the making of this.

I might have taken some liberties, but it's based off the following Tumblr prompt:

Anonymous said:

Caskett find a 5-year-old foster kid sat on their swings, crying because no one wants to adopt him. Caskett finally adopt him

–

Lost Boys

–

"Are you okay?"

The little boy startles, rocking back in the swing as his head snaps up quickly before dropping back down again. "S-sorry."

He's too far to tell but Castle thinks he catches sight of red-rimmed eyes and the dark shadow of bruises.

The child's tears stop, the soft sobs ending with a hiccup, and Castle's never seen that before. Never seen a kid that could fall silent like that. Not even his daughter, angel that she was, could stop herself crying on command.

Something is definitely not right, he decides, as the gentle sway of the swing slows to a stop and the boy seems to shrink in on himself, his small frame taking less space than it should.

Fall has nearly turned to winter, the sun nearly set, and it's cold but, even in his t-shirt, the little boy doesn't shiver. He's holding himself unnaturally still, trying to attract the least amount of attention as possible, like a frightened cat huddled in a corner. Even his breathing is silent, the small white-puffs colouring the air are the only sign the boy is more than statue.

Castle approaches slowly, waving at Beckett to wait as she approaches with their dinner, not wanting to startle the kid.

There's not much resemblance, dirty blonde hair and dark eyes, but something about the boy reminds him of his daughter and he can't help himself. Besides, a kid this young shouldn't be alone in the park. It's New York City, for chrissake.

When he's close enough, he kneels down in the grass, heedless of the dirt staining his trousers and the ache in his bad knee.

He definitely sees bruises. Cuts, too. Sharp and angry against the boy's pale skin. Playground fight, he thinks, but some of the bruises have yellowed and the kid's clothes are torn, ragged and a sort of dirty that takes a while to cake in. Realisation sinks like a stone in Castle's gut.

Slowly, Castle pulls off his coat and offers it to the kid. The boy doesn't look up and makes no move towards taking the garment. Castle continues to hold it out anyway.

"My name is Rick," he says. "And that's my girlfriend, Kate."

The boy's eyes flicker over Castle's shoulder but otherwise he doesn't move.

"What's your name, kiddo?"

A beat, and then, barely a whisper, "Ryan."

"Really?"

The boy looks up again, defensive, and Castle smiles at him. "One of our best friends is named Ryan. Well, Kevin Ryan."

Little shoulders droop and he takes that as encouragement. "You should take the coat," he says. "It's getting pretty cold."

No response.

Okay, different tact.

"How old are you, Ryan?"

"Five," he says. "But I'm six next month."

Castle smiles encouragingly. He remembers that age, the way you were always almost something.

"How old are you?" Ryan counters and Castle's grin widens.

"Too old," he says. "Mind if I sit next to you?"

Ryan shakes his head and Castle stands, feeling his bones protest. He walks around behind the boy and he's not surprised by the way the kid stiffens, but the boy doesn't run, and so Castle drapes his coat over the tiny shoulders as he moves to sit on the swing next to him.

"Where are your parents, Ryan?"

The boy's shrug is lost in the folds of his coat. "Gone."

"Do you want help finding them?"

The boy looks at him then, suspicion in his dark eyes.

"It's okay," Castle adds. "My girlfriend, Kate, is a police officer."

"No," he says. "They're gone."

Alexis, when she was this age, loved to spin elaborate tales. Every trip to the park was filled with stories of dragons and princesses and lakes of lava. Nobody was ever just gone.

It's probably better, Castle decides, that they stay gone if the state of the boy is anything to go by.

He hadn't heard her approach, but Beckett's beside him all of a sudden, and he's worried, but the boy doesn't even flinch. Maybe she was right? Maybe she should have approached the kid from the start.

"Kate," Castle says, nodding towards the boy, "this is Ryan. Ryan, this is Kate."

"You're a police officer?" Ryan asks.

"Sure am," Beckett says with a nod. "I'm a detective."

The boy nods, satisfied and it's smart of him, Castle thinks, to double check.

"You look lost," Beckett says, deliberately keeping her tone gentle. "Do you need help finding your way home?"

The boy shakes his head. Defiantly, he adds, "No, I ran away."

"Okay." Beckett just nods and he knows, she sees the bruises too, knows what they mean. "Maybe we can help you find somewhere else to stay."

Ryan narrows his eyes, a look that shouldn't ever have to grace a kid's face twisting his features.

"You know," Castle says, a deliberate air of surprise to his voice. "Kate and I were going to have dinner. A picnic."

"Right," Beckett agrees, "a picnic."

Castle motions to the bag in Beckett's hand. "But, I think I brought too much food."

Beckett nods, understanding. "Too many cookies."

"Way too many cookies," Castle agrees. He turns to Ryan. "Do you think you could help me eat them all?"

It starts off small, stuttering, and it looks strange on the boy's face, but then it grows, settles in, and it feels right. A smile.

–

"Rick, no."

Castle sighs. "I didn't say anything."

"I know."

They're in the observation room, their little runaway sat behind the glass on the other side with a mug of cocoa, a few pens and some paper to draw. He doesn't. He just sits there, feet banging nervously on the metal chair.

He was in the system. Ryan Clark, five years old, reported missing three days ago by his foster parents.

They promised him that he wasn't going back. And he wasn't. Beckett sent the boys out to arrest his foster parents an hour ago.

The problem was, now, that he wasn't going anywhere.

CPS now had three boys to re-home. All of them battered, none of them talking.

"He's not a lost puppy."

Castle shoots her a look. "I know that, Beckett."

"We can't just take him home," Beckett says, but there's no conviction in her voice.

He waits a beat and then, "He's going to end up in a boys home tonight."

"Which is still better than where he was."

"Yes." There's no denying that.

Castle can feel her eyes on him but he can't look away from the boy, still dwarfed by his coat.

"He reminds me of Alexis," Castle confesses.

Genuine confusion colours her tone. "How?"

"I don't know."

They're silent for a while, the tension building between them as they stand together and watch the little lost boy on the other side of the glass.

Beckett finally breaks it with a sigh. "Just for tonight," she says and Castle nods.

"Okay." It won't be, he can feel it, but he won't tell her that.

"I'll see what I can do," she says as she leaves the room.

But she's not the only one with contacts. So will he.