AN: A short one. I was traveling for two weeks and thought I'd have tome to write, turned out I didn't.

Beckett and the boys had just gathered around the murder board, when the elevator doors opened, spilling Beckett's family out into the bullpen, barely ten minutes after her own arrival at the precinct. The obviously very excited youngest Castle girl was hurrying out in front of their father and Alexis, wanting to get to her mother first.

"Mommy," Ellie shrieked happily, running straight over to Kate and throwing her arms around her mother's legs, while Ryan discretely turned the murder board around so that the girls wouldn't see the crime scene pictures.

"Hellooooo," Ellie grinned up at her mother, dark lashes framing her green eyes before she squealed, loud enough for the whole bullpen to hear. "Surprise!"

Kate couldn't help but laugh at her daughter's adorable antics, forgetting for a moment why she had called her family here in the first place.

"We thought we'd come by and surprise you," Castle said as he stepped up at her side, fortifying the fake explanation he had given the girls earlier and Beckett was grateful that her husband had had the foresight to come up with an excuse for their impromptu visit at the precinct that wouldn't worry the girls more than necessary at this point.

In the meantime Jamie had spotted her favorite uncle and ran over to him with a happy grin on her face when she greeted him, "Hola Uncle Javi."

"Hola Chica," Espo laughed, picking her up and spinning her around. "You're starting to get too big for this, you know." He groaned as he sat her back down, pressing a hand to the small of his back.

"No," Jamie protested, "You're just getting old."

"What?!", Espo gasped. "You take that back."

"Uh-uh," Jamie shook her head, grinning from ear to ear. "You take it back."

Kate watched the exchange with a soft smile even though her mind was already wandering back to the reason her family was here at the precinct on a Saturday morning. She knew Alexis already sensed something was up, throwing her parents questioning looks and so Kate pulled the girl aside to make sure she didn't worry too much.

"This is just a precaution and I'll explain everything later, but for now, could you take your sisters to the break room and keep them occupied for a while? I need to talk to your dad first," Kate explained and Alexis nodded reluctantly, but at least she looked a little less worried.

"Are there still cookies in the jar on the top shelf?", she asked, already hording her sisters toward the break room.

"If L.T. didn't eat them all," Kate gasped in mocked horror as she saw the man in question enter the bullpen.

"I did no such thing, Beckett," L.T. defended himself, picking Ellie up who beamed from ear to ear, having developed a sweet spot for the big man. "Come on, Ellie. I'll show you that your mom is not telling the truth. There are lots of cookies left. I only ate a few. Ten tops."

"Bye Mommy," the girl waved over L.T.'s shoulder and when Alexis and Jamie followed Kate could finally turn her attention to Castle.

"So what's going on, Kate?", he asked once the door closed behind L.T. and the girls. "You have got me worried here."

"I know," Kate sighed, not making him feel any better. "Come on," she pulled him over to the murder board to show him what they got so far.

Half an hour later Beckett and Castle were seated in Montgomery's office while L.T. had taken the girls on a precinct tour, which surely would keep them and every officer and detective they would meet along the way occupied for a while longer.

"Does he realize she's a fictional character, not a real person?", Montgomery asked, scanning the case notes that the team had handed him.

"Obviously he's delusional, but given that Nikki Heat is based on Beckett, maybe he's confusing the two. And Ryan and Esposito showed the victim's family the sketch of our suspect. He did not look familiar," Castle who was now up to speed gave his opinion of the matter.

"And you think Castle and the kids could be in danger too?", her boss asked, looking from Beckett to Castle.

"I'm not sure," Kate looked thoughtful, "the girls are not part of the Nikki Heat universe, but Rick certainly is and we don't really know what we're dealing with here. Who can guarantee he sticks to the books?"

"You're right," Montgomery nodded slowly. "We should keep an open mind and better be safe than sorry. How are we on forensics?"

"C.S.U grabbed about 200 fingerprints, a thousand fibers and 60 odd DNA samples, and that was just from the phone box. They're working them up now… after they clear their backlog," Beckett sighed. Everyone knew that forensics would probably be a dead end.

"Beckett," Ryan came bursting through the door, "Guy on the phone's asking for Detective Heat." All three of them followed him outside to watch Beckett pick up the phone, waiting a second before answering to give Ryan the chance to trace the call.

"Beckett," Kate answered after taking a deep breath to calm her nerves.

"Nikki, did you get the first part of my message?", the same voice she had talk to the day before greeted her.

"Yes, I did."

"Well, the second is at the Central Park carousel," the line was dead and after a moment were everyone seemed to be frozen in place, they sprang into action, shouting orders and grabbing their gear.

"Kate," Castle held her back. "I'm coming with you."

"No, Rick," she shook her head. "I told you -."

"But this is about us, our family. You can expect me to just watch from the sidelines," he insisted and watched her chewing her bottom lip while she contemplated his words.

"Okay, okay," she finally nodded, knowing she didn't have much time to discuss matters with her husband at this moment. "But bring the girls home first. Martha is there, right?" He nodded. "Take L.T. and one of the Unis with you and fill your mother in on everything. Then let L.T. bring you to Central Park and tell the Uni to stay at the loft. Okay?"

"Okay, I got it," he nodded, his expression dead serious before he hurried off to find L.T. and the girls.

"Oh and Rick," she called after him and Castle stopped, turning around. "Tell Alexis we'll explain everything tonight."

He gave her a thumbs up and disappeared around the corner as Kate followed her team members to the elevator.

Beckett and the boys stood next to the dead body of the woman they had just found at the carousel at Central Park, listening carefully to Lanie's findings. Which wasn't much so far, but they already knew they were dealing with the same killer. Lanie confirmed the same M.O. and added the detail that she guessed that their killer was left-handed.

"C.S.U. pull the slugs from the back of the carriage?", Beckett asked, already knowing that there would be a message left for her.

"Yes," Lanie nodded. "There were letters on the slugs. The spell W-I-L-L."

"So he's sending a message. 'Nikki will …'."

"What?", Espo looked at her. "Nikki will what?"

Beckett shrugged and then thanked Lanie, "I don't know."

"So we're dealing with a serial," Ryan stated before his eyes were following his partners' as they watched several black SUV's pulling up to the crime scene, basically confirming Ryan's thought. The FBI wouldn't show up for a simple double murder.

"Looks like the Fed's are claiming jurisdiction over this case," Kate sighed, knowing that the following hours had just become more complicated.

TBC