She must hear Nate's screams from the elevator, because she's running to them as soon as they get out of it, her heart jumping inside her chest "What happened?" she asks, instantly reaching for the child in Castle's arms who wraps his arms around her mother's neck sobbing.

"Well, that's what I would like to know!" Castle fires back aggravated, moving past her in a fury, Amy on his right hand.

"What? What do you mean? Castle, why are you mad?" Kate asks turning around to follow him. Kate watches him, running his free hand through his hair while she rocks the toddler in her arms. Castle doesn't respond. "It's okay baby, mommy is here now" she whispers softly to Nate's hear. "What happened? Did he get worse?" she insists, facing Castle.

"Now, you're worried?" Castle says ironically.

"What's that supposed to mean, Rick?" Kate asks, taken back.

"It means exactly what you just heard! You didn't bother come home before, so don't act all worried now! God, Kate, you knew he was sick and you didn't even call!" he accuses, raising his voice.

"We agreed that you would call if he got worse, remember?" she asks him, not happy that he let things get to this point. It's true she didn't' call, but she trusts Castle more than she trusts herself with their kids, he's such a great father. Castle lets out a nervous smile "What? C'mon Castle, you know I had a case!" the detective fights back.

"Yes, I did! I also happen to know you wrapped it two hours ago!" the writer finally tells her, and he can read the shock all over her face, as she steps a little further from him.

The detective takes a long deep breath before whispering "Castle..." reaching out to touch his arm.

"No, Kate!" he shouts, pulling back. Kate trembles. She sees an anger in his eyes that she hasn't seen since that day at her apartment when he begged her to give up on her mother's case and she didn't listen.

"Daddy..." Amy whines, looking up to both her parents.

"Hey baby" Kate acknowledges, shifting Nate to her right arm so that she can use her left hand to caress her daughter's hair. Castle can barely hear Nate crying now, just a few sniffles and hiccups, which tells him that the only thing he needed was having his mother close. He still has his head buried in Kate's neck and not for once he raises it, despite all the shouting around him. Amy leans against her mother's legs, wrapping her arms around them and Kate can tell that she's scared. She doesn't blame her, she had never seen them fight like this before. With all her emotions threatening to take over and fall apart, Beckett makes an effort to pull herself together for her kid's sake and she lowers down to speak to Amy. "Hey sweetie" she calls tenderly, waiting until the girl meets her eyes to continue "I'm sorry that we scared you" she apologizes. Kate fights internally for the best way to handle the situation and after a moment of hesitation she faces Castle "Can we wait until we get home, alone, to talk about this?" she asks as calmly as she can at the moment.

"Talk about what Kate? About the fact that you rather be here in the precinct alone than at home with your family?" Castle replies.

The detective sighs, and without saying a word to him, turns back to her daughter "Honey, do you think you can go and sit at Uncle's Javi's desk for a moment so that I can speak to your daddy?" she asks.

Amy doesn't seem pleased with the request, but nods nevertheless. Kate wishes she could send Nate with her too, but she knows there's no way he'll get away from her now, so she doesn't even try. She waits until Amy is far from them and then approaches Castle "I understand that you're mad, but you have to let me explain" she tells him.

"I don't have to do anything" he disagrees. "You lied. To me. To them. I thought we were passed this" he's not shouting anymore, but he's disappointed, and she can't tell what hurts the most.

"I understand that you're mad" Kate repeats "but you have no right to accuse me of not worrying about our children and you have no right to tell them I don't care about them" she says firmly. Then, noticing that Nate's breathing has even out and that he fell asleep, she handles him to Castle "Here, hold him for a minute, I need to check on Amy" she says, not giving him a chance to talk back.

Castle watches as she walks away, following her steps in silence. He stops a couple steps before Javi's desk, where Kate pulls a chair to sit next to her baby girl.

Amy smiles nervously when she seems her come closer, a coping mechanism that she picked up from her mom.

"Hey stranger" Kate jokes as she sits down "are you okay?" she asks, nudging her legs lightly. Amy shrugs, but doesn't reply or even face her mom. "I'm sorry I didn't go home and I'm sorry we were shouting" Kate starts, her voice trembling "I love you so much, and I'm so glad you're here now, baby" she confesses, finally getting Amy's attention, who tilts her head to find a couple of tears running down her mother's cheeks.

"Mommy, are you crying?" the girl rushes to asks, as she reaches for her face to dry off the tears.

Kate chuckles "I'm just really glad to see you, that's all. I really missed you today" Kate admits, and the next thing she knows Amy is flying to her lap.

"I missed you too, mommy" she offers, pulling her close into a hug.

"I'm so sorry, baby, I'm so so sorry" Kate whispers continuously against her daughter's hair.

Castle watches from a far, touched with the scene but unsure of what to make of Kate's actions. Neither of them speak, and it's Amy, who after while pulls back to speak to Kate "It's okay mommy" she tries to soothe her, caressing her mother's face with her little hands. "Can we go home now, please?" she begs.

The detective chuckles lightly, finally an easy question "Yes baby, let's go" she says raising from the chair and straddling the girl to her hipbone "I can walk mommy" the girl automatically tells her.

"I know" Kate sighs "I just wanted to keep you close to me a little longer" she confesses, ready to put the kid back on the ground.

"Okay mommy, you can carry me" the child gives in, feeling the need in her voice.

Kate smiles and stops by her desk to grab her bag and jacket. She glimpses at Castle, who's already getting the elevator and quickly slips a file into her purse before joining him.

No one speaks during the elevator ride. The detective has her car parked at the door, but she doesn't mention it and follows Castle to his. She can pick it up tomorrow, she's not about to separate from them again. Kate and Castle buckle the kids into their seats and they make the ride home in complete silence too. The detective can't help but glimpse at her partner from time to time, the disappointment written all over his face, and it kills her to once again find herself in that position, but she doesn't dare to say a word.