Jay hung up his phone and slammed it down on his desk much louder than he'd anticipated, earning concerned looks from everyone in the unit. He mumbled an apology as he stood up and made his way over to Voight's office, knocking twice on the door.

Erin had no idea what was wrong with her partner and tried to listen in on his hushed conversation with their sergeant but couldn't make out what was being said. She kept her eyes fixed on Voight's door until Halstead exited, clearly in a hurry. He grabbed his leather jacket off his chair and waved goodbye to his team as he ran out of the bullpen and down the stairs out of the district. The rest of the team sat at their desks in shock, some of their mouths hanging open, unsure of what had just happened.

"What the hell?" Ruzek broke the silence and everyone turned their attention to Erin.

"Don't look at me!" Erin glared at her co-workers, just as confused as the rest of them. She stood up and barged into Hank's office, slamming the door behind her in frustration.

"Hank…" she started, her frustration and anger quickly turning to worry. "What just happened?"

"That's something you're going to have to ask your partner. Go, take the rest of the day." Her father figure shooed her out the door, offering no further explanation as he resumed the phone call she had interrupted.

Erin walked out of Hank's office to expectant faces from each member of the team, each silently begging her to let them in on what was going on, but she just shook her head. "I have no idea," she mumbled, grabbing her own jacket off of her chair and running out of the precinct as Jay had done minutes before.

She got into the 300 and reached into her back pocket for her phone, hitting her #1 speed dial. "Come on Jay, pick up your damn phone," she muttered as she backed out of her parking spot and began the familiar route to her partner's apartment. Of course, he didn't answer and she flipped the sirens on and broke every possible traffic law on her way to his building. When she finally reached her destination, she threw her car in park and sprinted inside the building, taking the stairs two at a time.

Jay groaned when he heard an insistent knocking on his door.

"Halstead! If you don't let me in in 10 seconds, I swear to God there will be a bullet through this lock!" His partner's voice rang out and he couldn't help but smile as he made his way over to his door.

"Er-" He began as he swung the door open to reveal his very pissed off, very confused partner.

"What the hell? Why did you just storm out of the precinct like that? And who were you talking to on the phone?" she cut him off.

"It was my dad." He said simply, a statement that basically answered all of his partner's questions.

"Oh," Erin's voice became softer and concern clouded her eyes. "Is everything okay? Are you okay?"

Jay opened the door wider and motioned for her to come inside. She entered his apartment and walked over to his couch, staring at him intently as she sat down. He sat next to her and let out a deep sigh before beginning.

"His latest girlfriend left him," he started. Erin gave him a confused look, not sure why that would bother Jay, but stayed silent to let him continue. "And she left him with full custody of their four year old daughter. But my dad just accepted a short-term job offer at a hospital in Bolivia and he can't take her with him... and he called me asking me to take over custody of her until he gets back to the states…"

Erin's eyes widened and she reached for his hand, squeezing it reassuringly. "What did you say?" she asked quietly.

"He sprung it on me so fast. That was the first time I've spoken to him in over two years. But I can't let him take a four year old to Bolivia where he'll be working 70 hours a week. He wasn't even a good father when he was a stay-at-home dad in America. So I said yes, out of panic, but then I realized that I can't take care of a kid. I've never even met her, Erin…" he let go of Erin's hand and leaned forward, resting his elbows on his knees and burying his head in his hands.

"Hey," she whispered, moving closer to him and reaching up to trace patterns on his back with her fingertips in an attempt to comfort him. "Damn you and your morals, Halstead. But you've got a whole team behind you – Voight, Olinsky, Antonio; they're pretty damn good at taking care of kids. And you've got me. It may not be much, but I've always got your back."

Jay turned his head in his hands to look at his partner. "That's what means the most. Come here." He sat up and pulled her into a hug, resting his chin on top of her head and squeezing her tight. "Thank you, Er. I'm sorry for storming out like that."

"I understand." She pulled out of his embrace to look at him. "So what now?"

"I have to pick her up from the airport in an hour… my dad said he's sending her with some clothes and essentials but that's it… Erin how do I shop for a 4 year old girl?" Jay began to panic again.

"Okay, here's what we're gonna do – you're going to calm down, then we're going to get her from the airport and we will talk to her and find out everything she likes and what she needs, then we'll take her shopping. One step at a time, partner." She smiled reassuringly, trying to hide the doubt enveloping her mind.

Jay just stared at his partner, wondering how exactly she had the power to make the world stop spinning and calm him down even when everything around him seemed to be crumbling. "Thank you," he repeated.

"That's why you have back up. Now let's go in case we hit traffic." Erin stood from the couch then reached for his hand and pulled him up too. "By the way, I'm driving." She looked back at him with a smile as they made their way out the door.

xoxoxoxoxoxo

"Jay, stop pacing and come sit down." Erin begged.

Jay sighed and sat in the seat beside Erin in the O'Hare arrivals terminal, now bouncing his knees up and down to channel his nervous energy. Erin was about to make a sassy remark about that too when her attention was captured by a little girl with curly brown hair and bright blue eyes making her way to them. She had to be a Halstead. Erin squeezed Jay's shoulder reassuringly as he stood up and made his way towards the young girl and the older woman accompanying her.

"Hey, I'm Jay…" he said quietly, squatting down so he was eye level with the little girl who looked as nervous as he did.

The annoyed-looking older woman interrupted his introduction. "I was her nanny out in California, but now that you're here I am officially free. Have fun." She dropped a backpack in Jay's lap and practically ran back through the airport without so much as even a goodbye, showing just how much she had cared.

"I'm Brielle…" the younger Halstead whispered with a shaky voice, watching her nanny disappear into the distance.

"It's very nice to meet you," Jay told her, unsure of where to go from here. He glanced back to Erin, who was watching him intently, and silently begged her to come help him.

Erin stood up from the chair and made her way towards Jay and his little sister, both of whom looked terrified. She crouched down next to Jay and smiled at the young girl. "Hi Brielle, I'm Erin. I'm your brother's partner at work. How are you?" she asked gently.

"You're pretty," Brielle whispered, her voice still shaking.

"Thank you sweetheart, so are you." Erin reached out and brushed one of Brielle's curls out of her face. "Why don't we go pick up your suitcase then we can go get some food?" she suggested.

Brielle nodded and Erin and Jay stood up from the floor and began to make their way towards baggage claim. Brielle reached out and grabbed Erin's hand when they began to walk and the sight caused Jay's heart to swell. Luckily, Brielle's luggage was the first bag on the carousel and they were able to leave the airport quickly. Jay helped Brielle with her seatbelt in the back before he climbed into the passenger seat.

"You okay?" Erin asked quietly once he got in. Jay just nodded, so she turned around to face Brielle. "What do you want to eat?" she asked softly.

The little girl just shrugged, so Erin continued. "Here in Chicago we have reallllly good food. What do you like? Chicken tenders? Hot dogs? Pizza? Cheeseburgers? Pancakes? Ice cream?"

Brielle's face lit up. "Ice cream? But it's dinner time!"

"But we're celebrating! Do you want ice cream for dinner?" Erin asked, mirroring Brielle's smile.

Brielle eagerly nodded. "Yes please!" Her voice was strong, no longer shaking, and she had finally stopped whispering.

"Well then ice cream it is. Right, Jay?" Erin turned back to her partner, who was staring at her in amazement.

"Right." He choked out, laying a hand over Erin's hand on the gearshift and squeezing it as a silent thank you.

xoxoxoxoxoxo

The three sat at a table in the back of Coldstone as Brielle chowed down on her vanilla ice cream with gummy bears.

"So, Brielle, tell me about yourself…" Jay said nervously, still unsure of how Erin was communicating with the young girl so easily.

Brielle shrugged. "My name is Brielle Anna Halstead but mommy and daddy call me Brie. I'm four years old and I go to pre-school and I like princesses and the color pink." She said simply, but neither detective missed the way her voice began to shake again when speaking to her brother.

"Oh my gosh, Brie, I love princesses too!" Erin smiled.

"Who's your favorite?" the younger girl asked, her voice strong again.

"Definitely Ariel. I want to be a mermaid!" Erin declared, earning a laugh from Jay. "How about you?"

"I like Rapunzel. Tangled is my favorite movie." Brielle shared before stifling a yawn.

"Are you tired?" Jay asked his little sister, who nodded.

"You've had a long day, huh?" Erin asked.

Brielle nodded again. "Daddy picked me up early from pre-school today and told me that I had to come live in Chicago because he was going away to help save people. I didn't sleep on the airplane because I was too scared."

Both Erin and Jay's hearts broke for the young girl in front of them. "Daddy just told you that you were moving today?" Erin asked.

"Yeah." Brielle said quietly, yawning again.

Jay felt anger bubbling inside of him, unsure about how his father could do this to his poor daughter, but he wasn't surprised. "Let's get you home then. We can go shopping tomorrow."

xoxoxoxoxoxo

Brielle fell asleep in the car on the way back to Jay's building and Jay carried her into his apartment and laid her down in the spare bedroom. He made his way back out to his living room, where Erin sat on his couch sorting through Brielle's suitcase.

"She hates me." He declared.

Erin looked up at her partner and shook her head. "Jay, she doesn't hate you. She's just scared, her entire life just changed. A few hours ago she was having story time at preschool and suddenly she's been dropped in Chicago with a stranger." She said softly.

"But she warmed up to you so easily. She won't even talk to me without whispering or shaking."

"It's a girl thing. She's just tired and confused, I promise. I bet everything will be better in the morning. Jay, she's going to be so thankful for you."

Jay nodded. "Thanks, Er. I don't know what I would've done without you today."

Erin smiled as she stood up. "I'm gonna get going. I organized most of her stuff; your dad packed her a lot. I don't think you'll need to do too much shopping but let me know if you need anything, okay?"

Jay walked towards his partner and enveloped her in a hug. He whispered one final thank you into her hair, then watched her as she pulled away and walked out of his door. He sighed as he dropped down onto his couch and reflected on how much his life had changed in one day. As always, his only constant was Erin. He was so thankful that she was his best friend, but he wanted so much more. He groaned aloud thinking of Voight's stupid no in-house romance policy, before silently scolding himself and telling him to take his mind off Erin because he had to focus on taking care of the child sleeping in the next room over.

He must have dozed off on the couch at some point, because at 1:34 a.m. he was woken up by stifled sobs coming from the guest room. He shot up and ran into the room to find a crying Brielle curled up in the corner of the bed.

"Hey, Brie..." he said softly. "It's me, Jay. You're in Chicago with me, remember?"

Brielle turned her head to look at him but the sobs continued. "Rin-" she choked out between cries, and Jay sighed, not knowing what was wrong but knowing exactly who she was asking for.

"Why don't you come watch TV on the couch with me and we can call Erin on the phone?" he suggested.

The little girl shook her head and began to cry harder, sending Jay into a panic. He pulled his phone out of his back pocket and dialed his partner's number.