A/N: Hello all! I got this idea in my head earlier tonight and I have literally gone crazy trying to finish it. At 5.1K words, it's my longest one shot ever. I really hope you guys like this because I worked super hard on it. Special thanks to Amna and Jayne for following along as I read and for the inspiration. Love you guys!

Erin sat on her couch in silence, beer in hand as she thought about the last decade of her life. So much had changed since her first day in intelligence. It had been a while since she has taken her mind this far back into her memory, but recent events have her mind spinning.

Her only daughter had her 6th birthday today, and it lead Erin into a trip down memory lane.

The day they met.

Her first kiss with him.

The first time she slept with him.

Their first breakup.

Getting back together.

Breaking up again.

Giving birth to the baby girl she cherished more than anything.

Another breakup.

And the list goes on, a repetitive and dreadful cycle of fights and makeups.

It all came back in a series of flashbulb memories as she watched her daughter blow out the 6 candles on her Disney themed birthday cake earlier in the day. Since she arrived home, Erin found herself looking back on her life and thinking about how she got to where she is now. Alone on her couch while her daughter spent the rest of the day with her father. The father that Erin Lindsay would forever be in love with. But they weren't meant to be; as proven by the relationship that would crumble every time they tried to glue it back together.

She thought back to the fight that ended it forever, and until now she didn't realize that it had been 3 years since the last time she tasted his lips on hers. She missed him. A lot.

After he ended it she tried so hard to get him to come home, she begged him. She knew she fucked up; but she didn't know that such a tiny bump in the road would ruin their relationship forever.

Their friendship was never the same after that. Their conversations revolved around their daughter, and that was it. That poor girl, Erin's heart broke when she started asking where her daddy was, why he didn't come home anymore. There were times when instead of Erin being a mom, her kid would be the one doing the comforting. Many late nights spent in tears, her daughter would be cuddled into her side, wondering why her mom was so sad and why she couldn't make her feel any better.

A year after their breakup he announced his engagement; and Erin knew that was the end. A part of her was angry at him for not giving her a second chance, but the stronger part knew it was her fault anyway. Their daughter was the flower girl in his wedding, and she couldn't miss seeing her beautiful baby walk down the aisle, so she went. She was gorgeous; the woman that had his last name. Though all three of them knew she would never truly have his whole heart - it belonged to Erin. He settled, and it was her fault.

A sharp knocking on her door brought Erin back into reality. She tried to compose herself as she stood from the couch and made her way to the door. She wouldn't let him see her like this, not after all these years.

She swung open the door to the house they used to share, and was immediately greeted with a front toothless smile. "Hi mama!"

Erin opened the door wider in order for her daughter to zoom past her and into the house. "Hey baby, did you have fun with your dad?"

"Yeah! After the party daddy took me to get ice cream and then we went see uncle Will and he gave me a swimming pool for my barbies!"

"That's great, Court." She said with smile, then she finally looked up to the man who had her heart. " Hey Jay. Do you wanna come in? It's cold out."

Jay awkwardly stood in the doorway with his hands shoved deep in his pockets, and cleared his throat, "Uh, sure."

He followed her into the house and shut the door behind him. It always felt strange being back in that house for him. A part of him had always regretted the night he ended things, but he felt that Erin would never be completely in it after what happened; it got to the point where he felt she wasn't trying anymore, and he could no longer handle being in a one sided relationship. Even he didn't know that would be the last time they broke up. It was just them; they'd break up and be back in each other's arms 2 weeks later. The night Courtney was conceived was actually make up sex, and the duration of Erin's pregnancy was the longest they ever went without some stupid fight tearing them apart. He'd hoped putting a stop to things again would get Erin to have faith in them again. And when she did, he got scared, and didn't let her back in. Then he met Kayla, and she loved him. He liked the attention she gave him. He never intended on marrying her. Until one day he did, and he knew that would he'd never get another chance with the love of his life.

At one point, work got easier for them, and as promised all those years ago, they always had each other's backs. They never talked about their personal lives at work, apart from the occasional chat about their kid. Things were never better outside of work though, there was always tension when either of them picked up or dropped off Courtney.

"How was she today?" Erin asked in curiosity, Courtney was a good kid, and they knew that; but there were days when the young Halstead was quite the handful.

"She was good, I think she liked seeing her cousin."

Erin nodded, but didn't have a response so they stood in an uncomfortable silence in the middle of her living room.

After Courtney finished putting her new toys in her bedroom, she raced down the hallway in search of her parents. "Mama, can daddy stay for dinner? It is my birthday, after all!" She begged.

Erin glanced at Jay, then down at her daughter. "I don't know, baby. You're gonna have to ask him."

"Daddy, please stay for dinner! It's mama's special pancake birthday dinner. Don't you want to eat breakfast for dinner?"

Jay side eyed Erin, making sure it really was okay for her. They were always in agreement when it came to the kid, no matter how much it hurt the two of them. Bending down to her eye level, he gave his daughter the answer she was looking for, "Of course I'll stay for dinner."

Pancakes for dinner on birthdays was one of the few traditions Erin was able to keep with. Jay never missed one of Courtney's birthday dinners. He brought Kayla to Courtney's 4th birthday dinner, and definitely learned from that mistake. Courtney didn't like when other people imposed on their family time; unless it was grandpa Voight.

The three ate their pancakes with casual conversation every once in a while, and with only a few bites left, it was evident that Courtney was starting to get tired out. She was yawning excessively, and at one point she almost dropped her face onto the plate of syrup. "You had a long day, munchkin. You ready for bed?" Jay asked, noticing her droopy eyes.

She gave him a tired nod, and he scooped her up into his arms. While Jay carried her into her bedroom, Erin collected all of the dishes and put them in the sink. Once she was finished, she followed Jay's path into her little girl's room and found her fast asleep, with Jay looking down on her.

Erin crept up next to Jay, and joined him. "She's a pretty great kid, isn't she?"

"That's all you. You're a great mom." He wrapped an arm around her shoulder and immediately, Erin leaned into him.

She smiled, sadly, but didn't make eye contact with him. "I guess you're okay at being a dad, too." She rasped.

He let out a soft laugh, if there was anything he missed about Erin Lindsay, it was her gift of being able to become with the snarkiest of remarks on the spot.

Erin inhaled his scent as he rubbed his hand up and down her upper arm; the action sent shivers down her spine, and suddenly she felt herself turning in his arms and hugging him.

While at first he was shocked, he couldn't help but hug her back. They squeezed each other tight, not knowing when the other would let go, or when they would have enough courage to hug again. He gently tickled her back while she leaned into him with every ounce of her body.

Jay eventually pulled away when he felt a wetness on the center of his shirt. "Why are you crying?" He asked her, moving one of his hands to wipe away the tears.

Her lips turned into a sad smile and she leaned her head into his palm, "I just miss you. I miss us. And it kills me that we'll never get another chance. And I know it's my fault and that if I wasn't so reckless the four of us-"

"Hey, stop." He interrupted, pulling her into another hug. "You know there wasn't anything you could have changed. We did everything right, that pregnancy just wasn't meant to be. If anyone's to blame, it's me. I shouldn't have pushed you so hard to get over it right away. I should have been able to see why it was different for you. I'm the one that gave up on us. Not you; me."

Erin only cried harder into his chest, "You wanted me, and I couldn't give that to you. I'm sorry I wasn't enough." Her arms snaked up his body and wrapped around his neck, and she placed kisses on his shirt covered chest, "I'm so," Kiss. "so," Kiss. "sorry."

Jay stood tense as a rock while she peppered kisses further up his body. His hands trapped on her hips, he could feel himself growing harder with every kiss.

Eventually, Erin's kisses had reached all the way up his neck, and along his jaw, and were now on the corners of his lips. She pulled away slightly to look into his eyes, and she could see the same look of desire and lust that she saw so long ago staring back at her, and she decided to risk it.

She softly captured his lips with hers and when he didn't immediately kiss her back, she moved to pull away; but the moment she tried, his grip tightened on her hips and his mouth moved against hers.

Their tongues danced in sync, as Jay's hands explored the body he hadn't touched in years, stopping when they met her jaw. Things were rapidly becoming heated, and neither could bring themselves to stop. No matter how badly they needed the air, the need for each other was far more intense.

When Jay finally stopped to breathe, he looked down to her, and lifted her into his arms without speaking. They'd missed each other so much, neither realizing how much they really needed one another until this moment; he couldn't bring himself to ruin it.

They didn't break apart until they reached Erin's bedroom. It still looked exactly the way it did before they broke up. Nude walls and the baby blue bedding. Even the photo that was taken of the three of them on the day Courtney was born still sat on the bedside table. While he lay Erin down on the bed and removed his shirt, he wondered if any other man had slept in his bed since he left. Probably, he thought; he had no control over what Erin did, hell, he married someone else.

For a brief moment he thought about Kayla, and the consequences this was going to bring to his marriage, but Erin Lindsay was lying half naked in front of him, and his brain was foggy. In this moment, Erin was what he needed, and he was what she needed, and that was all that mattered.

He ground his hips against hers as their mouths matted together. The two of them were cherishing every second, and didn't want to rush this. He parted their lips, and with one hand pinned both of Erin's above her head. He used the other to unbutton her jeans and slid his hand underneath the denim. Hey toyed with her clit, causing a moan to slip from Erin's mouth into his, before thrusting two fingers deep into her core. His lips traveled from her mouth to her neck, to her collarbone, then back up in the opposite direction. As his fingers thrust harder into her, he released her wrists from above her and tangled his free hand in her hair.

Her eyes were closed when he looked down on her, and he promptly removed his fingers, causing a slight gasp to be released from her lips. Hovering over her, he kicked off his shoes and pants, and then removed hers before replacing his lips on her milky skin.

Erin's hands found their way into Jay's hair as his head went deeper along her body, and he began sucking and licking her clit. She let out a moan of pleasure as his tongue became readjusted to the familiar lips. And groaned when he suddenly stopped.

Before she had a chance to ask for more, her lips were attached to his once again. They panted as she flipped them over and started to rub herself against his hard cock. She teased him a while longer, and when she finally slid onto him, a wave of immediate pleasure hit them both. Erin was only in control for seconds before Jay rolled them back into their original position. He thrust deep into her, hungry for more; trying to make up for all the lost time in recent years.

As they came, their screams were muffled into one another's mouths, desperately trying not to awaken the 6 year old that was peacefully asleep two doors down.

Rolling off her, Jay pulled the comforter over their naked bodies and pulled Erin into his side. He traced random patterns up and down her arm, while she did the same on his chest. Their breathing was heavy, and for the first time in 3 years, the silence was comfortable.

They knew what was going to happen when the silence broke. Jay would go home to his wife and Erin would probably cry herself to sleep to a cold and empty bed. It was inevitable, and Erin was now officially the other woman, but for some reason, she didn't feel bad about it. She only felt bad about the fact that he'd be going home Kayla instead of herself.

They rest in silence for a long while, it was going on 11 when Jay finally climbed out of the bed. "I should go."

Erin got up as well and found something to sleep in, "Yeah, you're right. I'll see you tomorrow." Her voice croaked, and she turned away from him so he couldn't see the tears pricking her eyes.

"Erin." He called, but she didn't turn around, which forced him to gently tug on her bicep. She refused to look at him still. "Er, look at me." When she met his eyes, the unfallen tears began to stream down her face. He repeated his gesture from earlier in the night, and wiped the tears from her face. "I love you, you know that? I always will."

She nodded her head and he gave her a quick kiss goodbye. Neither knew where they stood.

The following morning, work felt like the day Jay told the unit about his engagement to Kayla. They didn't speak all day, Voight could sense something was off and partnered Erin up with Antonio, so they didn't even need to speak about work related topics.

It was nearing the end of the work day when Jay approached Erin in the break room. So many important conversations have been held in the Intelligence Unit break room, it was sort of their spot. She prepped him a cup of coffee the way she knew he likes it and handed it to him when he was in arm's reach. "Last night..." He started.

"Save it, I know what you're going to say." She interrupted. After pausing and taking a sip of coffee, she added "And you're probably right. It was irresponsible and shouldn't have happened." She didn't wait for a response, and he let her walk away for the thousandth time in the last decade.

Later that night, after Courtney was in bed, Erin found herself in the same position as the previous night. Only this time, the memories were fresh in her mind. She could still feel his lips on her skin, and his scent still lingered in her bed. She walked into her daughter's room to make sure she had all of her stuff packed for when she left for her father's in the morning.

Sitting in her daughter's bedroom she heard a faint knock coming from the front door. She got up from her respective spot on the floor and moved to answer the door. As soon as she pulled the door open, her mouth was attacked by the man that was taking over her thoughts. He guided to her to the bedroom, and every time she tried to protest, he silenced her with kisses. "You didn't let me finish earlier. If you had, I could have told you that last night wasn't a mistake." He said before reattaching their lips.

He stayed the night that night; Kayla had left that night for a business trip, so he didn't need to go home. And they planned for him to wake up early the next morning so Courtney wouldn't know he slept over.

They continued sneaking around for several months after that. Surprisingly enough, it was the most successful they had been at keeping a steady relationship between them since Erin was pregnant. Their partnership at work improved by miles, and finally, after all these years things were normal again for them. There were times where they thought someone was catching on, and they'd "cool it" as they did all those years ago, but they couldn't keep their hands off each other. It was like they back in the beginning, before all of the drama happened. It was simple.

It was official, after a solid seven year relationship, Ruzek and Burgess were finally tying the knot. Their engagement party was tonight and all of intelligence was going to be in attendance. Save(except?) Voight, who offered to watch Courtney for the night. He'd much rather spend a quiet evening at home with his silly granddaughter than with a bunch of silly adults who had way too much alcohol in their systems.

It hurt Erin when she say Jay walk through the doors of the lounge with Kayla's arm looped through his. She quickly downed her glass of whiskey and found someone to mingle with in order to avoid him. Nearing the end of the night, she was pretty wasted. While she managed to avoid Jay and Kayla for most of the night, alcohol became her best friend. It barely phased her when Kim asked her to be a bridesmaid in her wedding. "You alright?" Kim had asked the spaced out Erin. Her gaze was focused on the 'happy' couple dancing several feet away from them.

"Sorry what?"

"I asked if you're okay. You seem a little, off." Burgess picked her words carefully, she didn't want to be on the receiving end of an Erin Lindsay outburst at her own party.

Clearing her throat and shifting her focus to the woman in front of her, Erin responded with, "Yeah, I'm good. I'm gonna run to the restroom." She stumbled out of the bar stool she was seated in and drunkenly made her way towards the bathroom.

Jay saw Erin shuffle towards the bathroom and excused himself from his wife to go and check on her. He followed her through the crowd and straight into the women's restroom. "What do you want?" She asked, her back facing him. She knew he was going to follow her, but that didn't mean she wanted to talk to him.

"You're drunk." He said.

"What's it to you?" Erin questioned, finally turning to face him.

"What's that supposed to mean?"

"C'mon Jay you know exactly what I mean." She said, a mix of anger and sadness in her voice. "Do you think it's easy for me to see you with her? Our best friends' engagement party and you bring her. I can't dance with you; or kiss you." By this point, tears were streaming down her face.

"Erin, she's my wife. I-"

"I know what she is to you Jay. I was there. I watched you say your vows while looking directly at me. I've seen you tell her you love her, but it's not there; it isn't in your eyes. I know you, Jay Halstead. She may be your wife, but that doesn't change the fact that it kills me to see you with her." She tried to leave the bathroom, but he blocked her path to the door. "Let me go." She begged.

"No."

"Let me go." Erin said again, more sternly, taking a step closer to him.

"Erin." He said softly. When she didn't answer, he took another step towards her, practically erasing the distance between them.

Erin regretted looking up the very moment her eyes made contact with his. Without thinking, she kissed him hungrily. Each one of their kisses were tender and sweet. Clothes were shed and soon enough he was inside her. It was quick, but it felt like the world was turning in slow motion. Since they started their 'fling' the sex was usually rushed and messy. And while this time was just as rushed, it felt more meaningful. It was like they had finally released all of the pent of feelings they had put away. Before, it was more about the sex; this time they gave it their all.

Once finished, a not as drunk searched the spacious bathroom for her discarded panties. "Jay, I was wearing panties. Do you see them anywhere?" She asked, flustered.

Jay looked around, but didn't see them and shook his head. "Forget about 'em. Going commando is sexy." He smirked, and she scoffed in return. "Kidding." He reassured, fixing his tie. "Do you want a ride home?" He offered after a few seconds of looking for her still missing underwear.

"You sure that's a good idea?" She questioned with a raised eyebrow.

"It's better than you driving, how much have you had to drink?"

She shook her head in annoyance, "Don't start this whole 'protective boyfriend' crap on me Jay. I get it, I'm a good lay. You don't need to pretend that you care to spare my feelings." She was putting up her walls again. It was a defense mechanism, and she felt like she was losing him all over again. If she pushed him away, she'd spare herself another broken heart.

Jay tilted his head to the side and scoffed, "You and I both know that's not true. I'm driving you home. Give me your keys." They walked out of the bathroom together, Erin leaning on Jay for support, she still couldn't manage to walk in a straight line after the amount of alcohol she consumed.

Jay caught Kayla on his way out, and handed her the keys to his car, "This one is sick, I'm gonna drive her to her place. I'll see you at home." They thanked Kim and Adam for inviting them, and walked out of the lounge. Kayla staring them down like a hawk.

He hauled Erin into the back seat of the vehicle and climbed into the driver's seat. She fell asleep on the way home, and he had a difficult time getting her into the house, as she could barely stand on her own two feet.

He carried her into her room and removed her shoes, then her dress and found something in her dresser for her to sleep in. After slipping the oversized t-shirt over her arms and head he pulled the covers back and tucked her in. He bent down to kiss her forehead, but instead she groggily captured his lips with hers.

On his way out, he heard her rasp his name, "What is it, gorgeous?" He asked sincerely.

"I hate you." The words exited her mouth like venom. He knew she didn't mean them, but it didn't make them hurt any less. She was upset and jealous and had a rough night. He didn't blame her at all. Besides, he knew she wasn't going to remember it the morning, so he brushed it off.

Erin woke up the next morning with an excruciating headache. The last thing she remembered from the night before was talking, or arguing, with Jay in the bathroom. The rest of the night was a blank.

Dragging herself out of bed, she put on a pot of coffee and took a quick shower. She had to be at work in less than an hour, and it was killing her not knowing what had happened with Jay.

It was a slow morning for Intelligence, and everyone was glad, most of them suffering from hangovers from the party.

Around noon, Jay asked Erin if she wanted to grab a bite for lunch, and she gratefully accepted. Partially because she wanted to know about last night, and partially because he always pays. As they walked down the stairs of Intelligence, they were met halfway with an annoyed looking Platt. "You've got company, Halstead."

Jay peeked over her shoulder and saw his wife standing at the front desk. He was upset because he was looking forward to going to lunch with Erin and discussing their current predicament. Kayla's face of joy turned green watching her husband descend the stairs with Erin. "Kayla, what are you doing here?" Jay asked timidly.

Kayla tried to hide the jealousy that had washed over her face in a matter of seconds, "I just thought I'd drop by and take my husband out for some lunch." She answered, with extra enunciation on the word 'husband', making eyes at Erin.

Jay faked a smile, "Thanks, I appreciate that. But you should have called; I already have plans with Erin."

Erin tried to intervene, "No, Jay. Go, I mean after all; she is your wife." Amongst the short conversation between Jay and Kayla, she remembered snippets of their bathroom argument.

"You're right, I am his wife." Kayla spoke proudly, "Not just the whore he's been sleeping with." She raised her voice as she neared the end of sentence, and it caused the entire precinct to shut down. The room was so quiet you'd be able to hear a pin drop.

Jay and Erin shared a look, and the it would be an understatement to say she was upset. "Kayla, not here. Let's go upstairs." He attempted to guide her away from the ever growing crowd but she roughly pulled her arm out of his grasp.

"Why Jay? You don't want all your friends to know that you're a cheating scumbag?"

Jay sucked in a breath and carefully worded his next sentence, "No, but I'd rather not have my entire district know that my wife has been cheating on me for most of our marriage with various men in several different cities, so if you'd follow me upstairs that'd be great." He made eye contact with Erin before he rushed back up the stairs to intelligence, Kayla following closely behind, completely red in the face.

"Alright back to work everybody." Platt called out from behind her desk.

Erin stood frozen in the center of the district. Jay never once told her about Kayla's infidelity, and it was a shock to have to find out with several uniforms and detectives as witnesses.

Kayla stormed out of the 21st twenty minutes later, and it was then that Erin finally decided to walk back upstairs. She found Jay sitting alone in the break room, clearly frustrated and disoriented from his fight with Kayla. She made her way towards him and sat at the table across from him, "Why didn't you tell me?"

Jay looked up and into her eyes, "I was ashamed. I've known the entire time. I guess I felt that if I couldn't make my marriage work with her, I wouldn't be able to make it work with anyone. And I know this is hypocritical of me, but things were going so great for you and I lately. I didn't want to ruin it by popping our bubble." There was a sense of vulnerability in his eyes that Erin's never seen before. In the entire length of time they'd known each other, never once has she seen this look before.

She absentmindedly took his hands in hers, words didn't need to be spoken, the gesture was enough.

Jay filed for divorce that day and moved out a week later, moving back home to Erin and Courtney - his girls. Though for several months, he and Erin technically slept in separate bedrooms, with the occasional 'sleepover' when needed. They decided to start their relationship from scratch, and even though they already had a child together, they didn't want to rush things. This time around, they wanted to things right.

"Happy birthday dear Courtney, happy birthday to you!" The entire room sang before Courtney blew out the big '7' shaped candle on her cake.

"Happy birthday baby." Erin said as she kissed her daughter's temple.

"Let me get a picture!" A very pregnant Kim Ruzek (nee Burgess) called from the opposite end of the table. Jay, Erin, and Courtney were all huddled into each other, and Kim couldn't pass up this photo op!

They ended the night watching one of Courtney's favorite movies with plates of pancakes on their laps. And as Erin watched Jay carry their daughter to her room, she thought about how much had changed in just a short 365 days.

They slept together.

Their scandalous affair.

The "I hate you" she found out about months after it was said.

His divorce.

His coming home.

Their engagement.

For the first time in Erin Lindsay's life, she was happy. She had a family that most people can only dream of. She was happy, and so was he.

"The girl saw the comet and suddenly her life had meaning."

A/N 2: Title (courtesy of Jayne) was inspired by One Tree Hill, and I took several concepts of this fic from various OTPs. I'm not sure if anyone picked up on the cause of Jay and Erin's original break up. If you think you did, let me know! I kinda left it a secret because I might turn this into a series of one shots in relation to this original one. Let me know if you'd like me to, because I really like the Linstead I have here. If that does happen, the one shots can be requested, and it could be past or future, whatever you decide. Again, I hope you guys liked this story, I enjoyed writing it! Don't forget to leave me a review and let me know what your thoughts are! :)