Thank you to all who continue reading these, recognition for this prompt goes out to jaelyn2001, thank you so much for sending it in! I hope you all enjoy this.

"I'm sorry I forgot, how do I make it up to you?"

It wasn't like Erin had happily complied in sharing the intimate detail of the date of her birth. Birthday's were something she hadn't celebrated since she learnt that an old cigarette from her mother and a phone call from her father in jail was the extent of the jubilations. And yet one night when inebriation got the better of her, Erin told her partner when her Birthday was.

She could still recall the way his mouth widened as she told him, as though she'd broken off a piece of her soul and handed it to him right there and then. And he smiled as though he'd uncovered some earthly secret about her... But in reality, he'd uncovered exactly that. Apart from Voight, there was no one that Lindsay was in contact with who knew it. And maybe when she lay asleep at night and felt the world slipping away from her, her mind drifted to Jay and how he'd pass her at the precinct sometimes, whispering a soft "only twenty days..." into the air flowing between them, or how he'd hold up seven fingers from his desk when no-one was looking. He seemed more excited than she'd ever been.

To begin with, Erin found it infuriating. She was afraid that someone would interfere and it'd turn into some huge thing. The last thing she wanted was a precinct party thrown where she'd get a huge reminder on all the typical Birthday events she'd missed out on. But as time progressed and something inside her softened and she found little notes taped to her desk counting down the days with a winky face scrawled in the corner, she maybe didn't dread the idea.

They had a tough day with an even tougher case. It was the kind of case where Jay felt everything drawn out of him, both physically and emotionally.

Jay was woken at 7:30am with a violent vibration of his phone on the nightstand. He jumped up quickly and answered it groggily, hearing Antonio's voice too loudly in his ear for a Wednesday morning.

"Got a tip about that drug ring." 'That drug ring' was something the unit had been slowly working on for weeks, keeping it slightly on the backburner until they had enough energy to find something substantial. It looked like they finally had it. "I'm texting you the address now, meet us there." Antonio said.

Jay raced to get there, the early morning sun shining briskly on him as he joined the rest of his unit to get briefed on the situation. As he took his regular space next to his partner, the ever so important detail that had been burning in the back of his mind for weeks had softly and quietly escaped his recollection.

At some point he'd gotten into a brawl with some skeevy cocaine dealer, who was pretty damn adamant he wasn't getting taken into the station, and offered Halstead soe pretty painful blows to the chest. Jay hadn't checked is abdomen, but he was pretty sure it was going to be painted with bruises by morning.

If that wasn't bad enough, he'd been in the interrogation room for most the day with the body beater addict, who had conveniently chosen to keep his lips sealed on his fellow dealers. The drug ring was still ongoing, Jay was struggling to draw any more information out from the only connection they had, and he was thoroughly exhausted.

As he left the interrogation room and walked down the empty corridor, he rubbed his sleep deprived eyes and stopped to lean against the wall. It was hard and supportive against his back, and Jay leaned all his weight into it.

Looking down at his watch, he saw it was nearly nine. He knew Voight well, and what they hadn't uncovered today, their Sergeant would be on their asses twice as hard to uncover tomorrow. The prospect of a 5:30am start the following morning was grueling, but it gave Jay the motivation he needed to get the hell home and into his bed.

As he returned to his desk and grabbed his leather jacket off the back of his chair, he felt Erin looking at him from across the room. She looked tired too, and Jay wondered why she was still there and not across town snuggling into some thick duvet.

He offered a weak smile and she returned it. Erin's eyes lingered on him, as though she was waiting for him to say something. Jay was exhausted though, and as much as he loved spending time with his badass partner, he needed shut-eye.

"I'll see you tomorrow." He said before a long, overdue yawn as he passed Erin's desk, his fingers trailing on the wood slightly.

When he got home, it took all the energy Jay had not to collapse on his bed the second his door was unlocked. But since his tongue needed taste and his stomach was rumbling slightly, he decided to grab a quick snack before hitting the sheets.

Absently, Halstead wandered into the kitchen and threw his keys onto the cool countertop, the slapping of the metal echoing throughout the cold apartment. Swinging the fridge door open, he swiped a beer from the shelf and flicked the top off, not wasting another second before taking a long, slow sip. It burned as it went down but it warmed his insides. He could already feel some of the pain of the day starting to heal.

His back leaned against the counter and he drank some more, only hastily stopping when his eyes drifted to the calendar attached to the fridge.

The date was circled with large coloured ovals, and Jay didn't need to even think why.

He felt like an idiot. No, he felt like a jackass. Erin had shared a part of herself with him, and he knew as the words fell from her lips they certainly weren't easy to throw out to him. And then he just forgot.

Not wanting to waste another second, Jay slid his phone out his back pocket and called her number, holding the mobile as close to his ear as possible.

"I'm an idiot." Jay said, not giving her a chance to even breathe after accepting the call. "I'm sorry."

He heard the sound of her laughing on the other end of the line, but he knew it was hollow. "It's fine, Halstead, honestly."

"No it's not." He urged, his eyes drifting back to the calendar right in front of him. "I'm sorry I forgot, how do I make it up to you?"

"I told you, Birthdays don't mean a thing. We'll get a beer after we crack the case tomorrow... Call it even."

He felt ridiculous. He got sidetracked by a difficult case, and forgot something vital about the closest person to him. He thought back through the day, feeling embarrassed how it didn't click as Voight pulled Lindsay aside during the day, urging her into his office, and how she left with the glint of a smile lingering on her face. Hank Voight hadn't forgotten, but Jay Halstead had.

"Erin-"

"Honestly, Jay, it's late. I told you, it's no big deal, so stop... Feeling bad about it. I'll see you tomorrow, okay?" There was still a light, playfulness to her voice that Jay managed to see through.

Before he could argue anymore, the call ended. He stared at the blank screen for a few more seconds before dropping it on the counter and rubbing his hands over his face, suddenly feeling a lot less tired.

It would be different if Erin regularly celebrated her Birthday, and her sadness was more evident. But Erin hadn't ever had a decent day where she was the sole focus, and that made something inside of Jay ache.

So while his bed was still distantly shouting his name, and bruises on his abdomen were already starting to form, Jay was going to put Erin Lindsay above it all.

She wasn't heartbroken, and she wasn't devastated. She didn't want to admit that she was disappointed, because that would mean that she'd have to acknowledge she was expecting something, and she'd conditioned herself not to do that a long time ago.

But as she lay on her couch and flicked between channels, a tiny part of Erin ached at the fact Jay was in his own apartment halfway across town.

Shaking the thought from her head, Erin shut off the television, holding the tip of the beer to her lips as she turned and looked out the window, the bright Chicago lights flickering.

She didn't know how long she was looking out at the city until her phone buzzed beside her, revealing a text message from her partner.

Come out to the roof. ASAP.

She blinked as she read the words, taking a few seconds to absorb the letters. She tried not to get her hopes up, but again, not for the first time that day, failed.

It was cold, and Erin felt like an idiot for not bringing a jacket. She climbed the steps two at a time, feeling her headspace go fuzzy with each millimeter her body moved. She hugged her bare arms with each step she reached, and felt her body pause as she reached the top.

She stood in front of the door, her heart hammering in her chest until she finally did it. She pushed the door and welcomed a frosty breeze, encircling her body as she stepped onto the rooftop. Then she saw him.

Jay stood by the edge, hands in pockets as Chicago illuminated around him. The wind stole her breath, but that didn't matter. Because seeing Jay somehow gave her all the air she needed.

She walked towards him, trying her best not to grin like an idiot. She failed within seconds, her eyes landing on a plaid blanket laid on the floor, accompanied by a pizza box and a six pack of beers. Her favourite brand.

"Did I mention that I was an idiot?" Jay said, a grin playing out on his lips as she neared him.

"You didn't have to do this." Erin hated that she sounded on the verge of tears. She hated that he did this. She hated that he cared.

He paused before speaking, taking the few extra steps so he was directly in front of Erin. "Of course I did."

They looked at each other for a few seconds with heavy hearts, something pulling them both together. Finally, Erin followed Jay as he slid down on the blanket, suddenly feeling a lot less cold. A beat later, he was pressing a beer into her hand and handing her a slice of pizza, all before she could properly take in the view.

The minutes passed like seconds, the evening sinking into night and any natural light slipping from both their views. But it was comfortable. And safe. And everything Erin wanted from a birthday.

"Oh," Jay said quickly all at once, placing his beer down in front of him and reaching behind his back. He handed his partner a poorly wrapped present, catching her even more so off guard. "Happy Birthday."

Her head fell to the side as she looked at him, a glance of disbelief painted across her face.

"Go on, open it." He urged, bringing both knees to his chest and hooking his arms around them as he watched her.

Slowly, Lindsay began tearing the paper off, exposing a framed, fairly old, newspaper. Initially confusion clouded her mind, her knitted brow conveying this. Her fingers slid across the frame as she glanced over what was in front of her. Wordlessly, Jay pointed out an article on the far right of the front page. It was on the Chicago Police Department. It was the first major case Erin and Jay had cracked together. As partners.

"You... You kept this?" She asked, not daring to look at him.

Jay answered without skipping a beat. "Of course I did."

The wind died out for a second, or maybe it was just the world letting Erin and Jay finally have a second of quietened background noise.

Erin bit down on her lip before she lifted her head again, her fingers still pressed against the glass of the frame. She looked into the bright eyes of her partner and felt something quake. "Thank you."

The edge of his lip twitched at Erin's words, and she found herself focusing so intently on him. The way the wind picked up the edge of his hair, the way is freckles were barely visible in a darkened ambience. She felt the warmth from his skin on hers, and in that moment made one of the most selfish decisions she had in a while.

She leaned forward and enclosed the distance between their lips. She felt him pause in surprise, before feeling his lips soften against the pressure of hers. She was on fire, burning in a safe crackling hearth while the cold wind tried to break through.

She felt the tips of his fingers on her jaw, and as she pulled away slightly he surged forward the extra centimeters. Their lips tugged and collided until a numbness began to set in, but neither wanted to leave that moment.

Finally, after everything left Erin's mind except the taste of her partner's lips, he peeled away from her and rested their foreheads together.

"I'm sorry I forgot." He breathed.

Erin looked up and saw the reflection of city lights in his eyes. She something else too; she saw a future. She saw Birthdays, and lots more of them. "Oh, I think you're forgiven."

And when he let out a grin and a breathy exhale, she kissed him again. And again, and again, and again.