I wrote this quick oneshot from a prompt posted on a cute TUMBLR blog called ImagineMorganAndPrentiss (to access it, write the name followed by 'dot' tumblr 'dot' com). I'll give you the post at the end of the story.

Remember, Emily used to work in Chicago before she joined the BAU….

The lights were dim and soft jazz music played making the room feel cosy and sleepy. David Rossi took the last swig of the golden brown liquid from the whisky glass and placed it on the bar as he stood up off his stool.

"Well that's me done." He said, placing a soft hand on Derek's shoulder. "I'll see you two in the morning."

"See you Rossi." Emily smiled, her fingers resting around the rim of her glass, still half full.

"At least you made it past midnight." Derek chuckled, "Better than the others. Everyone is such a lightweight."

"Hey, I'd drink you two under the table if I wanted. Experience always wins over youth Derek. You should know that by now." The older profiler winked.

"Yeah yeah. Next time Rossi. Next time." Derek challenged, Rossi then turning on his heels, holding his hand up with a wave as he walked away from the two Agents left propping up the hotel bar in state of Wyoming.

"I can't wait to get home tomorrow." Emily sighed, "This case took way too long."

"I know, but I don't think anyone is as keen to get out of here more than Rossi." Derek chuckled.

"Oh yes. His old fling from the precinct." She smiled.

"He seems to have one of those wherever he goes. I can't believe he didn't remember her name." Derek said, shaking his head, "Rossi looked like he wanted the ground to open up and swallow him."

"What about that poor woman?" Emily bargained. "I'd of been so embarrassed."

"Well I suppose Rossi has been around the block a few times. But to not remember her at all."

"Oh like you remember the name of every woman you've ever slept with Derek Morgan." She snarked, rolling her eyes.

The dark Agent's mouth hung open and he raised a brow towards her, "You don't have a very high opinion of me do you?"

"Derek." She began as a matter of fact, "If someone pointed you out to most women at Quantico and asked who you were, the most common answer would be 'Derek the player Morgan'."

"Oh that hurts." He mocked, placing a hand to his chest, "But contrary to what you might think, I really haven't had many one night stands. I do like to do the whole dating thing first."

"Really?" She said with a raised brow, unconvinced.

"Yes really."

"So it's never happened to you then? Woken up next to someone and not known their name?"

He pursed his lips and glanced sidewards and upwards.

"See, I knew it." She smiled satisfied, "So, tell me then."

"I'll tell you mine if you tell me yours."

"Who says I have a story?" She defended.

"I know Emily Prentiss is a bit of a wild child. Or at least used to be."

"Oh right. You think so eh? Well, you go first then."

"I will, but this better not be a trick and when I've finished you say you've got nothing."

"Well, you're gonna have to take the gamble aren't you?" She nodded, attempting to remain serious.

"I guess. But I reckon it'll be worth it."

"We'll see." She smirked.

"Ok. So there is this one woman that I don't know the name of and it's bugged me for a long time."

He paused, taking a mouthful of beer, "I don't suppose you know Bennett's Bar from when you worked in Chicago? It's on Lincoln Avenue. "

"Actually I do." She half chuckled, "Popular with local law enforcement. I mostly tried to avoid it."

"Hmm." He frowned at her last statement and decided he would probe that later, "Anyway, it was my last day working for Chicago PD before I left to come to Quantico. My buddies wanted to take me for a leaving drink so they took me there. Got me absolutely wasted. Gave me shots, spiked my beer with spirits.… The lot."

Emily laughed silently taking a sip of her bourbon. "I've never seen you wasted."

He shook his head, leaning in closer to her, "And nor will you…. ever." He stressed, "I have no intention of being in that state ever again."

"So what happened?"

"The music was playing. No pounding, and the room was spinning. I just had to get out of there. I was talking to this girl at the bar and I remember her holding my hand and leading me outside. We were basically sneaking out like a couple of kids. After that, I don't remember much other than waking up the next morning in my apartment and she was gone."

"How do you know she was even there?"

He smirked, looking downward as if his mind was right back there, "Oh, I know she had been there. I remember parts of the night. It was pretty blurry but I know I had a real good time." He winked.

She rolled her eyes with a small smile dancing on her lips. "What do you remember then?"

He licked the liquor that lingered on his lips then bit down on the bottom one, attempting to subdue a contemplative smirk. "I remember her voice. It was really husky. Incredibly sexy. Drove me totally wild when she whispered in my ear." He said, taking a long swig of his beer as he remembered, "She had long dark hair that was so soft it was like silk, and… she did this thing…." He continued, glancing back up to Emily with his brow raised.

She scrunched her nose and looked at him cautiously, "Do I want know what this thing is?" She murmured.

"It was nothing really kinky." He laughed, shaking his head a little, "It was just she did this thing with her tongue on my ear when she whispered in it and…" He paused, still looking down as he reminisced, not noticing Emily's eyes suddenly boring into him, "Well." He continued, "I don't know why, but I know it blew me away. Like seriously, I can still kinda feel it."

Emily's breath suddenly caught in her throat and hearing her small gasp, he looked back up to her, "I'm grossing you out aren't I?" He asked with a smile.

She cleared her throat and then pressed her lips together, "No." She shook her head, "What else do you remember?" She asked, the words falling out of her mouth more eagerly than she would have liked.

"I remember her tattoo."

"Tattoo?" She felt her hands go clammy.

"Yeah." His brow furrowed and he pursed his lips as he recalled, "It was a small black and white butterfly above her hip." He said, lightly placing his hand on his own side, just where the ink work would have been on her, "I remember paying that a lot of attention."

The brunette sat upright, releasing some of the tension from her chest, "You sound like you remember a lot." She nervously chuckled.

He shrugged and let out a long sigh, "Not really. That's it. I don't even remember her face." He said sadly, "The only clue she left me was her bra."

Emily suddenly took a sharp intake of breath and choked a little on the remnants of the bourbon, "Oh god." She uttered, placing her hands to her mouth.

Derek's face scrunched up in confusion. "What's up?"

She exhaled, "Nothing." She whispered from behind her palms.

"So then." Derek began, a playful smile forming on his lips, "Your turn."

She stared at him blankly.

"Oh no. You're not getting away with this Emily Prentiss." He told her, shaking his head, "There's no way you don't have a story to tell."

She lowered her hands into her lap and bit her bottom lip anxiously, "You already know mine." She breathed.

"What? No I don't. You haven't told me anything before."

She swallowed and took a long sip of her drink before turning her gaze back to him, "The bra…. That your mystery woman left behind." She paused.

"Yeah?" He questioned in confusion.

"It was red lace with black stitching right?"

"Yeah." He nodded, "But how did you…."

His eyes widened in realisation and the two profilers remained locked into each other's stare for what felt like an eternity.

Eventually, Derek traced his tongue quickly along his lips to moisten them due to the dryness that had suddenly formed before breaking the silence. "You mean me and you…" He nodded towards her, waving a hand too and fro between their bodies.

She nodded mutely as she breathed slowly and cautiously.

"But I remember her voice." He uttered hastily, shaking his head in disbelief, "It didn't sound like you."

"I had a cold." She told him, "That's why I was drunk as well. I'd had a shitty day at work, not eaten, taken loads of medicine and then hit the bar. Medicine, no food and alcohol is not a good combination."

He swallowed hard as his chest rose and fell heavily, not taking his eyes off her, "Wow." He chuckled nervously.

"Yeah." She agreed, a shy smirk beginning to take over her lips, "I don't usually do that kind of thing you know." She was quick to add.

His set of perfect white teeth began to show as he smiled widely at her, "I know." He assured with a nod, "I just wish I could remember more now."

"Oi." She scolded, unable to subdue a quite giggle.

"Although." He bargained, "There are certain parts I remember very very well." He said, his eyes wondering up and down the length of her body.

"Derek Morgan." She mumbled through gritted teeth, pushing him playfully on the chest, "You better get those images out of your head right now."

"No chance." He chuckled, with a quick suggestive raise of his brow and large grin.

She leant one elbow on the bar and let her head fall into the palm of her hand. "This is so embarrassing." She muttered.

He reached one hand over and gently gripped her forearm, pulling lightly so she revealed her face to him once again, "Hey. Don't be silly. It was a long time ago, and if it was embarrassing, it would equally be for me as it is for you."

"I guess." She agreed, unable to hold his stare, paying her attention to the nearly finished bourbon and desperately wanting the glass to be full again.

"I went back you know." He said.

She suddenly averted her gaze back to him, "What?"

"To Bennett's Bar. The next night. I know it was silly as I probably wouldn't have even recognised you, but I thought if you were there may be you'd remember me."

"Why did you go back?" She asked, her voice slight, but surprised and inquiring.

He shrugged, "I dunno. But something made me go back. I knew there was something about her….. Well, you I guess." He awkwardly smiled, a blush of embarrassment suddenly flashing across his face, "It was stupid really and of course you weren't there and then I left for Washington the next day so….."

"Oh." She said shyly, diverting her eyes from his once again.

There was a short silence in the air as both of their minds wandered back, and then he remembered, "Do you want it back?" He said.

"What?" She asked with a dipped brow.

"Your bra. Do you want it back?"

"Oh gees." She laughed with a shake of the head, feeling the awkwardness begin to dissipate, "Please don't tell me you've still got it."

"Maybe." He grinned, "Have you still got the matching panties?"

Her mouth fell open, feigning shock, "I think you remember a lot more than you're letting on buddy." She uttered, leaning into him so the bar man was out of earshot.

"It's all coming back to me now." He smiled.

"Stop it." She told him, slapping the top of his arm lightly.

"Anyway. What about you?" He asked, ignoring her vein attempt at scolding him. "What do you remember?"

She pursed her lips together as she attempted to stop herself from smiling, "Let's just say." She began, hopping off her stool and lifting the tumbler to her lips, "I remember a certain someone doing this thing with their tongue too."

She finished off her drink in one last mouthful, her eyes flashing at him over the rim of the glass, before placing it back down on the bar. She took a small step towards him and leant her body forward so her lips were by his ear, "….And their fingers." She whispered, him closing his eyes as he felt her warm familiar breath play on the surface of his skin.

When it disappeared, he quickly opened his eyes to see her turning on her heels and begin to walk away. "Right, I'm off to bed." She called back to him.

He stared wide eyed at her swaying hips and soft dark hair bobbing as she moved away from him, and then shook his head, snapping himself out of his Emily Prentiss trance. He gulped down what was left in his beer bottle and grabbed both of their jackets off the stool next to him, jogging to catch up with her.

"You left this." He smirked, handing the black fitted blazer that was balanced on his one finger.

"Oh thanks." She smiled, accepting it off him, "You off to bed too?"

"No." He shook his head surely, "I'm off for a very very cold shower…"

And she just stopped, shook her head with a warm, reminiscent smile and watched as he paced ahead of her, fumbling for the room key in his pocket.

So the post from the tumblr page was… During Emily's time working in the Chicago field office, she and Derek had a drunken one night stand, but they were both too wasted to remember each other.

Hope you enjoyed…. Let me know ;)