A/N: I realize I'm a bit late for a Halloween fic… but this was actually inspired by the last episode and Nick's new look. I figured I'd try to explain where it came from. I noticed Forensicsfan beat me to it, but since it's almost completely written I'll post anyway. It is several chapters. I'm only putting the first right now so I have more time to finish it off. Hope you like it. Let me know either way.

"Hey you," Nick Stokes greeted his guest with a welcoming smile, most of which was covered by large dark moustache that had taken over the space between the tip of his nose and his upper lip.

"Hey," Sara replied with a similar smile, except hers was completely visible. She tilted her head as she noticed he was sporting a different look from the last time she saw him. "You missed a spot shaving," she said as she removed her jacket.

Nick was going to reply but got distracted when he saw what she was wearing, "A scientist? Really?" Sara nodded self-consciously as she glanced down at her costume. She was wearing a large white lab coat, borrowed from work earlier that day, with odds and ends hanging out of the pockets. Among the clutter were pens, pencils, a magnifying glass, a calculator, tweezers, and an empty beaker. Basically Sara had been strapped for time and, having never gotten around to finding a costume, she improvised by visiting the lab and grabbing anything that would make her costume obvious. She had even gone to the effort of topping off the look with thick-framed glasses and her hair pulled back into a chaotic pony-tail. "Way to think outside the box, Sidle," Nick said.

He was a little disappointed in her costume choice; he had tried not to get his hopes up, realizing that he knew Sara well enough to assume it wouldn't be the case, but its just that every other girl in the world seemed to use Halloween as the perfect excuse to dress as scantily as possible. Really, only half of him was disappointed… the other half was proud she hadn't put on lingerie and a fuzzy set of animal ears pasted to a headband and tried to pass it off as a "bunny" or "kitty" or "insert-your-cutesy-animal-of-choice-here". So, with that in mind, he surveyed her costume once more. The muscles in his face slowly tugging his lips into a smile; how she had managed to make a seemingly geeky scientist sexier than a "bunny" he'll never know.

"You forgot about tonight, didn't you?" he accused, doing a fairly good job at hiding the hurt that otherwise would have been accompanied this thought. "You remembered last minute that we had made these plans and searched your closet," he said the last part with tiny smirk, hoping that the lab coat actually was hers.

"No, I remembered our plans. I was actually really excited about this," she noticed Nick's grin get impossibly wider. She realized that he could read too much into that statement – read into it correctly, but that's not the point – so she hurried forward to cover. "Uh, you know… I haven't handed out candy since I came to Vegas, so I'm excited to see all the kids having fun." Nick just looked at her, still smiling broadly. "'Cause I don't get any kids at my complex on Halloween," she continued, wishing he would stop look at her like that: that cocky smile rubbing her nose in the fact that she had really been looking forward to tonight for the previously assumed reason. "I mean who goes Trick-or-Treating in an apartment?" When the look still hadn't disappeared from his face Sara entered the rest of the house, socking him in the arm as she passed him a few feet in. "Shut up… and I'll have you know that I stopped by the lab today, on one of our rare days off, just so I would have a costume."

He followed her into his living room, where he noticed she immediately made herself at home by plopping down onto the couch and propping her feet up on the coffee table. Nick walked into her field of view, rubbing his bicep with a pronounced pout despite the fact that she had only punched him lightly. "There are rules for dressing up, you know; one of them being that you can't 'dress up' as what you are everyday," he spoke pointedly, collapsing a couple inches away from her on the couch.

"We're not scientists. We're forensic specialists. Jeez Nick, I figured you'd know your job description by now…" she gave her most charming grin.

"When I explain my job to my nieces and nephews, I tell them I'm a mix of a cop and a scientist. And you just said that you got your 'costume' from the lab, therefore it is exactly what we wear everyday," he loved the annoying her.

She gave up, "Look, it was either this or nothing."

'Nothing, eh? That's even better than bunny,' he felt a goofy grin take over his face as his mind raced with the idea she presented. After a beat he realized he hadn't retorted yet, "See now that's not a look you have everyday. I vote you wear nothing." He completed the cheesy statement by waggling his eyebrows suggestively.

She blushed. "Well, since I obviously voted in favour of the scientist I guess we're at a stalemate," she shrugged with a "what-can-ya-do" expression.

"Hmm…" Nick considered the problem for a minute, "Okay, the only way to resolve this is to compromise: take off your shirt."

"Nick!" Sara swatted him in the arm, not quite sure how else to respond to that.

"You're right. Then you'd lose the lab coat and that's really the bulk of the 'costume'," he air quoted costume. "I guess you'll have to lose the bottom half then," now he wore a hopeful expression. Both faces suddenly felt very warm.

"Why don't you go finish your costume and let me worry about mine?" she suggested, willing her cheeks to return to their normal colour.