The rec hall is teaming with people.
Lestrade must have invited everyone from the precinct, each department clumped together in tight-knit throngs; the officers at the heart of the room partaking in a rowdy drinking game, then the more socially awkward, slightly uncomfortable-looking lab techs milling about the edges.
It's the fraying fringes of the crowd that Sherlock instinctively combs for Y/N---his eyes taking through the tangle of bad Christmas jumpers and Santa hats.
A man dressed as Buddy the elf steps aside to fetch some punch from the buffet table, and Sherlock's steps falter.
There she is.
She's wearing a holly-berry red strapless dress, the disco lights spinning a colourful dance on her bare shoulders.
It's strange seeing her without her lab coat.
Nice strange.
Very nice.
She's chatting to a small group of people Sherlock recognises from her department (although it takes him a moment to recognise them without computer monitors hiding half their faces).
Sighing, he approaches them, knowing that---even if Y/N were not here---this rag-tag group of outcasts is where he belongs.
He has met two of them before, and the other is new to him, but the rectangular pages of a well-thumbed pocket novel poke out of her bobbly snowman cardigan, which works instantly in her favour.
Sherlock doesn't trust people whose books are pristine. Unbroken spines means they're untouched, and therefore unread, and therefore only for decorative, vein purposes. A tidy bookshelf says 'I am so clever, look upon my collection'.
Like his brother's.
Sherlock had known he liked Y/N as soon as he saw her because she had been reading the most dog-eared book he had ever set eyes on.
She'd been shovelling a hasty lunch from a Tupperware tub into her mouth, a battered novel spread on the lab bench with her free hand. The pages were yellowing and the edges soft, and she'd been so absorbed in the smudged, inky letters she hadn't heard Sherlock come in.
When he'd greeted her, her cheeks had glowed with two red circles, and he'd been so taken by it he'd forgotten why he was borrowing the lab in the first place.
Y/N blushes as he greets her now, and his cheekbones heat.
He wonders if she can tell he spent half an hour getting ready earlier. He wouldn't usually. He wouldn't, ever. He'd wear pyjamas to CoOp if it were socially acceptable.
Today, however, he'd taken his time choosing his best shirt, tucking it in neatly--even fluffing up his hair in the bathroom mirror.
For reasons he doesn't quite want to explore yet, he'd like Y/N to think he looks nice.
She looks nice.
(Trying to keep his eyes from lingering on the smooth line of her collarbones) he tells her, and she turns a deeper shade of pink, the colour dribbling all the way down into the front of her dress.
He'd like to tell her other things---that he likes what she's done with her hair, and he hopes she's having a good time---
But the man to his left pipes up:
"I'm surprised to see you here." The man's name is Elliot, Sherlock remembers vaguely (or maybe Evan) and if anything, Sherlock is more surprised to see him here. He's several inches taller than Sherlock, but the same width, making him look as if he'd been squeezed through a Playdough playset.
Sherlock can't remember anything else about him besides the fact that he likes trains, and he only really knows that because his tie has a train on it.
"And why is that?" Sherlock snaps back, and then regrets it. He's sick of people making assumptions about him, even when they're right.
What is he doing here?
"I'm surprised you're all here," Lestrade says, and Sherlock feels an arm fall onto his shoulders. It pulls him into a stoop and he has to ease out of it before they both topple over. Lestrade smells of eggnog and Doritos, but he's smiling widely below a fake Santa beard, and Sherlock can't help his lip twitch.
...
The rec hall's blinds are drawn on the outside world---so the street lamps won't interfere with the disco lights---but Sherlock can tell by his watch that the moon is high in the sky.
He's remained with the little group of rag-tag nerd-type peoples, and even eventually felt quite at home.
Several of the males remind him of his brother; blunt and slightly arrogant, and he's been enjoying listening to the older woman with the pocket novel---Gloria---tell him about her three mastiffs. She's promised to meet Sherlock in the park sometime so he can say hello to them.
Sherlock is halfway through telling Gloria about his childhood dog when a snippet of Ryan---a short young man from the IT department's conversation catches his interest.
"Okay okay okay..." Ryan says, trying to stifle his giggles. He's holding a plastic cup full of fruit punch in one hand and seems to have refilled it several times. "...The public library."
"Really?" Gloria asks, Sherlock's dog anecdotes forgotten.
"Yeah," Ryan continues, nodding. "In the parenting section. Ironic huh?"
Sherlock laughs with the group although he doesn't really know why.
"Did anyone see you?" Someone asks---they'd meandered over, overhearing the discussion on the way back from the loo.
Ryan shakes his head. "Nah, library was closed. She worked there and we'd locked it all up."
Train guy (who Sherlock now knows is called Ethan) waves his hand like he's swatting away an annoying fly. "It's not a crazy place if it was closed. Where's the danger?"
"Well, it was better than yours," the new guy defends Ryan, who looks surprised.
They probably haven't spoken before now, and probably never will again.
"Where's the danger in hooking up with someone at a comic convention?"
Ethan's lips purse. "He was in costume! He could have been hideous under the mask, or--or a serial killer. You don't know."
"If he was a serial killer at least you'd've had your lightsaber to defend yourself," Gloria quips, and everyone sputters.
Almost everyone.
Sherlock catches Y/N in the corner of his eye.
She must have slipped away at some point because she's now at the buffet table, pouring herself some punch. She takes a long drink from her plastic cup and---to Sherlock's surprise---refills it.
When she comes back over to the group, her feet are unsteady.
Sherlock guesses that isn't the first cup she's had this evening.
He would find her stumbling about amusing if she didn't look so wilted.
Now that he thinks about it, she'd fallen quiet some minutes ago---so quiet he obviously hadn't noticed her slink over to drain the punch bowl by a few centimetres.
Excusing himself, Sherlock places a steadying hand between Y/N's shoulders.
She lets him, stumbling along next to him pliantly as, trying to ignore the warmth of her skin against his palm, Sherlock steers her to an empty spot by the wall.
"How many of those have you had?" He asks wearily, gesturing to the cup in her hand.
The punch is supposed to look red---for Christmas---Sherlock thinks, but it's had so much spirit added it's almost pink, and Y/N has already drained most of it. Lestrade had made it himself; he'd told everyone proudly. He'd also warned---jokingly---that it can't legally be called Punch.
Y/N shrugs. "Three? They're good," she says unconvincingly. "Have you tried one?"
"I prefer to avoid alcohol," Sherlock says flatly. He hopes she assumes his sobriety is to keep his deduction skills whetted like a blade, and not the actual reason; he actually just prefers a good cup of tea. "Especially this alcohol because it's so potent I'm surprised it's being served by officers of the law."
Y/N's brows come together. She didn't seem to catch many of the words, but one definitely did manage to sink in. "There's alcohol in this?"
It almost makes Sherlock chuckle. "Yeah. Couldn't you tell?"
She thinks for a second. "Now that you mention it...the floor is going...sort of to the left."
Sherlock is surprised at her apathy. He doesn't know if Y/N usually drinks, but if he were to bet money on it, he'd say she probably doesn't. He'd expect more of a reaction from someone who's just been told they've gotten quite accidentally drunk.
Softly, Sherlock takes her upper arms and props her upright.
She gazes up at him, if he didn't know any better, he'd say sadly.
"Y/N," he prompts gently. "Are you all right?"
Y/N waves him off, almost like a moody child. "I'm a grown woman, Sherlock, I can have a drink if I want to."
Sherlock blinks.
She'd been smiling earlier. Happy. At ease with her friends, relaxing after a long week of work.
Sherlock had been glad she was enjoying herself. He gets the feeling, when he's around Y/N, that she doesn't enjoy herself as much as she should. She just doesn't seem to be very good at it. Even when she's relaxing, she'll be bouncing one leg, nibbling the white from her nails, glancing around; as if she expects something to jump out from behind the furniture and pounce on her.
She'd visibly unwound a little this evening, though, Sherlock had been delighted to find.
Then, at some point, she seems to have clamped up again.
Sherlock shakes his head. "Of course, you can drink what you like," he affirms. "What I meant was, you seem sad."
"'m not sad," Y/N says, shaking her head. The movement seems to make her vision reel because she stops, swaying a little on the spot.
Sherlock offers her his arm and she holds it, steadying herself. Making a decision, he starts directing her to the door.
Y/N watches the crowd go past like she's absently gazing out the window of a train.
He carries on, out of the hall, out of the building, and Y/N frowns up at the night sky as if she hadn't expected it to be there. A little slurred:
"Where are we going?"
Sherlock's breath clouds in the brisk December air as they make their way to the main road, releasing Y/N for long enough to shed his jacket. Gently, he threads it onto her shoulders, helping direct each hand into the sleeves.
They're too long for her, and she hugs the material about herself like a blanket.
It makes Sherlock smile. "I'm escorting you home."
Y/N doesn't say anything, perhaps because she thinks that's a good idea, or perhaps because she's just too drunk to form a reply.