"Hey, Barton!" They turn at the shout, find one of the agents from Alpha Team striding down the corridor behind them. "Fury's looking for you. Gym on the fourth floor."

Natasha has a little stab of disappointment at the interruption, a silly, childish thing to feel. Pizza can be reheated, or eaten cold. Clint isn't picky, he won't mind.

"Romanoff, too," the agent adds without meeting her eyes. None of them really look at her when they talk. Clint frowns, as he always does when his colleagues pretend she isn't standing right beside him.

"He say what it's about?"

The agent shrugs, mutters "Sorry, man," and continues down the corridor.

"Let's go get yelled at," Clint says, too brightly in her opinion. He takes her hand and drags her along after him.

"We haven't done anything," she protests. The words lilt into a question, because Fury chooses strange things to ride them about. "I kept the body count at five in Switzerland."

"Maybe it's a speech about how we should try to exceed our goals, 'stead of just being satisfied with meeting them on a technicality."

Clint smirks, and she sticks her tongue out.

"Number six still had a pulse when we left," she reminds him, and he barks a laugh.

The gym on the fourth floor is massive, and Natasha's never liked it, too many whispers and too much staring. She prefers the tiny gym on level seven, or the shooting range, or that room on the R&D floor where she and Clint are allowed to blow things up and call it weapons testing.

Something feels off as they advance down the hallway, some unnameable instinct slowing her steps enough that Clint glances back to find her as he pulls open the gym door.

It's dark inside, for a moment, then the lights go up and a collective shout of "Surprise!" echoes down the corridor.

Natasha's pulse jumps in that uncomfortable anxious way, when she would ordinarily strike first and ask questions later but can't because she's with S.H.I.E.L.D now. Clint just says "Awesome!" and pushes his way into the gym without her. Curious now, she follows.

The exercise equipment has all been moved out. Someone's strung hundreds of lights around the walls, strobe lights and mirror balls and the twinkly white ones from the company Christmas party Clint dragged her to six months ago. There's a DJ booth and a long table of catered food and a cake and beer kegs and...oh.

Her stomach drops, this time not out of nerves. The sensation pairs with a heavy weight of disappointment and a twinge of embarrassment and that stinging feeling in her throat that means she's about to cry.

It's not the fact that the party was clearly put together in secret, or that she was only invited because she happened to be standing right beside Clint at the moment. She doesn't give a single shit about any of the three hundred assorted S.H.I.E.L.D agents gathered in the gym, and nothing they could conceivably do would ever hurt her feelings.

No, it's the pizza and cupcakes she hid in Clint's quarters half an hour ago, the gift wrapped in shiny purple paper sitting on his coffee table.

Clint likes people and belonging and talking and laughing and of course he would rather be at this kind of party, instead of cooped up in his quarters all night, and she hadn't even thought of that because she doesn't have a frame of reference for birthdays because she's Red Room, the Black Widow, Barton's stray, the girl people skirt around in corridors and she'll never get it right-

"You're good," Clint says appreciatively, coming over to nudge her shoulder. "Like, I know your job is to keep secrets and shit, but...you're good."

It would ruin the mood to admit that she had no idea the party existed until two minutes ago; Clint thinks she was involved, and he always gets pissy when the other agents exclude her from things, although she hasn't been able to work out why it matters so much to him.

"Go enjoy your party," she says, playing smug. He buys it, too distracted to notice her smile is a little too forced. He wrangles three sniper buddies and they disappear across the room, in the direction of the catering spread.

And this - this feeling of absolute mortification - is what happens when sentimentality gets in the way of logic. Lesson learned. Now she has to fix it.

It won't be much different from any other mission. She's done it a thousand times: infiltrate a party, snatch a key off the unsuspecting host, disappear upstairs to retrieve the money or the launch codes or whatever insignificant objective the man keeps locked in a safe. She's already stolen Clint's identification badge once today to gain access to his quarters and set up her own surprise. It shouldn't be difficult to do again.

She makes a circuit of the gym, keeps her ears open. It was Clint's Special Ops friends who set up the party, she learns, the snipers and combat tacticians he hangs around with most, when he's not with her. Of course they know what he likes.

She's good at belonging without actually belonging. She chats with Maria and Sharon and Coulson and makes sure Clint sees her interacting; if he gets hyper-vigilant worrying about her having fun, she'll never sneak his identification. She lets him goad her into doing a keg stand. She cheers when he wipes the floor with his friends in a dart throwing competition, and here it is, the opportunity she's been looking for.

"That's not even a challenge," she scoffs to the woman standing beside her, a girl from accounting she knows has her eye on Clint. "Barton could beat them all blindfolded."

And, as expected:

"Blindfold!" the brunette shouts, bouncing on her toes and thrusting her hands in the air. Other agents echo the idea (S.H.I.E.L.D agents are easily amused, she's discovered, no better than cats with a laser pointer) until a bandanna gets thrust into Clint's hands.

"Good luck," she tells him, stepping forward to tie the bandanna around his eyes.

"It's called skill, Red," he quips back.

An agent slaps three darts into his open palm, another one takes him by the shoulders and forces him to make three quick turns on the spot. Natasha nudges past him and quickly unclips the badge from the belt loop of his jeans.

She doesn't leave, not immediately. She takes her place in the half-circle of agents gathered to watch the dart game, cheers loudly enough for Clint to distinguish her voice from the others as he lands the first bullseye.

Everyone's distracted after that and nobody notices when she sneaks into the corridor and up the stairwell.

That feeling comes back, shame burning hot in her chest. It makes her heart slam frantic against her ribs, a sense of urgency she's never felt on a mission before, a voice hissing in her ear to cover her tracks before she's found out and has to face Clint with an explanation. The thought makes her stomach twist.

The hallway she ducks down on the residential floor is empty, and at least something's going right tonight. She stands in front of his door, swipes his badge. The lock clicks.

She doesn't have a plan, besides stashing everything in her own room and dealing with it later.

"Natasha."

Shit.

She turns and smoothly conceals his badge in her pocket, opens her mouth but can't find any words. The door handle grows slick beneath her palm as Clint strides down the hallway.

"What are you doing, Natasha?"

The words are weighted, suspicious. She shakes her head, shrugs a little, can't find an excuse. She certainly doesn't want to tell him the truth.

"Let's go back to the party," she tries. Clint scowls.

"You're good," he says again, but this time it isn't a compliment. "Nine months is a long time to keep a cover going." He strides forward and she pulls his door quickly closed, presses her back against the cool steel. "What are you doing in my room?"

"Nothing," she says, and sure, that sounds completely believable.

"Move, Natasha," he says, firmly but quietly, and the disappointment tempering the words is worse than any shouting. She doesn't move, so he moves her himself, a soft push to the side. He takes his badge from her pocket and swipes it through the reader beside the door.

She knows what he's thinking and she can't fault him for it. She took credit for the party, spent the entire evening trying to distract him. He's clever and observant, he can probably recognize by now what it looks like when she works a mark. Hell, she'd rather him think she turned on him than see the sad little display in his apartment.

It's the perfect opportunity to run, while he advances cautiously into his quarters, but there isn't much point. She'll have to face him eventually. Her room is three doors further down the hallway, obvious, a terrible place to hide.

She leans against the wall instead and waits for him to laugh, or say something in that overly-polite tone he uses when expressing gratitude he doesn't actually feel.

"Asshole, Barton," he mutters, then louder, "Nat? I'm sorry, I-"

He steps back into the corridor and draws up short when he finds her where he left her. She can't quite meet his eyes.

"You weren't supposed to see."

"I'll leave if you're not done," Clint offers. He gives her a grin. "Swear I'll still act surprised."

She could still salvage the situation, pretend the mess in his quarters was meant to be the second part of the birthday celebration. It seems like too much effort. She's tired of pretending for the night.

That vulnerable feeling is back, a fluttery nervous sensation in her chest. She's tired of that, too.

"I was going to clean it up. It's stupid."

She stares him down, shifting into defensive mode, daring him to lie and insist otherwise. Arguments are easy, safe. Better than whatever spurred her into the gross display of sentimentality in Clint's quarters.

"It isn't stupid, Tasha."

He ignores her glare and pulls her in for a hug; she keeps up the pretense of fighting for another moment, shoulders stiff and palms pressed flat against his chest in protest, but it doesn't last. She leans into him, and he sighs against her hair, and the sick feeling in her stomach disappears.

"The other guys just wanted an excuse to order kegs and spend S.H.I.E.L.D's budget. I like your party better."

"It's ruined by now-"

"Stop whining, it isn't ruined. So we have to nuke the pizza and put the beer in the fridge, big deal."

He pulls her into his quarters with an arm around her shoulders and shuts the door. The champagne bucket full of beers on the kitchen table is dripping water on the floor, but the pizza and cupcakes are intact, and the balloons haven't gone flat. It's not as much of a disaster as she imagined.

Clint snatches his gift from the coffee table and shakes it on the way to the kitchen, then opens the envelope taped to the wrapping paper. He lights up at the fluffy golden dog on the front of the card, flips it open and mutters "Happy barkday" to himself.

She watches closely, because she knows she got this part wrong; she couldn't think of anything to write on the inside, and instead just signed her name.

"Nice," he says with a grin, and sticks the card to the fridge with a magnet. He slides the gift in carefully beside the cupcakes and little pack of candles. "We're supposed to wait until after pizza, but-"

"It's your birthday," she tells him. He gives her another big smile and shoves half a cupcake in his mouth.

"See, your party's better because you made my favorite. I didn't even know German chocolate cupcakes were a thing. The other guys just ordered that huge boring birthday cake."

Maybe he's trying a little too hard to make her feel better, but it's working, and she doesn't call him out.

Clint cleans up the melted ice and champagne bucket while she puts the pizza on paper plates for the microwave. It doesn't really feel special - besides the cupcakes and the gift, it isn't any different from how they usually spend a Friday night - but there's something easy and comforting in the way they maneuver around each other, and how she knows to put three slices of pizza on Clint's plate without asking. She knows where they'll sit on the couch and she knows which movie he'll choose. The effortless familiarity is what she'll pick, if Clint asks what she'd like to do for her own birthday.

"Watch this," he says, and lays his phone on the table. He pulls one of the balloons tied to his kitchen chairs, unties the knot at the bottom while his phone puts a call through.

"This is Fury," comes from the speaker. Clint sucks a deep breath of helium from the balloon.

"Heeeeey Nick!"

He catches her eye and snorts a laugh. She can't help but smile back at how ridiculous he sounds.

"Agent Barton," Fury replies, perfectly composed as always, but there's a hint of amusement hidden in the words.

"Nat wants to tell you something," Clint says in a rush, and thrusts the balloon at her.

She hesitates, but only because something between them feels different. A good different, a brighter spark of energy, something more than the usual quiet comfort of Clint's company. It's struck her once or twice before, small moments too happy to be real, unsettling enough to make her push him away.

Clint waits with a big grin, an expression so genuinely enthusiastic she can't turn him down. She doesn't want to, not this time. She finds herself smiling back.

Fury grinds out a sigh, but obligingly waits for whatever nonsense she's going to come out with. She takes the balloon and sucks out the helium, and now she believes Clint. Her party is way better.