A/N: Special thanks on this chapter to CreativeReading, bkl125, and Moriarty-assbutt for being the loveliest people on the gosh darn planet.

The Interloper

by Flaignhan

She rolls over, burying her face in her pillow, trying to block out the sound of the crackling. She lets out a deep breath, and contemplates getting out of bed, but decides that that can wait - she's far too warm and comfortable at the moment, the duvet keeping her pleasantly toasty. She's not usually this warm in the mornings, and she can distinctly remember turning the heaters off last night. Loki wouldn't have turned them back on, he's in a constantly battle with her, adjusting the thermostat when she's not looking and twisting it right down to zero, or else throwing open the windows as wide as possible. And yet, she feels as though she's locked inside a solarium.

When she rolls over and opens her eyes, she sees red.

The entire room is engulfed in flames, climbing the walls, scorching the ceiling, the furniture ablaze. She gives Loki and almighty shove, inhaling sharp, shallow breaths, trying to gauge the smoke levels, but the air feels confusingly clean. Loki wakes with a start, and the flames vanish in an instant. His eyes are wide, panicked, his chest heaving, forehead glazed with a thin sheen of sweat. Natasha lets out a sigh, and presses her shaking hands to her face. It had felt so real this time. Before he had always simply set the TV or the bookcase on fire, and he had done it whilst awake. This had been the entire room, and he had been asleep. She had felt the heat of it on her skin, heard the crackle, had suffered that horrible, asphyxiating panic upon waking in hellfire.

"I'm sorry," he mumbles, throwing the covers off of himself and getting out of bed. He leaves the bedroom quickly, and moments later, Natasha hears the sound of the shower. She lays back down on the bed, her heart still racing, her skin tingling from the now subsiding adrenalin rush. She doesn't know what's gotten into him, but he is, apparently, just as unhappy about it as she is. He stays in the shower for a good half hour, and Natasha doesn't ask him any questions when she heads for the vacated bathroom. He's lying on the sofa watching Jerry Springer, a sign that things have reached a new low. She can hear the screeching and the bleeped out swear words while she gets dressed, but no sound of movement from him. In fact he doesn't move a muscle until she hands him a bowl of cornflakes, which he takes without a word, and quietly eats, staring into space as the commercials drone ceaselessly on.

"If you wanted something to do today," Natasha begins slowly as she fishes the last of her Froot Loops out of the pool of milk at the bottom of her bowl, her spoon clinking softly against the porcelain.

"Yes?" he replies, not bothering to look at her, his attention focused instead on the TV demonstration of a fountain pen that can stab through drinks cans.

"Well you could maybe cook something for dinner tonight," she says. "You could go to the store, buy some ingredients, follow a recipe…"

"You mean you wish to use me as a servant?"

Natasha rolls her eyes, then stands up, abandoning her cereal and the last of her coffee, and walks over to him, taking the TV remote from the coffee table and flicking through the channels.

"Some inspiration for you," she says, arriving on a cooking show, where a tousle haired chef is rapidly chopping up vegetables and tossing them into a pot. "I'll leave you some cash. If you don't want to it's fine, but if you do, option's there."

"Right," Loki says boredly, placing his half-eaten bowl of cornflakes on the table and laying back down, his thumb rubbing absentmindedly over the spot on his stomach where Natasha knows his scar is.

"Is it hurting again?" she asks, nodding towards it.

"It's fine," he says, his eyes following the movement of the knife across the screen.

"Are you fine?" she asks.

"Yes."

"What was the fire all about?"

He shrugs, and doesn't say a word, so Natasha sighs, giving up on any ridiculous notion she may have had about having an adult conversation with him. She pulls on her jacket impatiently, slings her bag over her shoulder, and leaves for work without saying goodbye. After their mutual bonding over trashy TV shows and emotional turmoil, she'd have expected him to be a little more forthcoming, especially when he's set her bedroom alight. Apparently, sleep arson achieves nothing more than building up the walls that had started to crumble, even if only a little.

She is used to the sound of explosions now, as is Thor apparently, because he doesn't even blink when a huge pulse of energy shudders through the lab, mugs of coffee tottering off of work benches and smashing to the floor. Natasha manages to clutch hers before it meets an untimely end, and Thor has to duck to catch his before it hits the floor. He smiles triumphantly when he only loses a little of his drink, and places his mug back on their table, while Natasha watches events through the glass screen of the lab. The smashed coffee mugs go ignored as Jane, Bruce and Tony gather around an object that Natasha can't quite see. Bruce has his arms folded, his index finger stroking his chin in puzzlement, while Tony's eyebrows are drawn together as he drops down to look at the object in closer detail. Jane scribbles away on her notepad, her pencil a blur as it moves speedily across the page.

"What are they even doing?" Natasha asks, craning her neck to try and get a half decent view of the object that is causing so much disruption. She has no such luck however, her view obstructed by Jane.

"Director Fury brought them a gift," Thor tells Natasha in a low voice. "The technology is not of Earth."

"Where's it from?"

"If I knew that d'you think I'd be letting Jane prod it until it explodes?"

Natasha smiles and looks down into her coffee. She doesn't know how to broach the subject without raising suspicion from Thor, but she wants, or perhaps needs to know more. She's not sure how much she can simply shrug off and explain away as curiosity, or whether it would be cruel of her to take advantage of Thor's grief, to press him for information that she knows he will only be too happy to give, so rare is the opportunity that he gets to talk about his brother to someone who doesn't consider that Loki's final moments were a well deserved result of karma.

"What was he like?" Natasha asks softly. "As a brother?"

Thor frowns and looks down at the table, the question catching him off guard.

"Sorry," she says quickly. "I…forget it. I was just curious."

"You're often curious about him," Thor tells her. "Did the run in on your ship really leave such a lasting impression?"

"Yeah," Natasha replies, resting her chin on the heel of her palm. "It did."

"Why?"

She shrugs. "He was different. The guys I normally deal with are usually motivated by money…"

"Vengeance was always Loki's greatest motivator. Vengeance against me, vengeance against my mother's killer…"

"Even when you were kids?"

Thor sighs, leaning back in his seat, and he runs a hand through his hair. He hesitates for a long while before he answers, and opens and closes his mouth several times until, at last, he finds some appropriate words.

"He wasn't always…" he trails off, his eyebrows drawing together in a frown as he reconsiders. "He was a good brother, a loyal son. My father and I didn't always understand him, he was different, but my mother understood him. She was always able to get through to him. But he took that for granted, I suppose. My father didn't give him the attention he craved, and so he was always trying to be recognised by him, but when he found out about his true parentage…"

"It destroyed him," Natasha says, and Thor nods, letting out a heavy sigh.

"It wasn't that long ago. Before that he was good. Far more level-headed than I was, and father would always pay more attention to his opinion on matters of the kingdom than he would mine. I was young, reckless, desperate to prove myself. Loki was even younger, but he was quiet, studious, understood the way things worked in Asgard better than I ever will."

"But surely if your father listened to Loki more than he listened to you - "

"Loki wasn't praised for his contributions. He was too young to be meddling in such things, but somehow, Father usually ended seeing that things happened the way Loki suggested. He was an excellent strategist, even when we were very small. He worked out how to get into the kitchens undetected and steal a handful of blossom buns while Sif, Fandral, and I waited outside."

"So you egged him on?" Natasha asks with a raised eyebrow. "You pushed him into a life of crime? Starting with blossom buns?"

Thor smiles sadly, his blue eyes blurred with nostalgia and grief. "We were awful to him sometimes," he tells her, his smile fading. "Because he was the youngest, and the smallest. We thought it was funny but…"

"But what?"

"We locked him in the cellar once," Thor says. "Just as a joke, we were going to let him out. We pretended it was a jail, and that he was a crook, so we locked him in there and we all sat against the door giggling while he beat his fists on the other side, demanding to be let out." Thor's frown deepens now, and Natasha stays silent, watching him intently, making a note of every single muscle that twitches on his face as he recalls the memory. His teeth pull at the inside of his lower lip, his fingers tapping on the table, almost anxiously. She's never seen him like this before, so riddled with guilt that he can barely find the words to explain, and a chilly feeling of dread starts to pool in her stomach.

"When he started crying, we tried to open the door, but the latch was rusty. It got stuck. He was so young, and he was so scared, and he didn't understand that we were only playing, he didn't understand that we were trying to open the door." Thor bites his lip and pauses, taking a deep breath before he continues. "Sif wanted to get my mother, but I didn't want to get in trouble, so I told her not to. But then Loki was screaming for us to let him out, because it was dark in there and he was always scared of the dark. In the end, Sif told me I was a fool, which, of course I was, and she ran to get my mother." He runs his hand through his hair again and lets out a sigh. "Fandral and I waited, still trying to open the door, but Loki had stopped hitting the door, and we couldn't hear him anymore. Mother arrived and prised the latch off with a dagger, pushed open the door and…"

"And?" Natasha breathes, hanging off of his every word.

"Fire," Thor says, closing his eyes. "Everything was on fire. The whole room. Everywhere. Mother ran down into the cellar, and I followed, and there he was in the middle of it all, hunched in a ball, sobbing himself raw."

"He set everything on fire?" Natasha asks, but she has a horrible feeling that she already knows where the fire stemmed from.

Thor shakes his head. "It was his magic. He was too young to control it properly, so when he was scared…fire. His hands were bloody from how hard he'd been hitting the door, and it took Mother almost an hour to calm him. I got the beating of my life for that one." He laughs hollowly, then drains the last of his coffee. "You only ever knew the worst of him, Natasha, he was my brother, until the very end. He was a good man."

"I know," Natasha says kindly. "If the world were split into good and evil then my job would be really simple. But it's not, and that's…well, it's shitty. It's difficult."

Thor nods in agreement, his hands clasped together, chin resting against them. Natasha decides she's gotten more than enough from him today, and turns the conversation away from Loki, not wanting Jane to return to find Thor miserable and emotional.

"So what are blossom buns?"

His morose expression vanishes at this, his eyes brightening, a smile working its way across his lips. "They're wonderful," he tells her. "We have them in the spring and they just taste…" He closes his eyes, apparently unable to put into words how delicious these buns are, but it's nice to see him smile, especially when she feels so responsible for his emotional downturn. Colour returns to his features, and it is as though the memory alone is bathing him in warm sunlight, washing away the pain and regret of some his childhood antics.

The object in the lab emits another, much stronger pulse this time, and Natasha and Thor both grab their coffees out of habit, sharing a smile as destructions sweeps its way through the lab, eliciting excitable reactions from Jane, Bruce, and Tony.

Fury's gift to the science team naturally comes at a price to Natasha's department. Or more specifically, to Natasha. Fury presents her with a set of leather gloves and tells her to watch out for the dogs this time. At the very least, she supposes, it is something to get her teeth into. She gets bored of hanging around HQ for too long, but heading back into that damn facility with those damn dogs when she achieved nothing of any importance on her last trip isn't top of her list for dealing with the boredom. She doesn't appear to have much choice in the matter however, because as soon as night falls, she finds herself creeping cautiously under a chicken wire fence and avoiding the spotlights that sweep over the grounds.

She gets inside through the same door as last time, managing to outwit the computer controls that are in charge of the locks with the same USB that Tony provided her last time. She supposes they don't need top of the range electronic security equipment when they've got dogs that can run like the wind and have teeth that could tear her to pieces in seconds. Nevertheless, she bypasses the firewall for the CCTV and sets it on a loop which they hopefully won't discover for a good ten minutes. Before she progresses any further into the building, she consults her map and works out the quickest route, then walks swiftly along the corridor, peering around the corner cautiously and continuing on when the coast is clear.

Her destination is in the basement, and she takes the stairs two at a time, putting all her weight on the balls of her feet, ensuring that she doesn't attract attention by creating a single decibel of unnecessary noise. The guy in the white coat doesn't notice her, far too absorbed in his notes as he paces around a large, gunmetal grey sphere that looks very much like the one in the photograph included in her briefing pack. She wants those notes in his hand, and, if possible, she also wants that grey sphere, but it's going to be a pain in the ass to get it out of here, especially if she's going to be chased by rabid dogs, and Fury's gift of the gloves suggest that she will be.

Just as she decides that knocking the lab technician unconscious is probably the best way to go - he's not armed, has average strength and won't be able to raise an alarm until he regains consciousness - the sphere lets out a few loud clicks. Natasha peers through the glass panel in the door, and the lab technician drops his notes, approaching the sphere. This is, apparently, a new development. Squinting, Natasha can see that several thin slots have opened up in the casing, and moments later, a sharp blast of red smoke is ejected from the sphere. The lab technician falls to the floor, and Natasha swears, throwing open the door to the lab, one hand covering her mouth, her nostrils squeezed tightly shut between her thumb and forefinger. She dashes inside, picks up the notes from the bench and tucks them under her arm, then grabs the technician by the wrist, dragging him across the floor and out of the lab, pulling the door shut behind her as the red smoke dissipates. She looks down at the notes, then at the technician and his pale face. Sighing, she crouches down, and feels for a pulse. It's faint, but it's there, and after a moment, knowing that she will be massively increasing her chances of being caught, she slams her hand against the panic button. Sirens start to wail and lights flash as she races up the stairs and down the corridors, throwing her weight at the door through which she entered the facility.

The notes flap noisily in the wind, and she clutches them to her chest, determined not to lose a single sheet and to get back to HQ before Jane, Bruce and Tony push their own piece of tech too far. She scales the fence quickly, the barbed wire catching on her gloves but not piercing them. She can hear the barking of the dogs in the distance, but by the time they reach the fence she is long gone, her legs carrying her swiftly over the uneven ground and back to the main road, where headlights flare as an engine roars into life.

"You didn't get it," Coulson says with a frown of disappointment.

"Put me through to Fury," she says, buckling her seatbelt with shaking hands as she tries to catch her breath, the thick folder of notes resting on her lap.

Coulson follows orders and within seconds, Fury's voice is on the other end of the line.

"Natasha?"

"It lets out a gas, get them out of the lab," she says breathlessly, resting her head back against the seat. "The lab tech collapsed. I dunno what's in it but it's dangerous."

"On it," Fury says. "Get back here and we'll debrief."

The line goes dead, and Coulson puts his foot down, streetlights blurring as they speed by. He makes it back to the city centre in record time, the silence hanging in the air between them, broken only by the rumble of the engine. The bright lights of the city blind her, and so Natasha turns her attention to the notes in her lap, thumbing through the pages to try and make sense of what's been recorded. It might as well be written in another language however, because she can't make head nor tail of the equations, nor the long strings of made-up sounding words. She lets out a sigh and closes her eyes, not opening them again until the car slows to a stop.

When they arrive in Fury's office, a sleepy Jane is already there, a bleary eyed Bruce sitting in the corner, his head resting in his hands.

"You okay?" Fury asks Natasha. "You didn't inhale any gas, did you?"

Natasha shakes her head. "Grabbed the notes, grabbed the tech, raised the alarm and left."

Fury nods, pacing around the room, his expression serious. "We're gonna need to lock it down, you guys can't work on it anymore. It's too dangerous,"

"You have gas masks, right?" Jane says, looking up at him. "If we take the necessary precautions then we don't need to worry, do we?"

"If it's an alien gas then our own technology may not be able to defend against it. Was the lab tech alive?" Bruce asks, looking to Natasha.

She nods. "Pulse was weak but yeah, he was alive."

Jane shrinks back into her chair, her face falling. She looks like Christmas has been cancelled, but if that thing goes off and they fall victim to the gas, she might not reach Christmas. Natasha passes her the notes, and she brightens a little at this, and soon she and Bruce are pouring over them, concentrated expressions leaving no room for smiles.

"I'm gonna head home," Natasha says, when it become apparent that she won't be able to contribute any more to the discussions. She's done her part, and right now, what she wants most in the world is her bed.

"No, you're gonna get checked over before you go anywhere," Fury says sternly.

"I'm fine," Natasha tells him, rolling her eyes. "Really, I'm just tired."

"Don't care," Fury says, fixing his eye on her. "You're going to get checked out."

"Come on," Coulson says quietly. "I'll get my two to make it quick."

Natasha sighs, knowing that there is no such thing as a quick post-assignment check up but follows him out of the office regardless, Fury's beady eye watching her closely as she departs.

"He's just worried about you. Doesn't want anything to happen to you," Coulson says as they wait for the elevator. "You're his best agent."

"Yeah I know," Natasha says with a sigh. "He'll have to get somebody else to do his dirty work if anything happens to me, and that'll take a lot of training."

Coulson frowns, and the elevator doors slide open. "What's that supposed to mean?" he asks as they step inside. He hits the button for the tenth floor and the doors slide shut obediently. Natasha shrugs, watching as the numbers above the door tick down, but doesn't reply to him.

"You chose this life," he says quietly. "You knew what it entailed."

I didn't choose this life," she snaps. "This life was chosen for me. I only got to pick the side, and I wasn't even granted that luxury until a few years ago."

Coulson doesn't say anything, and the elevator slows to a halt, the doors sliding open once more. Natasha strides ahead of him, not in the mood for a lecture on the necessary sacrifices of being a SHIELD agent, but Coulson catches up with her, taking her arm and holding her back from the med bay just before she goes inside.

"You're thinking of leaving, aren't you?"

Natasha shakes her head, but he raises a knowing eyebrow.

"I could have been anything," she tells him. "And it was decided for me that I would be this."

"I know," he says, releasing her arm and glancing down at the floor, his feet shuffling uncomfortably. "But you're the best in your field, and we value you here. We're not like those other places that just wanted to use you up until they got what they needed. We care about you."

Natasha skews her lips to one side, then pushes open the door to the med bay, tuning out her brain as an unnecessary amount of fuss is made. Blood samples are taken, reflexes checked, eyes blinded by pocket torches, and soon, the familiar swell of the blood pressure armband.

"Blood pressure is perfect," the girl says with a beaming smile. "Just want to do a quick a spirometry test and if that's fine then you'll be free to go!"

The guy wheels over a trolley and Natasha puffs several times into the mouthpiece presented to her, until the print out is satisfactory and she is permitted to go. She thanks the two of them, though Coulson repeats the sentiments a little more warmly, and follows her out of the med bay.

"I'll run you home," he says. "You must be beat."

"Thanks," she says, some of the tension leaving her. She shouldn't be angry with him, she knows that, she knows that he didn't mean to stoke the fire, but all the same, three words stick uncomfortably in her mind.

We value you.

He could have chosen any other words, but he chose those three, the three that make it sound like if the price is high enough, she'll be considered a fair swap. She is certain it was a simple slip of the tongue on his part, that he's not even vaguely aware of the impact of his words, that he will go to sleep peacefully tonight and will awake in the morning fresh faced and ready for a new day.

She, on the other hand, will toss and turn and wonder whether she ought to get out while she still can. There must come a point where she has surely given enough. There must.

They don't say anything on the car journey home, and Coulson bids her goodnight with a smile and a wave, and waits until she is safely inside the lobby before he pulls away. The concierge raises his eyebrow at her black kevlar suit and Natasha offers him a small smile, safe in the knowledge that he will not breathe a word of her late arrival nor her unusual attire to anybody. She's lived here for years, and he's worked here for even longer, no doubt thanks to the pride he takes in his unwavering discretion.

Loki's still awake when she gets home, laying on the sofa, his face lit with the unnatural blue hue of the TV screen. Natasha glances up at the clock and sees that it's gone three. He never stays up this late.

"Hey," she says softly.

He blinks and sits up, reaching across for the remote and muting the TV. When Natasha switches on the lights, he screws up his face in displeasure, shielding his eyes with his hands. Once his eyes have adjusted, he takes a good look at her, his eyes trailing slowly down her form, taking in every detail of her suit.

"Been busy?" he asks, quirking one eyebrow.

"A little," she replies, pulling off her gloves and tossing them onto the coffee table.

"I cooked."

Natasha glances up to the dining table, where one plate sits alone, knife and fork laid neatly either side of it, a glass of white wine, untouched, standing on a coaster.

"Poached chicken with glazed vegetables," he says. "It was on the TV."

"Looks good," Natasha replies, approaching the dining table slowly, guilt worming its way through her body with every step she takes. As soon as she knew she was going to be out for the evening, she should have gotten in touch with him. In truth, she hadn't expected him to cook at all, had thought that she would come home and find an empty pizza box with a few dollars change. She had never imagined that he would listen to her, and not only listen to her but make something that looks utterly delicious. She considers sitting down, taking a few token bites before she heads off to bed, but before she can pull the chair out, he speaks again.

"Don't bother," he says. "It'll be cold by now."

"I can heat it up."

"Haven't you already eaten?"

If by eaten, he means scoffing a deli sandwich during the assignment briefing, then yes, she has. She would have much preferred to have come home at the normal time to this, however.

"I can save it for tomorrow?" she suggests. "I'm sure it'll be - "

"It doesn't matter," Loki tells her through gritted teeth. "Just leave it."

"I'm sorry," she says with a sigh. "It was a last minute thing, I only got briefed at four o'clock."

Loki shrugs. "It doesn't matter," he says again, pushing himself up from the sofa and heading towards the bedroom. "I'm going to bed."

Natasha nods, and he disappears into the bedroom, closing the door behind him. She sinks down into the chair and starts picking at her chicken, still tender and juicy despite it being stone cold. She picks up her fork and then digs out a few glistening carrots, soft and sweet and oddly delicious even though they, like the chicken, have long since lost their heat. She takes a sip of her wine, and wishes that she'd made it home in time. How nice it would have been to return to her apartment after a long day, to a home cooked meal and a glass of wine. It sounds so normal, and she is envious of all those people across the city who made it home in time for dinner today.

The pleasant mundanity of it all leads her thoughts towards Sean, and she suddenly loses her appetite, places her fork down on her plate, and decides that it's high time she went to bed. She abandons her food, leaving the washing up until the morning, and slips quietly into the bedroom, the door clicking shut behind her. She unzips her suit, peeling it off and glancing over to Loki, who is breathing softly. Whether he's asleep or not is another matter entirely, but she's so tired she couldn't care less if he manages to get a squinty view of her silhouette in the dark. When she's yanked the suit over her ankles and is completely free of the damn thing, she pulls on her pyjamas and climbs into bed.

The duvet must be far too thick for the spring weather, because she can feel beads of sweat breaking out on her forehead, her neck dampening as well, and she kicks the covers off of herself, her heart pounding in her chest. There's no reason why her heart should be pounding, no reason at all.

But then she remembers the cheerful tones of one of Coulson's team.

Blood pressure is perfect.

She should have known then, but she had been so preoccupied with Coulson's choice of words that she hadn't let the girl's words sink in.

"Loki - " Her breath catches in her throat, her voice hoarse, and she tries to push herself up, but her arms are shaking too much to hold her weight. She perseveres, locking her shoulders and elbows into place as her entire body breaks into tremors, her lungs burning with every breath she takes.

"I told you," he says, rolling over to face her. "It doesn't matter."

"No Loki, I - "

Her elbows give way and she falls back onto the mattress with a thump, her muscles seizing up as she tries to force out words, any words.

The lamp flicks on, and the last thing she sees is Loki, peering down at her, before her eyes roll back into her head, and she is swamped in darkness.