A/N: If you follow me on tumblr, you've likely seen this first chapter that was a response to the prompt "alien invasion au", which I couldn't resist continuing. Hope you enjoy this apocalyptic little journey with me.
It's through the scope of her rifle that she notices the man on the street, a younger girl with bright red hair - hair that shone far too brilliantly, too noticeably, in the morning light - clinging to his hand, sticking low to the concrete, pressed against an abandoned car.
After New York had been decimated by the tsunami two months ago, not many had survived, a city of 8.4 million practically washed clean of human life, and the streets were littered with waterlogged debris, the bones of fish, of… people. But most had been swept away, a death at sea, and sometimes, Kate wishes she had been one of those 8.4 million.
Instead, she had somehow managed to survive the massive wave, held on and held her breath long enough to survive the crash, the explosion of water and glass as the windows had burst open under the pressure. She hadn't been the only one, but the natural disaster had only been a prelude to the true climax of terror.
Surviving a tsunami? Difficult, but doable. Surviving intelligent lifeforms with high powered weapons that obliterated human flesh with a single zap? Not so much.
The monsters that had invaded Earth had taken out each survivor one by one, but Kate Beckett refused to fall victim to this human extinction event, not at the hands of them.
Aliens, she had learned, were far from the little green men she had always pictured, nothing close to what she had seen in her viewings of the X-Files as a teen. She had never seen their true form, hoped she never had to, but since taking over the planet, she's witnessed them adapt. Stealing the faces, the not too badly damaged bodies, of the dead. Resurrecting them, using the shells of people to masquerade around in, and Kate would put a bullet in her own skull before she allowed herself to become one of them.
The newcomers to the planet were practically genius, smart enough to know how to trick humans, and it's the reason her finger trembles over the trigger now, her aim on the girl's head first. There was no way to know if the two were humans, survivors like her, or just a pair of monsters wearing a dead father and daughter's faces.
Before Kate can decide, the choice is taken from her.
The girl screams and Kate curses, redirects her aim from the top window of her apartment building to the soldier wearing sunglasses, following after the two, his movements smooth, but mechanical. The man with the girl jerks her behind him, draws his gun, but the faux-human raises his handgun first.
Kate fires.
A silent bullet tears through the air, sears through the alien's temple, a flash of light rippling through its eyes, bright enough to glow behind the shield of glasses, before it crumples to the sidewalk.
They always wear glasses, he's noticed, to hide the inhuman glint of light circling their pupils. He never imagined sunglasses would scare him shitless, but the sight of them never failed to send his heart skipping in horror these days.
Rick immediately swings his gaze upwards, follows the line of the shot to an apartment building, a boarded window with the head of a rifle peeking free. He doesn't know his savior, but he wants to, and he tugs Alexis towards the building, intent on his daughter's safety.
"Dad, wait," Alexis hisses from behind him, jogging to keep up. "How do we know-"
"We don't know anything," he replies, crossing the street, weaving through clusters of abandoned cars. "But they saved us and that has to count for something."
"What if they're bad?"
"They can't be worse than those things," Rick mutters, flicking his gaze back to the dead one on the sidewalk. "I'll take horrible human over alien any day."
The entrance to the apartment building is chained, locked, and despite all his rattling, he can't break past the barrier.
"Stop making a racket."
Rick stiffens, tugging Alexis into his side and reaching for his gun, but the voice that had made the instruction already has hers raised, trained on his forehead as she comes around the side of the building. Her eyes are critical, roaming between him and Alexis, assessing with caution and a shimmer of fear every human being now wears like the latest trend.
But no glimmer of an alien glow in her irises.
"What are you doing in the city?" the woman demands, her voice low, lethal, and exhausted. "People avoid it like the plague."
"We survived the tsunami, as it looks you did as well," he murmurs, shifting from foot to foot. It sends a wave of unease through his stomach to be out in the open like this, not moving, and he can sense that the woman isn't enjoying it much either, her eyes darting up and down the street every other second. "We'd been holed up in our home since this all began, but our loft was devastated and we've been running low on supplies, so my daughter and I have been trying to find a new place to… to ride this out."
The woman's brow arches and Rick immediately narrows his gaze, flicks it to Alexis and back, and she thankfully seems to understand.
My daughter still has hope that there will be a happy ending to all of this. Please don't crush it.
The woman bites her lip before she slowly lowers her weapon, gestures for them to follow.
"Haven't you learned that dusk is the best time to travel?" she mumbles, keeping her eyes over her shoulder as she leads them to a back entrance, allowing them both inside before dead bolting the security door behind her.
She startles harshly when Alexis powers on her flashlight, an embarrassed flush filling his daughter's cheeks when the woman glares back at her for it, but she softens after a moment, offers his daughter a sad attempt at a grin when Alexis extends the flashlight towards her.
Tough exterior, but still soft enough to show his daughter kindness. Not to mention saving his ass from being vaporized. He's already beginning to like this woman.
"What's your name?" he asks once she deems the locks secure and starts towards a dim stairwell, Alexis's flashlight casting shadows across the steps.
"Does it matter?"
"Does to me," he quips. "I'm Rick and this is Alexis, and I'd like to formally thank you for saving our lives."
They reach the top of the stairs and the woman sighs. "It's Kate."
"Kate," he murmurs, her name rich on his tongue, appealing. "Thank you."
"Don't mention it," Kate mumbles, continuing down a short hallway and producing another set of keys from her belt, unlocking the third door on their left. "I've been here since the invasion. Most of the tenants to this place evacuated, others were… well, the tsunami, and now it's just me."
"And us," Alexis chimes in, her smile tentative, but hopeful. His daughter was still so hopeful and it terrifies him.
Kate hesitates, but nods, lets them inside her apartment and locks the door behind them with tense shoulders.
"How have you managed to avoid being found?" Rick inquires, observing the space of what once was her home. The walls ruined, wallpaper peeling and frames of art blotched with water stains, the furniture not faring much better, but it's nicer than any place he's seen in months, and most importantly, it's safe.
"I've been watching them. They sweep through the city, catch anyone on the streets, the cars, anyone in sight, but I think their time is otherwise occupied. What's left of the human race is a small number and they obviously know they can outsmart us, so they're in no rush," Kate explains solemnly, drifting into the kitchen space and snagging an opened pack of crackers from the island. "Here, you look starved."
"So do you," he argues when she tosses him the food, but Kate ignores him. He hands the crackers over to Alexis. "We'll contribute, help you gather supplies, anything you want, if you let us stick with you."
"Strength isn't in numbers anymore, Rick," she murmurs, her eyes downcast, her cheeks hollow, the lines of her face carved out with loss and trauma.
"I disagree. You should have someone watching your back and we need someone watching ours," he continues, watching her lips purse, but he's getting through to her, burrowing past the stone cold exterior and the tired eyes. She's been alone for a while, probably as long as they have, and surviving alone may be easier, but it isn't better. The strain of it sucks the life from your bones, the humanity from your brain; it turned you into a lifeless machine intent only on making it through each day, each night, and it wasn't enough for him, for his daughter. And he refuses to believe it's enough for Kate. "Someone who knows better than to wander the streets in the middle of the morning."
Kate's gaze flickers up to him, something akin to amusement flickering to life in her irises, and she sighs, a sound of relent.
"Fine." Rick beams and extends his hand to her, quirking his brow when she regards his proffered palm with disinterest, before huffing and striding forward. Kate curls her fingers around his, her digits cool and slim, and gives his hand a firm shake, chuckling when Alexis drops hers over their clasped palms. "We'll try it out. Just for now."
Now is all he needed. Now is all they had.
Alexis is a quick study, taking instruction from Kate with ease while she trains her with the rifle the next morning. They don't fire any shots, the risk of noise too dangerous, ammunition too precious, but his daughter is young enough to adapt to this new world, to learn to kill without flinching, to survive without it costing her soul.
Rick, she notices, has a harder time. He's rooted in the past, in the hope that it's not all lost, that it can't be. Just like she is.
"Who were you, before this?" he asks her on the third day of this… partnership. Her instinct is to tell Rick it's none of his concern, that it doesn't even matter now, but his blue eyes are filled with so much yearning for something she doesn't understand. Something that doesn't have to do with the invasion, the apocalypse, the end of their world.
"NYPD, homicide detective," she answers, resisting the urge to fiddle with her mother's ring beneath her shirt. "You?"
Rick takes a second to answer, his eyes still lit up with what looks like astonishment from her response, and he has to blink a couple of times before his previous profession tumbles from his mouth.
"Mystery writer."
"Anything I'd ever heard of?"
He nods towards her battered bookshelves, all of the ruined novels still in neat rows. "Richard Castle."
Kate cuts her eyes back to him, scrutinizing the exhausted face of the man staring back at her. He's almost unrecognizable.
"Big fan, Kate?"
She swallows but manages a shrug as she ducks away from his gaze, returning hers to the girl reassembling a rifle on her living room floor. But she can still feel the smirk he's sporting, a flicker of that rugged handsomeness flaring to life before it fades back into nothing more than an ember.
"You were decent, Castle."
He scoffs, but the corner of his mouth is twitching, his eyes flickering with amusement. "Castle?"
"Habit from work," she murmurs, but he looks all too pleased with her use of his surname, all but beams every time she calls out to him with it.
The Castles get to her, embed themselves within the walls of her heavily guarded heart after a matter of weeks, and without even realizing it, her declaration of 'for now' becomes 'forever'. As little or as long as that may be.
It's Alexis who confirms that for her.
"Hey Kate?" she whispers in the dead of the night, crawling from her sleeping bag to perch beside Beckett near the window where she keeps watch. They take turns, but she usually holds the majority of the night shift, allowing Rick and his daughter a chance to rest.
"What's up, bud?" Kate murmurs, scooting over so Alexis can share the small view of the window, the slice of glass not boarded by wooden slabs she had collected from a dumpster months ago. "You should sleep."
"I know, but I've been meaning to thank you."
"For the stale M&Ms I found down the street yesterday?" Kate muses, watching Alexis subdue her laughter while she shakes her head.
"Even though I appreciated the M&Ms, no. I meant for everything."
"Alexis, we don't need to-"
"No, you took my dad and I in after you saved our lives, you've spent the last month protecting us, teaching us to protect ourselves. Before we met you, I knew it was only a matter of time-"
"Alexis," Kate states, firmer this time, but just like the bigger of the two Castles, the little one doesn't let go either.
"I'm not scared anymore," Alexis admits, pulling her knees to her chest and propping her chin atop them. "Whether we beat this world or die with the rest of the population, I'm not afraid."
Castle's fourteen year old daughter looks to her in the pale glow of the moonlight, the ice shards of her eyes shimmering with determination, with the will to fight that had always been dormant before.
"You're going to beat this world, Alexis," Kate promises her, reaching over to squeeze the girl's shoulder. "All three of us will."
Alexis tilts into Kate's side, her head landing on Beckett's shoulder. "I hope so."
Kate hears the shift of a sleeping bag behind her, glances over her opposite shoulder to see Castle watching the exchange with soft eyes and a gentle smile. Her stupid heart flutters.
They've given her reason to fight harder; they've become her life.
They spend most of their days indoors, making runs to raid the closest stores and establishments in the area at dusk and returning before nightfall. Kate teaches him how to shoot better, fits his gun with a silencer, and does the same for Alexis. Without Kate Beckett, he doesn't think they would have made it another day, another month. She's become invaluable to him, to his daughter, to their survival. And he thinks they've made a difference in her too.
At this point in the apocalypse, the only humans left standing are the lucky - him and Alexis - and people like Kate, people who fight to the very last second, whose refusal to surrender is an integral part of their core humanity. But when survival takes over, other traits are lost - the ability to feel joy, relief, peace, or love. The guard is always up, the terror always thrumming through the veins, but over the last few months since they had met Kate, she'll sometimes lower that guard for Alexis, for him.
"We never discussed this," she whispers one night while Alexis sleeps on the living room floor, a pistol clutched to her chest, and Castle - her name for him - turns his head to her in question. "But if anything… if they ever find us, you don't let them take me, Rick. Don't let me become one of them. Don't - don't let them become me."
"Kate," he breathes, closing his eyes against the thought, the ultimate fear that always lingers in the backs of both their minds.
"You shoot me, in the head, destroy the brain. The second they get their hands on me," she instructs, her voice like steel. "Do the same for Alexis, and yourself."
Castle forces his eyes open, shifts them onto her. The apartment is dark, the risk of candles too much, but the slivers of moonlight slip in through the boards of the window, cast a glow onto her face.
"If the roles are reversed-"
"I know what I have to do," she nods, her eyes burning gold when she lifts them to him. "It makes me wish we never met, makes me wish I never…"
"I wouldn't change it," he states, firm and true, because no, even if he goes out at the hands of the extra terrestrial assholes overtaking the planet, even if he has to murder the three of them to save their lives, he would never give up Kate Beckett. Not now. "Meeting you is the best thing that happened to us since the world became theirs. Probably even before that, if I'm being honest."
She leans into his side, the two of them huddled together on the floor below the window next to her sniper's nest, presses a kiss to his shoulder.
"I don't want to die anymore," she admits, rasps, and he buries his face in her hair, cradles her skull in his palm and winds his arm around her waist to draw her in closer against him. "I couldn't just give up before, but I wanted to. I wanted to, but then you and Alexis came and now I just want-"
"We're not going to die," he promises her, quiets her as she scoffs her protest. "I have no idea how, but we've made it this long, Kate. We're surviving this thing. We will."
Kate curls her fingers at his chest, her nails snagging in the fabric stretched over where his heart beats hard for her.
"Whether we do or we don't," she murmurs, lifting her head to meet his eyes with flecks of gold shimmering in hers, a gentle smile gracing her lips. "Castle, I love you."
A flash of light illuminates the world outside, shards of white piercing through the slits in the wood boarding the windows, the building shakes beneath them, and this is it, he thinks, this is how it finally ends. With the sounds of sirens and Kate's wide eyes staring up at him.
But it won't end without him capturing her lips at least once, kissing her mouth as she gasps, giving her all he has left first.
"I love you too."
Alexis wakes with a shout and Castle calls out to her, holds her tight against his opposite side when she scrambles towards them. Both women cling to his neck, his daughter suppressing whimpers against his shoulder while the harsh staccato of Kate's breathing heats the skin of his throat, until the violent tremors ripping through the earth finally cease.
Minutes later, Kate's apartment door bursts open. All three of them raise their weapons.