I.

1924.

And I take you, to have and to hold
from this day forward—

Bucky laughs with his whole body. Steve, who lost one of his front teeth last week and is still a little self-conscious, holds up a hand to cover his mouth when he giggles, but Bucky, grinning wide, rolls on Steve's bedroom floor with the force of his cackling. Bucky is going to crumple the edges of the comic book next to him if he isn't careful, but Steve doesn't particularly mind. Bucky is seven, after all, and Steve is six (and a half, he remarks petulantly when this fact is mentioned by his mother), so Bucky is obviously more worldly-wise than he is.

"James, honey," Steve's mother says, wiping her hands on her apron as she comes into Steve's room.

"Bucky," Bucky corrects her, eyes a little accusatory.

"I'm sorry, Bucky. Your mother just phoned, it's time for you to go home." Steve knows from the tone of her voice that something has happened, but he doesn't say anything, his heels kicking out to land against the edge of his bed with a low, satisfying thud every time his foot connects. Bucky, heaving a world-weary sigh, gathers up his comic books and shoves his hat back on his head backwards.

"Here, Stevie," he says, and hands Steve the one that Steve hasn't read yet. Bucky has told him the plot, though, with his loud, excited voice and animated hand gestures, and Steve thinks he might like that better than the comic panels, but he takes it anyway and puts it next to him.

"Thanks," he says.

"G'bye, Mrs. Rogers," Bucky says, tipping his hat extravagantly, and clatters down the stairs without further deliberation. Bucky does everything like that, jumping into it headfirst, and as Steve cranes his head to watch out the window as Bucky skips down the road, he knows enough to know that he isn't like that. Steve is cautious by nature.

"Steve," Steve's mother says, sitting gingerly on the edge of the bed, and Steve looks at her through wide, blue eyes. "I have some exciting news for you."

She doesn't look excited, though, her hands knitted tightly in her lap. Steve is quiet.

"There's a doctor who says he can help you with your asthma," she says, and Steve sighs, because she has said this about many doctors, and none of them has done anything helpful so far. "I know we've tried a lot of times, and you're being such a good sport, but we need to try one more time. Can you do that for me?" She puts her hand on Steve's shoulder, her smile warm and just a little desperate, and Steve thinks about the way Bucky panics every time he draws in a shaky breath.

"Yeah," Steve says.

"We're going to go to the West Coast," she says, relief palpable in her voice. "Help me pack up your bag, sweetie, we're going to leave tomorrow."

Steve dutifully helps her pack up everything, although dread has lodged deep in his stomach. The West Coast is very far away. He hasn't ever been that far away, and neither has Bucky, worldly-wise as he is, which means that he has no one to ask about what comic books there are in the West Coast, or if the ocean looks different. Lack of knowledge frightens Steve enough that he doesn't sleep very well at all that night.

In the morning, they pile into the car to start their trek across the country. Steve is a little cramped in the backseat, but he can still see out the window, so he supposes it'll be alright—from his vantage point, hands curled into tiny fists over his knees, he watches his mother converse with Bucky, who must've come to see Steve off.

Steve realizes, with a jolt, that he will most likely never see Bucky again. He hasn't thought about that yet, and panic sets into the marrow of his bones hard enough that he can't do anything but stare, wide-eyed, at the way Bucky's hands twist around his hat. Steve's mother bends down so she can pat Bucky's cheek, and then she walks back to the car and Steve's voice cracks when he says "Mom," in his most desperate voice.

"We've got to get you well, Stevie," she says gently. "James will understand."

"His name is Bucky," Steve protests, twisting around in his seat so he can meet Bucky's tearful eyes. Steve's small hand presses against the glass as they drive away, and he doesn't look away the entire time, watching the way Bucky's left shoe scuffs over his right ankle, the way his hat is strangled in his hands. He keeps watching long after Bucky is out of sight.

2014.

"You're Lady Sif," Steve says, surprised, and gets the odd impulse to kneel out of respect; he blinks, shaking his head once to clear it. "I—it's an honor to meet you, ma'am, I didn't know to—" —Expect you, he finishes, lamely, in his head, but Lady Sif has pushed past him into his apartment and the words die in his mouth.

"I come bearing ill tidings," she says, heavily, and Steve doesn't know what's going to come out of her mouth next, but a familiar dread pangs at the base of his spine. "You may wish to seat yourself."

Steve's knees are somewhat weak, so he takes her advice. "You wouldn't come to me unless it has to do with him," he blurts out, tongue clumsy in his mouth like it is made of rubber. "With Bucky."

"Your man of ice," she says, mouth tight, and Steve's fingers curl into fists in his lap.

"Yeah," he says softly.

"Something is very, very wrong." Lady Sif does not sit, but her hand does grip her sword's hilt with a white-knuckled grasp, and this alone is enough of an admission of concern that Steve's mouth runs dry.

"You're telling me," he mumbles, painfully wry, and thinks of Bucky's dead, dead eyes behind that awful mask.

"I want you to fix it," Lady Sif says.

Steve doesn't miss a beat. "Tell me how."

II.

1934.

—for better or for worse,
for richer, for poorer—

The year is 1934 and Steve Rogers sits on the balcony with his legs dangling down over the edge. Bucky is lying down next to him, legs propped up so his feet rest on the railing, one ankle crossed over the other. Steve gets the feeling that Bucky probably would've had a cigarette dangling out of his mouth if Steve didn't have the kind of breathing problems that he has, and this thought warms Steve enough that he favors Bucky with a small, affectionate smile.

Bucky smiles back, lopsided and beautiful, and Steve feels his stomach flip.

"What're you smilin' about, then?" Bucky asks, dark hair falling into his glittering blue eyes. "See something you like?"

"Jerk," Steve says, and pokes Bucky's stomach. Bucky squawks indignantly, which makes Steve chuckle, but the anxiety that hovers always in the pit of his stomach doesn't fade. The way Bucky bats ineffectively at his hand makes it, in fact, worse.

"Punk," Bucky says, firmly, on principal. Steve ducks his head to hide a grin. "Seriously, though, Steve, what's on your mind? I'm having trouble reading it today, you're gonna have to give me a hand."

Bucky is always like this, half joke and half sincere, and it's difficult these days for Steve to tell which is which. He suspects it wouldn't bother him so much if he wasn't frightened to death of Bucky's disapproval (which he has yet to receive, but is always terrified of earning).

"Dames, I suppose," he sighs, mouth twisting as he glances back out at the sunset.

"Ooh, which one?" Bucky wants to know, scrambling to sit up excitedly. "Is it Alice Macdonald? It's Alice Macdonald, isn't it?"

"Um, no," Steve murmurs, embarrassed. "It isn't—any one of them in particular. It's kind of the lack of one in particular."

"Ah," Bucky says wisely, slinging an arm conspiratorially around Steve's shoulders. "Your soul is lonely. I've seen this look before, Rogers, and I have to tell you, it isn't a good one on you."

"Gee, thanks," Steve sighs.

"We'll find you a gal, Steve. I'm on the lookout for you, don't you worry." Bucky means this comfortingly, but the elbow that creases at the nape of his neck his heavy enough that Steve aches to the core.

"I don't really want a gal," Steve admits, and can feel Bucky's perplexed expression burn into him the way he feels the summer moonlight do the same.

"Come again?"

"I don't like any of them," Steve explains, growing steadily paler.

"There are lots of dames out there, you're gonna like one of 'em, at least," Bucky says reasonably, a touch of concern creeping into his voice.

"I don't," Steve whispers. "And I'm not…going to."

"The hell does that mean?" Bucky demands, and retracts his arm quickly, as though he was burned.

Steve's arms curl around his bent knees. "Means what you think it does, probably," he admits quietly. "I, um—"

But before Steve can finish his stumbling sentence, Bucky is shaking his head vehemently, the rest of his body trembling in sympathy. "You're not sayin' what I think you're sayin'," Bucky says firmly, and Steve shouldn't ought to feel gutted, but he does anyway. "You just aren't, Stevie."

Beautiful words are gorgeous when they fall from Bucky's tongue, and ugly words are hideous; transitive property of importance, Steve supposes. Bucky's vehemence is the one thing that lends reality to a situation in which Steve is fairly certain he's resided too long in denial.

"Well," Steve says, wetting his lips with the tip of his tongue, darting a glance over at Bucky. "Now I'm not, I guess."

Bucky watches him for a long minute, eyes just barely edging on hunger, and for one frightened heartbeat, Steve is convinced Bucky is going to kiss him—

"I need to smoke," Bucky mutters, already digging around in his pocket for his lighter as he stumbles to his feet, and all but flees off the balcony and down the stairs. Steve lets his forehead fall against the railing, doesn't watch him leave, and squeezes his eyes shut.

A few days later, Bucky finds him, and although he's smiling, the expression is just that little bit too bright. He doesn't talk about what Steve almost said, and although Steve is a little relieved—Bucky has never actually hurt him before, and he likes to hope it's going to stay that way—the casual touches that had sustained him previously dry up. Bucky no longer drapes his arm around Steve's shoulders, no longer presses his ankle against Steve's and lets it stay there.

It is such a loss that Steve finds himself pressing the heel of his hand over his sternum in the dead of night, aching, trying to keep every inhalation from being a gasp.

2014.

"You're telling me there are—alternate realities." Steve has watched enough sci-fi at Tony Stark's insistence that he understands the concept well enough, but he isn't sure what that has to do with the world he's living in now. "And I have to…I'm so sorry, you're going to have to explain it again."

Lady Sif sips unhappily at the coffee Steve pushed toward her. "On occasion, the universe in which you reside and the universe in which I and my people reside is known to…misalign."

Steve blinks. "That doesn't sound good," he suggests cautiously.

"It isn't," she agrees solemnly, and she looks now more than ever that she has lived for hundreds of thousands of years, that she has watched an uncountable number of stars bloom into existence and fade back into the ether afterward. Steve had thought he was old. He knows now he is wrong. "There are grievous side effects. The misalignment, it is—pushing you and your companion apart."

Steve's stomach drops. "I thought that was HYDRA."

Sif smiles slightly, pained. "I am afraid I was not clear enough. In every universe. You are being pushed apart in every single one."

III.

1940.

—in sickness and health,
to love and to cherish;

When Bucky stumbles through the door, drunk, lipstick smudged over his collar, Steve isn't particularly surprised. He isn't pleased, either, but he closes his book dutifully to quirk his eyebrow in Bucky's direction.

"You look like you had fun," he says, pointedly looking at the red mark smeared over the curve of Bucky's throat.

Bucky shrugs noncommittally. Steve can smell the whiskey on him from ten feet away. "She was alright," he sighs, and falls onto the couch next to Steve, scrubbing his hands over his face.

Bucky's arm, when it falls over to rest the back of the sofa cushions, lands in such a way that his fingertips just barely brush over the nape of Steve's neck. Steve knows this dance that they do, knows it deep in the marrow of his bones, but it doesn't stop his heart from racing still, his pulse pounding alarm through his veins.

"Well, Annie'll keep coming back to you, like she always does," Steve says, forcing levity. "You can try again tomorrow."

Bucky gives up any pretense of distance and curls his body close to Steve's, pressing his face into the crook of Steve's neck. "Doesn't it get lonely?" he murmurs against Steve's throat. "You all by yourself over here, waiting up for me until the early hours of the morning?"

"Don't flatter yourself," Steve says unsteadily, though one fist curls around the back of Bucky's jacket. "I was reading a really good book."

"Bullshit," Bucky snorts, mouthing over the hollow of Steve's throat, teeth scraping over Steve's adam's apple in a way that makes Steve shudder as warm, broad hands slide over Steve's waist. "You're a filthy liar, Rogers."

Steve can smell the woman's perfume clinging to Bucky's hair and it ignites something possessive and ugly in the pit of his stomach. He grabs a handful of Bucky's hair and yanks him into a kiss that Bucky whimpers into, crushing Steve close, whiskey on his breath and on the curl of his tongue.

When Bucky pulls him into his lap, Steve doesn't even care that they're on the couch, lets Bucky wriggle them both out of their clothes with graceless enthusiasm that Steve refuses to find endearing, even though it is a warmth deep in the pit of his stomach. Bucky slides slick kisses from Steve's jaw to his throat to across his collar bone, their hips slotting together as if they were designed to align, and when he wraps a hand around the both of them, wrist twisting exactly right, Steve kisses him again to stifle the way he cries out.

"I hate this," Steve pants against Bucky's mouth. "The women, I hate this—"

"Shut up," Bucky mumbles, not unkindly, and even though the edge of his jaw is marked with a woman's caress, his cock is hard as it presses into Steve's hip, and that is nearly enough. Steve rocks his hips against Bucky's, grinding down, and the wet, open-mouthed gasp this pulls from Bucky makes him smile tightly.

Steve slides off of Bucky's lap and doesn't miss the whimper from Bucky, though if it's from the loss of Steve's body on top of his or the loss of friction on his hard-on, Steve isn't masochistic enough to guess.

"You didn't get this far with her?" Steve asks, quirking an eyebrow as he settles between Bucky's knees.

"C'mon, punk, you know I didn't," Bucky mutters, looking away.

Steve lets Bucky wind his fingers in his hair as he takes him into his mouth. They have done this so many times—Steve knows exactly how to twist his hand around the inches he can't take, knows the spot to rub his tongue to make Bucky groan low and rough from the back of his throat. Bucky hisses nonsensical things between his teeth ("Should be me on my knees, fuck, Steve, your mouth—") and Steve sucks harder, gazing up at Bucky through his eyelashes.

It doesn't take long. A well-timed drag of his tongue up the underside, swirling around the head, and Bucky's hand tightens convulsively around his fistful of Steve's hair as he comes. Steve pulls off with a gasp, pink-flushed, lips red, and strokes Bucky through it with a longing twist at the base of his spine. Bucky, who is glassy-eyed, and looks at Steve as though he can't quite believe what he's seeing, hauls him back up into his lap with desperation stinging-bright on his tongue when he kisses him. He jerks Steve off fast and rough, whispering dirty things in his ear that Steve will probably blush thinking about in the morning ("You're gorgeous like this, do you know how much I want to fuck you? Your mouth is fucking ridiculous, I can't get it off my mind—"), and all Steve can do is feel his hips stutter as he winds his arms around Bucky's neck.

"C'mon," Bucky all but growls, biting down on Steve's shoulder, and that's all it takes. Steve shudders in Bucky's arms, pressing his face into the crook of Bucky's neck as he falls apart.

Later, when Bucky has pulled Steve close to him as they lie in Bucky's bed, Bucky traces his fingertips over whichever part of Steve is nearest—his shoulder blade, his rib cage, his thigh—and Steve wonders, vaguely, if he will always qualify his body with the terms of where Bucky has touched. Here, Bucky has ruffled his hair affectionately, here, Bucky has dabbed disinfectant over a scrape blooming over Steve's cheekbone, here, Bucky has slung an arm around his shoulders as though he and Steve are the only two friends alive in the world, here, Bucky has traced over Steve's spine again and again as Steve lies sick in bed, thumb catching on the dips between his vertebrae. Here, Bucky has kissed the soft skin between Steve's thighs.

Steve listens to the way Bucky breathes, despair panging in his heart, and knows that it isn't much of a question, not anymore.

"I'm gonna have to marry her one of these days, y'know," Bucky murmurs. Steve squeezes his eyes closed.

"What then?" he asks quietly.

"Then we'll…live on the same street," Bucky says, after a moment, though it sounds like it pains him. "And our—our kids're gonna play with each other."

"Fuck," Steve mumbles, and presses his face into his pillow. Bucky's hand slips off his shoulder.

2014.

"How am I supposed to fix alternate universes?" Steve asks, bewildered. "I don't even know how to fix the one I'm in right now. He won't—I don't know where he is."

"It will be dangerous," Lady Sif says, lower lip scraped between her teeth.

Steve ducks his head to hide an expression somewhere between a wince and a smile. "Dangerous, I'm used to," he says softly, dryly.

"You're not used to this kind of dangerous," Sif says, eyes sharp. She can't seem to stop worrying her lower lip between her teeth, over and over again, and it puts Steve on edge.

"Ma'am," Steve replies, wetting his lips with the tip of his tongue. "I'm not quite sure you understand. I'd die for him. Hell, I already did, once. I'd do it again in a heartbeat."

"You very well might," she says, and Steve knows it's wrong, but he can't fight the rush of adrenaline that slicks through his veins. This, he can do. He can die for Bucky. He knows the way this play pans out, and although the world around him is made of broken bones, Steve knows as deep down as his genetic makeup how to die for Bucky Barnes.

"Just tell me when," he says, smiling around a mouth full of shrapnel.

IV.

1943.

From this day forward—

Peggy warned him, before he jumped out of the plane, that he'd most likely find Bucky dead. Now, as Steve tears through the hallways of the HYDRA base, he's only just starting to agree with her; he has been Captain America for months, but has never once felt the weight of that name pressing between his shoulder blades the way he does now.

He can no longer feel his breaths burning through his lungs the way he did when his body had been weak and riddled with a thousand potential deaths under his skin, and it still surprises him that he doesn't just drop from exhaustion anymore. He's sent the other prisoners out already, and he can hear the battle raging on outside, but nobody has seen Bucky, and that is who he came for. That's how it always is, anyway, Steve following Bucky into trouble, into danger, and now, impossibly—into war. Steve has the presence of mind to wonder uncomfortably what Bucky will think of him, when he sees him now.

Steve knows, the moment that he sees the door ahead of him, that Bucky is inside. Later, he will marvel at the fact that he knew; was it his enhanced supersoldier senses? Was it one of those gut impulses he's always told himself to follow?

Was it the fact that his and Bucky's hearts call to each other like satellite signals?

Whatever the reason, when Steve skids to a stop in front of the door, he knows what he will find. And this inhalation—this inhalation burns anyway despite his new biology, makes him cling to the doorframe until it cracks between his fingers.

"Oh, god, no," he breathes, but there is no one to hear him.

He battles his way out of the HYDRA base one-armed. Bucky's body is slung over his shoulder—it will never get any easier, thinking Bucky's body instead of Bucky—and when he and the other prisoners walk back to base camp, Steve does not allow anyone to touch the man in his arms, whose had lolls to rest on Steve's collar bone, whose skin is like ice beneath his cheek. Steve carries Bucky all the way home and he does not cry, even when Peggy touches his arm and tells him it isn't his fault. (It is a near thing, though, when Colonel Phillips looks at him with eyes kinder than Steve has ever seen them.)

I'm with you 'til the end of the line, pal, Bucky had always said, as though it were a prayer on his lips instead of a promise, but Steve hasn't held up his end of the blood pact. He almost can't believe that it isn't visible, that the betrayal he committed is not stained on his skin, but he supposes almost bitterly that the mark of Cain can't touch Captain America.

When he is alone at last, the noises he makes are not tears, but they are animal noises, and he makes them into the palms of his hands.

2014.

"You will have to go to him in every universe. It might be—difficult to find him." Sif has sketched out a diagram of the way the device works, but both her magic and the technological equivalent in the 21st century leave Steve stupid and stumbling.

"Once I find him, then what?" Steve asks, and it is not only a pulse that pounds in his ears, but also something heavier, like thirst. Like fear. Like, perhaps—as dangerous as it is—hope.

"Well," Sif says, and scrapes her hair out of her eyes. "You will have to fix it."

Steve thinks about the Winter Soldier's shrapnel eyes and knows, in the deepest part of his bones, that if he can't fix Bucky now, then he cannot possibly fix him in all the other universes out there. He knows with equal certainty that he will die trying, if he has to.

"If Tony Stark's constant babble is at all correct," he says, frowning as he rubs a hand over his jaw, "I've heard him say there's an infinite number of—parallel universes. It won't be possible to find and save every version of him."

Sif smiles. It's the first time Steve has seen her smile this entire time, and it relieves him a little, even though his spine feels somewhat as though it has been numbed by kerosene.

"At some point," she says, quiet with conviction as she rests her elbows on her bent knees. "The misalignment will start to heal itself, with your help, and your friend—your man of ice—will start to want to come home to you."

"Oh," Steve says, faintly, and realizes that he has been operating under the premise that Bucky will never come back to him for so long that it leaves him breathless, thinking he could live in a world where that assumption is false.

"Tell me again how the device works," he asks, hope blooming in starbursts behind his collar bone.

Sif reaches for her pen.

V.

1945.

—Until death do us part.

"Better get moving, bugs," Dum Dum announces grimly with a wry twist to his mouth, and Steve steadies himself with a breath before he goes down the zipline. The wind slices at his face, but he doesn't really mind; the chill can't hurt him now that his body has bloomed into something foreign, and he lands on the top of the train with only the smallest jolt of fear down his spine.

"Here we go, Rogers," Bucky murmurs, and Steve nods, touches Bucky's neck once before they stow inside the compartment.

The battle, for all its ferocity, is brief, and Steve only feels real fear the moment the doors close between him and Bucky. Bucky waves him on, determination clenching his jaw. Steve can see his own helplessness in his reflection in the glass.

Still, there is a HYDRA agent at the other end of the room dressed up in more weaponry than Steve thinks is frankly fair, and Steve knows how to focus on doing what has to be done. He has faced worse at the hands of Brooklyn bullies, has felt his weak bones crack too many times to fear it anymore, and beats the HYDRA agent into submission with the single-minded determination that came with the knowledge of Bucky's entrapment on the other side of the door.

He opens the door with fumbling fingers and tosses his gun into Bucky's waiting hands, his shield feeling somewhat useless at his side. Bucky hadn't been surprised to learn that Steve uses a defensive tool for an offensive weapon; he'd sighed a breath through his teeth, rolling his eyes as he ruffled Steve's hair, but he hadn't been surprised in the slightest. Steve wonders if that's because Bucky thinks he's good at defending himself, or that he thinks Steve wouldn't like to use a gun—both are true, but Steve knows as he has always known that Bucky's interpretation is better.

The HYDRA agent Bucky is fighting has a gun that does not shell out bullets. Steve notices the odd blue glow as it whistles past his ear, and it sends something dark and a little like terror into the heels of his hands and the balls of his feet.

He tosses his shield to Bucky with a strained noise of panic, and Bucky catches it easily, holding it in front of himself awkwardly as he fires off three rounds into the advancing agent's head. Steve finds the choked-off sound the agent makes—a far cry from Hail HYDRA—to be sickly satisfying, and then mentally berates himself for taking pleasure from someone's death. This was a person, he reminds himself sharply, watching the blood pool under the agent's skull. This was a person who tried to kill Bucky, he adds musingly after a moment, which makes him less sympathetic.

"I had him on the ropes," Bucky rasps, voice rough from exertion.

"I know you did," Steve replies, not unaffectionately, and takes his shield back. There's no time to kiss away the ghosts in Bucky's eyes, though, not even time enough to curl his fingers around Bucky's wrist, because the enormous guard from before with his body entombed in machinery has staggered toward them to blow a hole in the side of the train with a sound like a thunder clap.

This time, the whistling air that Steve feels against his cheek chills him to his bones.

"Bucky—" Steve says, warningly, but Bucky has already scrambled for the fallen HYDRA agent's gun and has raised it to eye level, and Steve leaps between the gunman and Bucky's body to shield them both from enormous blue bolt of energy that hurtles toward them. As soon as the bolt of blue lightning has ricocheted off Steve's shield, Bucky whips the gun over Steve's shoulder and fires once, twice, three times with the strange HYDRA weapon he stole, and the gunman falls—but not before firing a round that hits Steve in the chest and sends him flying out the hole of the train.

Steve screams Bucky's name, clinging to the railing that bends away from the train. His legs flail out behind him. Bucky is reaching for him, but Steve knows with growing dread that it isn't enough.

"Take my hand!" Bucky hollers, pushing his hand out as far as it can go. Steve reaches for him, straining, but the metal holding him to the side of the train is straining too, and it does not have Steve's determination to hold on. With a crack like shattering bone, the metal breaks, and Steve hurtles toward the ground with Bucky's wail in his ears.

2014.

"How far back are you going to send me?" Steve asks, while Sif is rummaging through her knapsack to find the pieces of her machine. It lies on the table, half-formed, a skeleton both in idea and formation, and Steve imagines it strapped to his back with a shudder. It glows vaguely. Steve supposes it's her magic, but it reminds him of HYDRA anyway.

"Well, I suppose that depends entirely on when things began to go wrong," Sif says distractedly.

"Oh," Steve says. "Far, then."

Sif buckles a contraption onto Steve's wrist that reminds him vaguely of a wristwatch. "What's this?" he asks, though he is weary enough that he wonders if it's wise to ask.

"This," Sif says, tapping the face of the watch more firmly into place, "Is what will tell you the manner in which the two of you are being separated."

"Helpful," Steve comments, and is glad he asked. "When will I know I've done enough?"

"When you wake in this universe with him beside you," Sif answers promptly, with more faith, Steve thinks, than she actually feels. Or at least more than he deserves.

VI.

2014.

I do.

They bury him with his mask on. Steve isn't there when it happens, he has HYDRA to defeat and a world to save, after all, and one fallen soldier with a metal arm shouldn't obsess him. The Winter Soldier doesn't cross his mind often, but when he does, Steve only thinks about his eyes, about the way they were empty, echoing. Haunted. Steve catches himself wishing that those goggles had never come off, just so he never would have had to see the way those crystal blue eyes looked as though they were nothing but broken glass.

He tries to put it out of his mind. He has bigger fish to fry, metaphorically speaking, and he supposes he's just glad that Natasha gets some closure, after having the threat of the Winter Soldier's wrath hanging over her for so many years.

He has a compass in his pocket. Bucky's face is inside, and it stays there, directly over his heart, destined to remain there long after the war with HYDRA is over. The real War is never over, after all; it is what Steve's cells were rearranged to create, it is the only thing that Steve has left to live for. It will also outlive him, as much as Steve's body was rewritten for violence—he wonders, vaguely, if it should concern him that he has written out the rest of his story already, and that it comforts him to know that he will not die an old man.

2014.

" There is no guarantee that this will work, you know," Sif says, her lower lip scraped between her teeth once more. Steve finds himself silently bemused by the fact that he's learned her nervous habits in the brief period of time he's known her. Bucky is the one who can read people, after all, and Steve has always relied on him to do so. The fact that their relationship is changing even with Bucky an entire eternity away makes Steve cringe, a little, as though the scalpel of time struck bone.

"Just press the button," Steve says, as gently as he is able—which is not, altogether, all that gentle—and twitches under the cool press of metal on his back.

I.

1924.

I take you to be my constant friend, my faithful partner
and my love from this day forward.
In the presence of God, our family and friends, I offer you—

Steve is lost in his own city when he stumbles, leaning against the nearest brick house as Sif's machine on his back weighs him down until his knees give out beneath him. He allows himself five deep, achingly familiar breaths of Brooklyn air before scrambling to his feet to find Bucky.

The black-haired child with accusatory eyes is not what he expects, but he is defiant enough that he is unmistakable.

Steve kneels solemnly and presents him with an address, the name Steven Rogers printed as neatly as he can in his loopy handwriting at the top of the page. Bucky, suspicion overwhelmed by something a little brighter, snatches the paper and bolts for the doorway. Steve grins after him, the device around his wrist buzzing warning into his skin before he's yanked away again into a different reality.

II.

1934.

—my solemn vow to be your faithful partner in sickness and in health,
in good times and in bad—

Steve appears on the pavement in just enough time for a teenage Bucky Barnes to slam into him full force.

"Shit, I'm sorry," Bucky yelps, and Steve is grateful he isn't sent sprawling. Bucky dropped the cigarette he'd ben holding in the brief altercation, and Steve watches him look at the collateral damage longingly before turning back to him. "Alright?"

Steve rubs his shoulder, equally bemused and unoffended. "I'm fine," he says, and something about the way he says it makes Bucky pause, head cocked with suspicion sparking in his eyes. "I was—looking for you, actually. Bucky, right? Bucky Barnes?"

Bucky stiffens. "Depends on who's asking," he says, and juts his chin up defiantly like he thinks he's in the movies or something.

Steve lets out a laugh, ducking his head to ineffectively hide the way his smile curls his mouth. "I'm one of Steve Rogers' neighbors," he says, because the truth isn't a thing he can prove easily, and this Bucky—like, Steve suspects, most Buckys—is suspicious enough of him already.

Bucky flushes pink with embarrassment. Steve can see the sheepish, familiar twitch of his left shoulder as he rubs a hand awkwardly over the back of his neck. "Jeez, I'm sorry. Yeah, I'm Bucky," he says, and sticks his hand out for Steve to take.

"Grant," Steve replies, accepting the hand with a small smile. "I heard raised voices," he adds, after he releases Bucky's hand. "Everything alright?"

Bucky shrugs a shoulder, digging around in his pocket to retrieve a cigarette to replace the one he lost in the scuffle. "Oh, y'know," he says, shrugging fluidly with his cigarette between his teeth. "Moral differences. Say, gotta light?"

Steve retrieves a box of matches from his pocket, striking one and holding it out for Bucky to lean the tip of his cigarette into the flame. It's dark out, but even with the night-time enveloping them both in its black embrace, Steve can clearly make out Bucky's face, and it does something strange to the pit of his stomach. This Bucky hasn't lived through what he will later—he and Steve are nearly a century apart in age, which makes Steve cringe to think about—and weariness hasn't been written into the lines of his face. Not yet, anyway, Steve thinks grimly to himself, which is uncharitable. The future for this world could be a thousand different things.

"Little young for heavy smoking, aren't you?" he asks, shaking the match to put it out.

"I'm growin' up fast," is all Bucky says, shrugging.

Steve exhales in a startled laugh, and doesn't say anything for a long moment. Bucky's eyes, reflecting the red glow on the end of his cigarette, do all the talking for him.

"He wants what you want, you know," Steve says, eventually, and watches Bucky very nearly drop his cigarette again.

"Excuse me?" he demands, looking at Steve with a mouth full of rage that Steve has only rarely seen before. Steve holds up his hands in surrender, but there is no trace of surrender in his shoulders, in the way his mouth tightens. "You aren't Steve's neighbor," Bucky says, unsteadily. "Who the fuck are you?"

"He wants what you want," Steve says, again, aching. "I—I would know, Buck, okay? Do me a favor and trust me, will you?"

Bucky's shoulders tighten, back ramrod-straight. "Fuck off," he mutters, though Steve has known him long enough to tell from his posture that he doesn't mean it.

"People like you," Steve says, quietly, like it pains him, "Can get married, where I come from. In the future. It isn't wrong, Buck. I promise."

"Bullshit," Bucky breathes, leaning back onto his heels, almost reeling.

"Trust me," Steve repeats, trying with every fiber of his being to keep desperation out of his voice.

"Give me one good reason," Bucky rasps. His cigarette burns, ignored, between two of his fingers.

"You know me," Steve says, a touch desperately despite himself, scuffing a hand through his blond hair. "Isn't that reason enough?"

Bucky swallows, meets Steve's eyes with his own filled with the constellations up above their heads, and nods, jerkily.

2014.

"Does it always feel like this?" Steve gasps, breathless, beads of sweat rolling down his spine. Sif is calibrating the device again, and Steve waits as patiently as he is able for her to put it between his shoulder blades again.

"Like what, friend Rogers?" she asks absently, and twists a piece of metal into place until it sparks gold.

"Like I'm being turned inside out," he says, the feeling of Brooklyn's city streets still pulsing like a fever at the balls of his feet and the heels of his hands.

Sif looks at him for a long moment. "Yes," she answers. The gold glow reflects off her eyes.

III.

1940.

—and in joy as well as in sorrow.
I promise to love you unconditionally, to support you in your goals—

This Bucky recognizes him, and the look of panic on his face is almost comical when Steve shoves him against the brick wall of the alley.

"You can't have everything," Steve snarls. "He's never going to say no to you."

"How—" is all Bucky seems able to say, hands coming up to rest on Steve's shoulders. He is mouthing Steve's name over and over again, although if it's a prayer on his lips or a curse, Steve can't tell. "How—"

"It doesn't matter," Steve snaps, desperation tightening his grip on Bucky's lapels. "What matters is that I'm here. And I'm here because you are fucking up."

"That's ain't—that ain't fair, Steve," Bucky manages weakly, eyes flickering off of Steve's face to land on their feet, on Steve's scuffed-up shoes. The machine on Steve's back is heavy between his shoulder blades, but he thinks it must be dread that is pressing down on his spine. There isn't anything else heavy enough to make his shoulders curl.

"You're right," Steve said quietly. "It isn't fair. It's not fair to him, it's not fair to you, and it sure as hell isn't fair to that poor girl you're stringing along, Buck."

Bucky is silent for a long, taut moment before he crumples, as though someone has cut the electrical feed to his spine. His forehead hits Steve's collar bone. His breath is hot and unsteady against Steve's neck.

"I didn't think I was this drunk," he mumbles, and Steve notices for the first time the mostly-empty bottle that hangs loosely from one of Bucky's hands, the one that looks like it's very much in danger of falling if Bucky isn't careful. "Look, if you're a figment of my imagination, y'could at least be on my side."

"Call me your conscience," Steve says, wryly, and curls a hand around the back of Bucky's neck, just to feel the warmth coming off his skin. Steve has to keep his eyes from meeting Bucky's—he knows that he can't be trusted not to hang onto him too long if he can see him, because he's human, and because this Bucky is the Bucky he remembers best. (The one he presses his face into his pillow and imagines, back home, shoulders shaking—he has not met a Bucky that he hasn't mourned, but this Bucky, hair slick and tie loose, this is the Bucky that Steve keeps around his neck with his dog tags. Sometimes he wonders if the Steve of this era, all rib bones and healing bruises, is the Steve that Bucky missed most.)

"I am on your side, you know," he adds softly, after a moment, his cheek pressed to the crown of Bucky's head. It aches, being this close to him, but Steve can't bring himself to pull away. "There ain't a world in which I'm not on your side, Bucky."

"And that's the problem, ain't it?" Bucky mumbles, leaning out of Steve's embrace to let his head fall back against the alley wall. "But I'll—I'll fix it."

Steve's wrist starts buzzing. "There's a thing you should tell him," he says, quickly, because he's running out of time.

"What?" Bucky still has a hand curled around the material of Steve's shirt.

"Tell him you're with him 'til the end of the line," Steve says, and vanishes.

2014.

Sif doesn't ask him how well the operation is going. He expects her to, but all she does is take the smoking machine off his back and tweaks the wires, fixing it with her strange glowing magic until it lets off its gold light again.

"So the machine takes me back when it gets broken?" Steve asks curiously, panting from the journey between realities. He's curious, but he also is growing tired of how loud his head is getting. Sif's voice can distract him from the gunfire screaming between his ears.

"Yes, it returns you to your original timestream. Call it a failsafe." Satisfied, she holds up the device again. "Back to thy mission, Captain."

"Funny you should call it that," Steve says, mostly to himself, and shrugs the metal onto his back once more.

IV.

1943.

—to honor and respect you,
to laugh with you and cry with you,
and to cherish you—

Sprinting through the HYDRA base is something that Steve has had nightmares about for years. He's relived it enough times in his dreams that he knows the twisting-turning of the hallways like the back of his hand, can mumble the directions to himself while he turns left, right, left again, boot heels striking the floor with an audible noise every time.

This Bucky is out of it enough when Steve finds him that he doesn't worry too strongly about being remembered; he slides an arm around his waist, supporting his weight, and doesn't flinch when Bucky paws at his collar, fingers curling into a fist around the fabric of his shirt.

"The fuck did they feed you while I was away?" Bucky rasps, blinking a little too quickly. Blood, Bucky's blood, drips down onto Steve's sleeve. He's going to bleed out if Steve doesn't do something quickly, so Steve props him up against the doorway and rips off his own shirt, fumbling a little as he tears it into bandage strips with his teeth.

"Try not to talk," he says, and gives Bucky the best smile he can muster, even though he's certain it is unconvincing and perhaps even a little watery. "You sound like you swallowed a pack of cigarettes whole."

"And you look like a fuckin' Greek god," Bucky complains, wincing as Steve bandages him up as best he can. "But I wasn't gonna say nothin'."

Steve laughs, startled, and doesn't protest when Bucky leans on him close enough to feel his hot breath on his throat, lips dangerously close to his racing pulse. "We gotta get you out of here," he says, unsteadily, holding Bucky upright.

"I better get my 'hello' kiss after we get out of this hellhole," Bucky mutters, and then he and Steve are, miraculously, stumbling back toward the entrance. Steve counts Bucky's heartbeats against his forearm as they walk, and is relieved to find that they are fairly even. It really had been a matter of timing, then, finding Bucky alive; he is reminded with a sick twist in his stomach of how easy it would have been to lose his Bucky—if he'd been a little slower—

Bucky clutches at his shoulder. It's a moot point, anyway.

"Steve?" Bucky asks, his head lolling onto Steve's shoulder as they walk, stumbling feet knocking together.

"Yeah, Buck?" Steve clutches him closer, tries not to look at the ashen-paleness of Bucky's face.

"Assuming I'm not hallucinating this whole thing," he mumbles, tightening his grip on Steve's bicep. "We're gonna have a serious discussion about your height. It ain't right, you bein' taller than me. I don't like it."

"Wasn't your choice," Steve says, though he's smiling.

It's when they turn the corner again at the end of the hall—Bucky mumbling half-formed words to himself, eyes half lidded, mouth half parted—that Steve very nearly runs smack into himself. He hasn't encountered the Steve Rogers of any alternate universe so far, and it unnerves him enough that he unconsciously shifts Bucky behind his body protectively.

The other Steve's eyes flick from Bucky's shuddering shoulders to Steve's hand curled around the back of Bucky's neck. Did I ever really look like that? Steve thinks to himself, bemused. So goddamn young?

"Take him," he says, and carefully puts Bucky in the other Steve's arms. "And run."

The other Steve waits only a heartbeat before nodding, though he hesitates. "Do I want to know who you are and how you got here?" he asks carefully.

"No," Steve answers honestly.

"Alright," the other Steve says, and runs.

2014.

Sam is there when Steve gets back this time, shivering, sweat soaked, and he puts Steve's head in his lap while Steve's teeth chatter in his mouth.

"Fever," Sam says grimly.

"Bucky," Steve whimpers.

"Is he supposed to get like this?" Sam asks, frowning, and Sif puts her hand on Steve's forehead. The warm gold glow that she infuses in the machine pulses over his forehead, easing the tremors in Steve's spine, enough that he presses his face into Sam's leg, gasping in relief.

He sleeps like the dead for seven hours. Sam is still there when he wakes up, eyes concerned and kind, and Sif is sitting in the chair across from the couch Steve is lying on. "I apologize, friend Rogers," she says, quietly. "Thy journey is taking its toll."

"But I'm not done yet," Steve says, wryly, and pushes himself up out of Sam's lap with a groan. "Sorry for sleeping on you, buddy." He pats Sam's shoulder blindly while rubbing a hand over his aching eyes.

"Are you sure about this one?" Sam asks him carefully. "You're looking a little raw at the edges, man."

"Sam," Steve says, patiently, while he takes the device from Sif again. "I'm just a little tired, that's all."

Sam makes a dubious noise.

Steve shoulders the machine, letting it click into place around his neck and down the backs of his arms. "It's Bucky," he explains, shrugging.

Sam sighs. "Do me a favor and don't die or something, will you?"

"Is that how it is?" Steve asks, arching an eyebrow.

Sam rolls his eyes, smiling with exasperated fondness. "Oh, that's how it is."

V.

1944.

—for as long as we both shall live.

Steve finds Bucky in the bar, and nearly cannot force himself to cross the threshold. When he steels himself up to do so, his boots crush broken glass into the floor, making him wince. Bucky is sitting with his back to the shattered windows, head bowed forward, and Steve is struck, as he always has been, by the paleness of his skin. If Steve were anyone else, he would've thought Bucky was spun glass. He knows better—Bucky is shrapnel, not glass—but the image stays.

"Hey, Buck," he says quietly, and stuffs his hands in his pockets. He'd thought about it often—if their situations had been reversed, if he had fallen off the train instead of Bucky—but he'd never expected to be pushed face to face with a Bucky for whom the situation is not hypothetical. When Bucky raises his red-rimmed eyes to meet Steve's, the hope that blooms and dies behind his open eyes is sickening.

"Am I dreaming?" he rasps, clutching his half-empty glass in a white-knuckled grasp.

"Yes," Steve answers, because it's easier than explaining that he is a multi-dimensional time-traveler who could disappear at any moment.

"Okay," Bucky says, and drains his glass.

With their timeline so fucked up, Steve has no way of predicting the future. Will this Bucky crash the Red Skull's plane into the ocean? Will this world's Steve Rogers get captured by Zola? Will this Bucky have to watch the Winter Soldier's mask get torn off, only to be confronted by Steve's face?

More importantly: if this is Bucky's future, how the hell is Steve supposed to comfort him?

"I can't stay long," Steve says, and sits gingerly on one of the bar stools, after brushing glass shards off the seat. Bucky nods, watching him with hungry eyes, as if drinking in every twitch of Steve's lips, memorizing the way Steve's hair swaths over his forehead. Steve can recognize this expression because it is the one on his face whenever he sets foot inside the Smithsonian museum. "I'm sorry."

"For what?" Bucky demands, and slams his glass onto the table. "For what, Stevie, huh? For going out like the goddamn hero they said you were? For not reaching my fucking hand?" There is something wild in his eyes that Steve is not certain he is familiar with. This Bucky is a foreign object to him in grief; Steve does not know the way his fingers curl, he does not understand the convulsing of his throat. He does not want to understand. He also does not know how Peggy Carter could have stood to be in the same room as him, if he wore that same terrible expression the day after his Bucky died.

"I'm sorry I'm not here," is all Steve says, and it is not even within arm's reach of enough, but it is something, and it makes Bucky's face screw up with an emotion for which Steve does not have a name.

"Shut the fuck up," Bucky says, and stands up. He almost stumbles over, catching himself on the back of his chair, and Steve doesn't reach out to catch him, but the impulse to do so hammers through his veins. Bucky staggers toward the bar, reaching for a new bottle. Steve hands it to him. "What's the point?" Bucky asks, eyes concentrating on pouring without spilling down the sides. His eyelashes, Steve notices, are wet. "Without you. There ain't a point, pal."

"Of course there is," Steve protests, heart aching as though Bucky has reached between his ribs and crushed his fingers into a fist around it. "Bucky, you aren't just here for me."

"That's exactly what I'm here for, asshole," Bucky laughs, the sound like metal scraping over glass, and throws back this drink with a grimace. Bucky has never been a heavy drinker. Steve wonders how long he's been sitting in this bar already, trying, desperately, to scrape the images of the train off his eyes. About as long, Steve suspects, as he did.

"Even if that's true—" Oh, god, please don't be true. "—That isn't why you're here now."

Bucky watches him mutinously. "Oh yeah?" he asks, voice rough.

"Bucky Barnes," Steve says, desperately, and reaches out to curl his fingers around both of Bucky's wrists. "You're going to save the world. And you're going to do it by any means necessary. Schmidt didn't suddenly give up because I—" He swallows. "Because I died."

Bucky's eyes flick back and forth between Steve's. "What are you saying?"

"Take up the mantle," Steve says, suddenly inspired, and strokes the pad of his thumb in circles over Bucky's knuckles. "Become Captain America."

"Fuck no," Bucky breathes.

"For me," Steve says, swallowing down the spark of electricity that crackles down his spine. "Please."

Bucky's mouth opens and closes, but no words come out. Steve keeps hold of his hands, wetting his lips with the tip of his tongue, and traces meaningless patterns into the palm of Bucky's left hand with the tip of one forefinger. He can see it when Bucky's resolve crumples, and he hates himself for knowing not to catch him before he falls so that Bucky's face ends up in the crook of his neck.

"Gonna miss you," Bucky mumbles, lips dragging over Steve's skin, almost directly over his pulse.

"We're going to end up in the same place, anyway," Steve says, consolingly, and thinks of the 21st century, of the bright future Bucky has yet to see.

"Heaven?" Bucky asks dubiously, and doesn't lean back. Steve lets him.

"Sure, Buck," is all he says, quietly, and rubs his hand reassuringly over Bucky's back.

VI.

2014.

I do.

Steve has forgotten, somewhere in between timestreams, exactly how much it hurts to see those dead, dead eyes peer at him from beneath his dark fringe. For one horrible, sick heartbeat, they are both still, electricity crackling between them like white noise. Then the Winter Soldier breaks it with a growl, and Steve has to raise his arms defensively to keep his eyes from getting gouged out.

"Bucky—" Steve tries, dodging a metal fist to the head that slams into the brick wall behind him.

"That's not my name," the Winter Soldier snarls, panicked, and Steve gets a lucky hit to his stomach with the heel of his foot, sending the Winter Soldier flat on his back onto the concrete. Steve follows quickly, pinning the Winter Soldier's wrists above his head, and tries not to think about the body underneath him, because that is disgusting, and because Bucky doesn't deserve Steve wanting him while he is made of ice.

"Listen to me," Steve says, but the Winter Soldier has other ideas. He wrenches his metal wrist out of Steve's grasp, wrapping his fingers around Steve's throat to slam him onto his back. Steve hears the machine on his back grind into the asphalt, and panic strikes his heart like a live wire so hard that he can taste electricity on his tongue. His body flickers like radio static, and the Winter Soldier reels back far enough that Steve can breathe.

Oh, Christ, he thinks, desperately. I'm going to be sent back too early.

"Who are you," the Winter Soldier hisses, his metal hand hovering over Steve's body as though he is afraid to touch him.

"My name is Steve," Steve said, quickly, because his own hand is blinking in and out of existence in front of his eyes, and that is most definitely cause to panic. "Steve Rogers. You—you know me, and I know you won't want to, but you have to find me—" His whole arm goes this time, and he flinches, even though he feels no pain. There is something deeply disturbing about losing a part of his body right in front of his eyes. (His eyes catch on Bucky's metal arm and he winces, guilty.)

"You want me to hunt you down," the Winter Soldier repeats dubiously, still just those few careful inches away from Steve.

"You won't understand it yet," Steve says, the gut-deep tug behind his sternum letting him know that he is about to disappear for real. "But you're going to understand it soon. Find me, Bucky, please, I'm so—"

2014.

"—Sorry," Steve murmurs, and opens his eyes. Fighting the heavy pull of his eyelashes takes some effort, but he manages it after a brief struggle.

"On your left," someone says, and Steve blinks the blurry fog out of his eyes to meet Sam's warm gaze. "Morning, Cap."

"What..." Steve's too-thick tongue fails him, and he looks at Sam helplessly for an answer, but all Sam does is nod his head toward the foot of his bed. Steve turns his head to look where Sam directs him, and feels his heart nearly stutter to a stop in his chest.

"He dragged you out of the Potomac," Sam says, and there is something in his voice that Steve has not heard before, but he is beginning to think that he likes it. "Nurses had to threaten physical violence to let 'em take you into surgery without him."

Steve frowns, back aching where Sif's metal device had dug into his spine. "Bucky—" he rasps, and reaches out. Bucky—The Winter Soldier—whoever he is, reaches out his metal hand to take Steve's, carefully holding his busted knuckles not to hurt the stitches. "You're here," he says, joy pulsing under his tongue. "But—the machine, I have to—where's Sif...?"

"Tall lady with the hair?" Sam asks. Steve can't tear his eyes away from Bucky, has to nod and hope Sam understands. "She visited earlier, took back her medieval torture device."

"It breaches alternate realities," Steve says, amused.

"It looked like it wanted to breach my thumbs, that's all I'm saying," Sam counters mildly. Bucky's lips twitch; Steve grins back helplessly, even though it makes his split lip ache. "Anyway, she went back to Asgard yesterday. Which, by the way, freaks me the fuck out, but it's okay. I met a goddess. No big deal."

Steve laughs out loud, especially when Sam rises to ruffle his hair with one palm. "Thanks, Sam," he says, and looks up at him with gratitude blooming behind his open eyes. For everything.

"Yeah, yeah, you owe me, it's fine. I'll think of something for you to do. Walk my dog, maybe," Sam suggests, eyes crinkling at the corners as he smiles, and pats Steve's shoulder. "Nat and I are handling press cleanup, so I've got some shit to do. You get the job done, Rogers, but I gotta say, you sure as hell don't do it quietly."

"Your mom doesn't do it quietly," Steve retorts, and Sam snorts.

"Yeah, you're feeling better," he mutters, rolling his eyes. "I'll come see you again before you get discharged." He holds out his hand to Bucky, which Bucky accepts and shakes with only a heartbeat's hesitation. Steve watches them share a nod with a smile that aches deep at the base of his spine. It worked, then. The misalignment is healed.

As soon as Sam closes the door behind him, Steve is pulling Bucky closer, letting Bucky slide his flesh and blood palm upward to cup his cheek. "Bucky," he says, softly, agonized.

"Steve," Bucky says, equally quiet, and strokes the pad of his thumb over the crest of Steve's cheekbone.

"So I—I found you, then," Steve clarifies, eyelashes wet, and smiles unsteadily.

Bucky nods. "Yes," he says. Then, a line forming between his brows— "How?" He exhales, frown deepening. "Why?"

Steve laughs weakly. "Oh, that's easy," he answers, and holds Bucky's metal hand a little tighter. "You're my mission."