Steve takes a breath, shaking out his arms as he steps up onto the platform. Time travel. Why not? After everything that's happened in the past 100 years, nothing seems impossible anymore. He eased a plane down into Arctic and woke up 70 years later in New York City; it was like that, just backwards. Almost. He glances over at Bruce, busy tinkering away on a machine Steve has zero hopes of even beginning to understand. He trusts them—trusts Bruce, really—for this to work, but he can't help but feel like his stomach is going to turn inside out. It seemed like every time he thinks he has a grip on reality, it dissolves between his finger—-the Tesseract, S.H.I.E.L.D. tech, life on other planets, and now time travel. But if it works, they have a chance of saving billions of people. If it doesn't and Steve ends up stuck in the past or ends up scrambled eggs in the quantum realm, at least he would leave knowing he tried everything. No matter how small the chance that this would work, the chance to bring them all back was worth losing everything. Wakanda was without their king, Rocket had lost his entire family, and Steve had lost Bucky—

Bucky.

The pain twists his chest like a hot knife before he can stop it, letting out a small huff of surprise at how violently the pain still comes. Five years have passed, but the guilt and pain have barely lessened; Steve still bolts out of bed, shaking and covered in cold sweat at the the merciless nightmare that plagues him night after night. Bucky, eyes full of fear and confusion, saying his name one last time before dissolving into dust before him. He looks just as panicked as he did when he fell from that train in 1945 and Steve feels every bit as responsible as he did 80 years ago. He couldn't save him, couldn't do anything but grasp at what was left of him in the leaves. It should have been Steve. There was no logic to who disappeared and who stayed, only the itching surety that fate was hell-bent on tearing them apart again and again.

Something had broken off in his chest when Bucky disappeared, hollowing him out and leaving him gasping for breath. It was a different kind of pain than when Bucky plummeted to his death in Europe, something that felt less like consuming grief and more like someone had reached inside of his chest and pulled everything important, everything vital. It was the same twinge in his chest he had when Bucky broke his arm after falling off a bike when he was eleven, the thing that snapped Steve's eyes towards him when Bucky was injured on the battlefield even before he cried out. It was that bone-deep surety, taken and multiplied to an infinity that made Steve reconsider everything he knew about their relationship. The more the years wore on after the snap, the more he unraveled through his grief about what this meant. He missed them all, still mourned and grieved for the loss of Sam, for Wanda, for T'Challa. He missed Peggy, who would have known what to do; who would've kicked him off of his ass and told him to stop moping, to start fixing it. But there were times where he could recognize the world as it was, without them. It made him angry, made him despair, drove him to find some kind of solution to bring them back, but he realized that they were living in a very different world.

His mind would not accept that for Bucky. Logically, he knew that Bucky was gone; physically, he could feel whatever was binding them together had snapped and left him floating without a tether. But his mind came up against a barrier every time he thought about Bucky being gone, as if his heart and mind could not process the irreconcilable truth. He could not look out at the world and accept it, could not recognize it. The earth may continue turning for everyone else, but for him it had stopped five years ago. His heart, or whatever was left of it, screamed "bring him back bring him back bring him back he can't be gone not again" for the past five years.

He had saved him once from Hydra's experiments, seen him die, seen the blankness in his eyes when he called out to him, brought him back from Hydra's mind-control, protected him from virtually every country on earth and his own team, had watched him go back into cryofreeze, had asked for his help one last time and watched him dissolve into nothing but dust in front of him. Every time Bucky left, Steve grew closer and closer to realizing some buried truth within him. It had been just out of reach for the past century, but Steve had nothing but free time after the snap. There was chaos in the world, but so little that they could do, so little that he could do. No more existential fights, no more missions. Just him, Natasha, and an empty HQ. For the first time, he was able to search for that truth, finally wrapping his fingers around it and pulling until everything came into focus.

Tasha knew, of course. She had seen it from the second Steve realized the Winter Soldier was Bucky; she had watched him pull apart himself and the world to find Bucky again, to save him. She was constantly reminded of her own relationship with Clint, the way they fought death again and again for each other, the way they constantly hovered over the line of no return with each other, the decades of dancing around the subject and denying themselves the slightest consideration. She had watched Steve unravel over the past five years like she had never seen before, something teetering on hopelessness. She knew that he would volunteer to be the first to test Tony's new toys, knew where he would try to go and who he would try to find. She had turned away at the barely-concealed desperation in his eyes, left New York to track down Clint and bring him back from the edge. They were both tired of losing their second halves.

"You ready?" Bruce calls without looking up from the endless rows of dials and levers.

"As ready as I'll ever be." Steve flips his helmet on, glancing out at his teammates. This will work. It has to. For him, for Bucky, for all of them.

"You only have about a half an hour before I pull you out. Do whatever you have to to confirm the date, but do it fast." Another nod from Steve. Bruce grabbed a handle on the board and glanced back at Steve one more time. "Austria, November 3, 1943."

"Whatever it takes." He barely finishes before Bruce pulls the lever, shrinking him and rocketing him through time itself.

Steve pitches into the grass as he landed, sticks and rocks digging into his back as he struggled to breathe from the transition. Whatever Banner did, he had gotten him somewhere nowhere near mid-May New York; the landscape was too quiet, too forested, too much of a chill in the air. He tried to keep his focus solely on the mission, but he couldn't help but feel a flicker of hope—it could've worked. It was only the first step in the long list of highly temperamental variables, but this would be the closest they had gotten in five years.

Bruce had all but dropped him off at the front door of the Hydra weapons facility—no plane jump this time around. The building still looms in the forest, which was a good sign that he hadn't overshot his time frame, but they couldn't take chances that particle physics travel was imperfect in its timing. If he was going to bring over three billion people back to Earth, they couldn't be working on a margin of error larger than a day.

Though his 1943 memories aren't crystal clear, he navigates the building without getting alerting the guards, sticking to the shadows and ignoring the thrum of Tesseract-powered weaponry around him. He knows they'll all be destroyed by the night if he's gotten the date right, but he still wishes Howard had left the damn thing in the ocean. He wastes too many minutes waiting for the guards to change their rotation by the cells, but he's soon swinging himself up onto the catwalks above the makeshift prison. He chances a glance down one of the circular grates and his heart gives a painful twist at the sight of his old teammates as they grumble and argue among themselves. It would be so easy to snap the locks open and set them free to wreak havoc on the facility and start the long trek back to Italy. But he had gotten enough pointed remarks from both Bruce and Tony to not mess with anything to know that he shouldn't. They still didn't know exactly how time travel worked and no one was ready to risk the future being even more irreparably fucked up all because Steve didn't know how to stop. But if he set them free now, they would chalk up the Allied liberation to a stroke of good fortune and a hallucination, not Captain America. But if Steve never had a chance to save them, he would have been stuck as a propaganda tool in tights and would have never had clearance to put together the Howling Commandos, let alone go out into battle. But if he never got the Howling Commandos together, they would have never been on that train, and Bucky would've never—

He braces himself against the metal floor, pushing himself back from the gate. For the first time, he is realizing that he shouldn't have been the one to go. He feels his loyalties being pulled in two directions, painful and insistent. He could potentially save Bucky right now. He could save him from decades of brainwashing, of torture, of having his autonomy stripped away from him. Bucky had become someone far different from who he was in 1945, and Steve had a chance to fix that. Bucky could have a life, settle down after the war, have a chance at a normal life free from assassinating presidents and a metal arm. Maybe if he did this, the events of history would play out completely differently; Thanos would never get the chance to get all of the Infinity Stones. Tony would still have his parents...

How was he supposed to choose between that and leaving Bucky here, strapped to a table and made to be a Nazi science experiment? How was he supposed to leave the past knowing everything that comes in the future? Even if they manage to get all of the Infinity Stones and undo the snap, how is Steve supposed to ever look Bucky in the eyes knowing that he didn't save him? He punches the floor beneath him, sharp and quick, tired of constantly being pulled between his head and his heart. The soldiers beneath him give a yelp of surprise, crowding around the grate and demanding to know what's going on up there. Steve curses under his breath and runs to the end of the catwalks, jumping down and slipping into the hallway.

He never slips during missions.

Never used to.

He checks his watch, cursing again at the realization that he only has about 2 minutes left until Bruce pulls him back to 80 years in the future. He takes off at a sprint, following the turns of the maze-like halls like he does in his nightmares, though in the night he rarely finds Bucky alive on the table like he is now, struggling weakly against his restraints as Steve runs in. Zola was nowhere to be found, and Steve checks the desk for the daily calendar he know will be there. November 3rd, 1943. Bruce did it. They did it. He has few seconds to recognize their accomplishment before he sees Bucky's head lolling to the side on the table, muttering nonsense to himself. His pupils are blown and unfocused as he tries to make sense of who's running towards him, his drugged face twisting into what could be a smile. "Steve?"

Steve's hand reaches out towards Bucky's face, his chest tight and breathing short like he had just run 30 miles. "Buck, I-"

There's a blinding flash and he's back on the platform, his hand outstretched in front of him to cup a ghost's cheek. He drops it, blinking away the abrupt transition and letting the wave of emotions hit him again and again like a tidal wave, unchecked. What was he going to say to Bucky? In his drugged and delusional state, he would be surprised if Bucky remembered it, or if it was just another hallucination lost to those horrific weeks.

"Steve? Steve! Did it work?" He could hear Bruce's insistent shouts to him as the world pieced itself back together. He pushed back his helmet with a click, trying to focus on his teammates. It was 2023, though he felt like whatever had been wrenched from chest was lying on that table in 1943.

"It worked." His voice comes out hoarse and strained and he clears his throat, tried again. "It worked." He stood up, schooling his face into determination. There was a beat of silence as everyone took in what this meant, what they would have to do in the coming days. They could do it. It would take a million factors going right at the exact same time, but they could do it.

"Great, glad to know I was right as usual." Tony broke the silence, clapping his hands together. "Meet in fifteen. We've got work to do."