As soon as Steve hugs him, the way he holds onto him, his hand clutching hard at Bucky’s jacket, Bucky knows Steve isn’t coming back from this mission. Not really.
So, when Steve fails to appear on the pedestal, and then he sees the figure sitting on the bench, shoulders bowed with age but posture still straight in a way that Bucky recognizes in his bones, he knows it’s Steve.
He lets Sam approach first, lets Sam have his moment, glad when he sees Sam take up the shield. Sam deserves it. He's maybe the best of all of them, flying into danger without any special powers or super healing. And Sam is a friend. Maybe the person he's closest to, after Steve. He's also relieved that it'll be Sam carrying the shield, that glorified target. All he’s ever wanted was for Steve to be safe, and he's not naïve enough to think age will stop Steve from fighting. But if he’s given up the shield, he's given up the fight, and he’s as safe as he can be.
After they’ve talked, their voices low enough that Bucky can’t hear what they’re saying, Sam finally steps back and turns to Bucky. He gives him an encouraging nod, and only then does Bucky move toward the bench, his jaw clenched in anticipation, his hands clutched into tight fists in the pockets of his jacket.
He wonders if he’ll recognize this version of Steve, but of course he does. Steve runs through his blood, whether he’s a scrawny punk or a strapping hero or this quiet old man sitting on a bench.
Steve smiles at him, the expression tight at the corner of his eyes, as if he’s not sure of his welcome with Bucky.
Bucky takes his hands out of his pockets, opening the fists and resting them on his thighs as he sits down beside Steve. On his left, because that’s where Steve always needed him.
The two of them sit on the bench for the longest time, staring out at the shimmering surface of the lake in front of them, a pregnant silence building between them.
Steve is the one who speaks first.
“I saved him,” he says. “I couldn’t save you, but I saved him.”
Bucky knows immediately who he’s talking about, and he takes a sharp breath in.
He doesn’t remember a lot from his time with Hydra, but he's recovered fragments of the early days, when his shattered arm was a constant agony and he still harboured hope that Steve would rescue him. After a time, the hope was its own form of torture and he was almost relieved when they started clawing his memories from him.
“When?” he croaks, surprised that he can speak at all.
“Three weeks after you fell.” Steve stops and corrects himself. “After he fell. Peggy and Howard rounded up the Howlies, and we found the Hydra lab where they were keeping you... I mean him.”
“Did you tell them you were from the future?”
“Didn’t have to,” he says proudly. “Peggy figured it out. And Howard wasn’t far behind her.”
“And the Howlies believed you?”
“Of course, they did. Time travel wasn’t even the weirdest thing we saw during the war, was it?”
Steve's right about that. There'd been guys with skulls for heads and glowing sci-fi ray guns and Hydra flying machines right outta Buck Rogers.
"And that wasn't all they figured out," Steve continues. "Howard started reverse engineering Pym's tech right away. It took him a while. Tony finished the job when he was at MIT. Made it so you could skip to different timelines." Steve holds up his arm, and Bucky sees a bracelet wrapped around his wrist, flashier and smaller than the controller Steve used to go back in time in the first place, exactly the sort of thing Tony Stark would make. "It's how I got back here."
"MIT?" Bucky starts working things out. "When he was in college? That means you could have come back years ago." He feels a sharp pull of betrayal, that Steve chose to stay with Peggy and that other Bucky, rather than come back here to him while he was still young.
Steve grimaces, and takes a deep breathe.
"I'm sorry," he says, finally turning to meet Bucky's gaze. Bucky's always been able to read what's in those eyes: determination, anger, loyalty, sorrow. Love. Bucky looks into those eyes now, and he see all of that, but he doesn't see regret.
"No, you're not."
Steve slouches, ever so slightly, and when he speaks, his voice is gentle.
"I'm sorry I went without you. But, no, I'm not sorry I went back. I'm not sorry I rescued him. I'm not sorry I got more time with Peggy." He pauses and sits up straighter, his gaze going out to the lake, but Bucky can tell he's not seeing the flash of sun on water.
"We had a good life," Steve says. "All three of us. Together. Peggy ran SHIELD, he worked with Howard, and I held down the fort and planned in the background."
"What about Zola?" Bucky can't help but ask. "What about Pierce? What about Hydra?"
"Gone." Steve's expression is one of grim satisfaction. "I pointed her in the right direction, and Peggy pulled them out by the roots and salted the earth they came from."
"Good." Steve's not the only one satisfied by Hydra's demise. At least there's one timeline free of those bastards.
They sit quietly together, and it's…nice. There's no fight on the horizon, no bad guys in need of a beating, just two friends, more than friends, enjoying each other's company. But Bucky can't help but feel that their time together, as always, is borrowed.
"You going back there?" he finally asks.
He braces himself for the answer, but Steve shakes his head.
Steve leans forward, his arms wrapped around himself.
"I promised him, promised both of them, what I promised you," Steve says, still looking out at the water, his voice gone heavy with emotion. "I'm with you 'til the end of the line." Steve stops talking and Bucky can see his mouth quiver, can see unshed tears gather on his lashes. Steve hugs himself tighter and takes a great heaving breath before he confirms what Bucky already knows. "There's no one left for me there."
Bucky closes the last distance between them without thinking, relief that Steve is back for good warring with grief at what Steve has lost yet again.
"You've got me, here," Bucky says. He puts an arm around Steve and pulls him close. "'Til the end of the line."
They stay there, on the bench, watching the water until the sun goes down.