It happens in Siberia.

"No," Tony says, and it sounds like it's been punched out of him, breathless and agonized. His pained tone is just enough of a contrast to his vivid anger that Steve pauses.

Bucky does too, arms raised to defend himself, one still outstretched from a blow that made contact.

And then Tony is pointing toward the exit with a metal coated finger and rasping, "Get out."

And then Bucky is stumbling backwards, and then he's scrambling, and then he turns and sprints.

Steve glances once more at Tony, who looks crumpled into himself, the smallest he ever has, and then he darts after Bucky.

Tony puts a gauntleted hand to his chest, grasping at the place where he can feel the soulbond that just clicked into place, scrabbling with his fingers like he can get underneath his ribcage and tear it out.

He can still see the clip playing out in front of him, see his father's head being bludgeoned, see a hand around his mother's neck. The footage was grainy, but Tony sees it all play out in crystal clear visions.

That's his soulmate.

His parents didn't die in the crash.

Nothing was ever an accident. His mother didn't have to die.

"No," he says again, out loud, like that will help. Like he can refuse the bond settling in his chest, like if he says no enough times it will go away, and he can go back to being bondless. "No."

...

"What happened?" Steve asks.

Bucky blinks slowly, looks at him. He can feel the tug in his chest asking him to go back. He can remember the moment it snapped into place, the moment his fist collided with the side of Tony Stark's face.

There was a split second of confusion and wonder and then there was only pain, and Bucky has heard that rejected bonds can hurt but he didn't think it was physical, didn't think it could hurt inside of him like this.

"He's my soulmate," he tells Steve, his voice creaking like the wood of an old ship, and then he says nothing else.

…

The thing is, Bucky can never know if he remembers everything. He doesn't know what everything could possibly encompass, he cannot know the full scope of what he's done.

He remembers Howard, though. He remembers his wife, Maria.

He remembers them.

He's not sure if that makes it worse, or better.

…

Tony returns to the States and drinks until he can't feel the thrumming in his chest anymore.

Pepper finds him, because of course she does.

"Oh, Tony."

Tony looks up at her, bleary.

She doesn't try to say anything else, just helps him to bed.

He doesn't deserve her.

…

Steve hovers, because of course he does. He's always been a mother hen, even when he was half Bucky's height. And Bucky gets it, he has the same tendencies, but there's an ache in his chest and his brain is Swiss cheese and he's ninety fucking years old and he doesn't need protecting.

But snapping at Steve doesn't make him feel better; it only makes Steve do the stupid hangdog face and then Bucky has more to feel guilty for.

…

Tony knows he should probably talk to Pepper about what happened. About the throb in his chest pulling him toward a man he won't forgive.

But there's always been a big difference between knowing what he should do, what would be good for him in the long term, and actually doing it.

He doesn't tell her.

He does, however, make a sizable dent in his collection of fine scotches.

It's fine.

He's fine.

…

Steve has files.

Cabinets full of them, things they found when looking for Bucky. Files about him. About what he did.

Steve doesn't want Bucky to look at the files.

"It wasn't you! You don't need to… it's only going to hurt you."

"It's my life!" Bucky yells.

"Bucky, you don't have to… to torture yourself with this. It wasn't you."

"It was me, Steve. Maybe I didn't choose it, but it was still me, and I need to know."

It's Sam's voice that stops both of them in their tracks, quiet but with an undercurrent of pure steel.

"Steve," Sam says. "Would you really take this choice away from him?"

Steve deflates.

Bucky has never felt less like winning.

He takes the files anyway.

The body count piles up.

Some of them he remembers.

Some of them he doesn't, not even with a file in front of him.

The file on Howard and Maria Stark is thick, full of their lives and accomplishments, things HYDRA hated them for.

They talk about Tony, too. He's deemed irrelevant. Written off. Not important.

The file is damp in one place, a small round circle.

Then another.

It's him.

He's crying.

…

Maybe someday, Tony will be a better man. Maybe someday, he'll be able to look at Barnes without seeing a hand close around his mother's neck.

Maybe.

Someday.

But not now.

…