A/N: Written for this prompt on the Avengers kink meme: What if, because of all the brain frying, Bucky has developed Capgras Syndrome?

And when he finally gets around to looking for Steve after hunting down all those people who were in charge of him during the whole Winter Soldier gig, he's utterly convinced that this Steve Rogers is not the same one he grew up with so he kidnaps him and tortures him for information about where the "real" Steve is.

If you are unfamiliar with Capgras syndrome/delusion, I discuss it more in the concluding author's note.

Warning: This story deals heavily with torture. It does not linger on gory depictions, but depictions of torturous acts are there. This includes beatings (specifically about the face), being cut (specifically about the face and throat) and denailing, or the forced removal of fingernails. Proceed at your own risk.

It's a word—Bucky—that brings visions of the snow and the falling.

It's words—I'm with you 'till the end of the line—that halt his blows.

It isn't until he pulls the body with the familiar words from the water that the Soldier truly sees the face. It is bruised and bloodied but beneath the marring, it is perfect. The curve of the lips, the lines of the jaw, the arch of the brow. An exact match of the man he almost remembers. But the words made an ache deep in the Soldier's chest and the face doesn't pain him at all.

A forgery, he thinks, a clever copy. But not a perfect facsimile. Beautiful yet hollow. The words had tricked him but now that he is looking, the deception is clear. It is a ploy he does not care to decipher; now that he has memories, the memories take precedence. He leaves the duplicate in search of the original.

The man in his memories is named Steven Rogers. The Soldier remembers calling him Steve. He remembers fighting at Steve's side, growing up alongside him, being something other than a Soldier. There was a life before HYDRA, one he thinks he would like to return to.

But to do that, he must find Steve.

There is a place called the Smithsonian which claims to have information about Captain America. But the face in their photographs sparks the same nothing as the imposter in the Potomac. There is another stranger in the pictures, labeled James "Bucky" Barnes by the captions. Bucky. Another word that brought feelings paired with a face he doesn't know.

This is a trap, the Soldier decides, but those who set it are incompetent. He absorbs the information and leaves before they even attempt to kill or subdue him. Someone wants the world—and the Soldier specifically—to believe this double is the real Steve Rogers. Wants the Soldier to believe he is James "Bucky" Barnes. And then what, fight along the imitation's side? Lower his guard and be slaughtered?

He doesn't know the end game. But the thing wearing Steve's face, it will know.

The Soldier lets the thing "find" him. He has been aware of the man's pursuit for weeks but the False Steve seems to expect resistance on his part, so to give in too readily would be conspicuous. He lingers too long in a public space, pretends to be unaware of the man approaching from behind.

"Bucky?"

It is Steve's voice, hopeful and cautious and familiar. The Soldier drops all pretense of disregard, whirling around, eyes wide and searching.

There is only the fraud, wearing just the look that would have graced Steve's face. He steps back, raising his hands as though the Soldier is a wild thing he does not want to startle. "Bucky, it's me," he says, as if the lie isn't plain. "It's Steve. Do you remember?"

"I remember." He remembers that the sight of Steve would warm him down to the bones. Now, like always, he is cold.

The False Steve smiles. It is beautiful and empty. The Soldier allows the thing to lead him and once they are away from onlookers, he strikes the man unconscious.

By the time the thing awakes, he is bound to a chair. There are no windows in the room the Soldier has chosen for this interrogation; a lack of natural light disorients the body's internal clock and adds to unease.

"Bucky?" asks the creature in Steve's skin. Perfect hurt, perfect worry. Every detail flawless, save for the way the Soldier's heart is not moved. He doesn't understand why he should feel in his heart—it is only an organ; it lacks any connection to the amygdala save for the blood it pumps there—but when he thinks of Steve, that is where the sensations occur.

"You will tell me," says the Soldier, "what you have done with Steve Rogers."

The man's brow furrows just as Steve's would. "Bucky." His voice is slow, searching. He is trying very hard to be Steve. "Bucky, it's me. It's Steve. Come on, you remember me."

His arm slams across the thing's face. It would shatter an ordinary person's skull. The False Steve is not an ordinary person, and perhaps not even human. The Soldier might dissect the body once he has the necessary information; there may be clues inside as to its origin and purpose. "You will tell me," he repeats, "what you have done with Steve Rogers."

"Bucky, wait." His face is already blackening at the point of impact, but his eyes are not clouded with pain or disorientation. They stay clear, focused on the Soldier. "You're not thinking straight. You knew me on the helicarriers, I know you did. Whatever HYDRA did to you, you knew me. You still do. Think, Bucky."

He strikes the False Steve again in exactly the same place. This time the man cringes. "I will continue to beat you until you surrender the location of Steve Rogers. If blunt trauma does not persuade you, I will switch to blades. Then firearms." There are flecks of blood on his arm from the thing's mouth. He does not bother to wipe them away. "You will tell me what you have done with Steve Rogers."

"Bucky." The fraud's eyes are pleading and concerned and perfect. The Soldier feels nothing gazing into them. "It's Steve. I'm with you 'till the end of the line, can't you remember?"

The words give him pause. But that's all they are, words, and words can be parroted by anyone. He shakes his head, lashes out a third time. A lifetime ago, HYDRA sent blond scientists and officers to deal with him. He was not yet the Soldier, not anything, really, but his mind had latched onto what it could nearly recognize and he had behaved. He was manipulated for seventy years; the Soldier will not allow familiar faces and phrases to fool him any longer.

After twelve hours of beatings, the Soldier decides to switch to his knives.

Over the course of the day, the False Steve has tried many tactics. He has begged the Soldier to recognize him. He has made appeals to logic, listing all the ways he can prove his identity if the Soldier lets him go. He has made appeals to emotion, speaking of their friendship, flinching from pain, and sometimes, quickly and quietly, whimpering. He claims that the Soldier is sick and needs help.

"I am not malfunctioning," the Soldier says. There is blood everywhere. The thing heals rapidly but such interrogation is taxing on the body and if the False Steve does not drink soon, he may die or cease to be coherent. "I am not stupid, either. When I return to this room I shall begin cutting you, and if you continue to resist you will lose appendages."

He turns to retrieve a glass of water, ignoring the things the imposter is saying. The Soldier considers methods to make the act of hydration unpleasant but they all run the risk of inducing vomiting, which would defeat the purpose of giving the thing water to begin with. And providing necessities without pain may aid in camaraderie and make the False Steve more likely to volunteer information.

It isn't until he is filling the glass that he listens to any of the words from the other room.

"—just do what you feel you have to, Buck. It's all right, I can do this all day—"

The glass shatters in his metal hand, showering him in water and shards. The Soldier does not perceive it. That is Steve's voice, his Steve, not the thing wearing Steve's face. The ache returns to his chest and he leaves the water running as he rushes back into the room, eyes wide and searching.

There is only the man masquerading as his friend, fixing him with just the same worried stare that Steve would use. "Bucky?"

The Soldier does not waste the time and effort to growl in frustration. He draws a knife, lays the blade against the False Steve's throat. "Where is he."

Just from the way the thing opens his mouth, the Soldier knows he is going to spew the same lies from before. He presses down and beads of blood well up along the knife's edge. "I heard him, he was here. What have you done with him?"

The False Steve's eyes are bruised and half-shut, but the Soldier can see thoughts and calculation racing behind them. "That was me, Bucky. You recognized my voice."

"Liar!"

"Just close your eyes," the thing pleads. "Something's mixed up in your head, just close your eyes—"

The Soldier nearly rams the knife into the False Steve's eye. Instead he slices down the man's face from forehead to chin. Then another cut, horizontally. And another, and another, until the face before him no longer resembles Steve.

"It's all right," the False Steve says. He says it when the Soldier's knife is at his face. When the Soldier's knife is at his throat. His hands. His nails. Again and again, and the Soldier would tear out the thing's tongue if that wouldn't prevent him from conveying the real Steve's location. The False Steve's eyes are wet and compassionate, and the Soldier considers gouging them out.

"It's all right, Buck. I know you'd never hurt me on purpose." His body is tense from the attention of the Soldier's blade, shuddering. His voice is tight.

"You will tell me what you have done with Steve Rogers," the Soldier says.

"I'm not—" The words are cut off with a choked sob. "I'm not angry. You can't help it."

He speaks as Steve would. He responds to pain in much the same manner as the Soldier recalls a smaller, frailer body reacting. He is so very like Steve and it makes the Soldier's head ache and his heart pound. Where is Steve? How long has this thing had him, to emulate him so perfectly?

"You will tell me what you have done with Steve Rogers."

"I hope this makes you feel better, Bucky." The False Steve is grimacing and shivering, but he makes it sound sincere. "I hope—they hurt you so much. And I was never there. So this—it's really okay. I'm not mad. I'll never be mad at you."

It hurts the Soldier to cause him pain. It is like watching Steve come to harm. It is not Steve, it is a trick, but the Soldier's lungs feel constricted, breaths fast and shallow. Steve is trapped somewhere, possibly injured. Possibly dying. And the Soldier is empathizing with the thing that has taken his friend.

There is a wet snap as another of the thing's nails is pried away. There is a cry cut short. The Soldier thinks briefly, absurdly, that the thing is quiet for his benefit rather than to keep from showing weakness.

"You will tell me," the Soldier says, forcing his voice to be steady, "what you have done with Steve Rogers."

For some time the thing is quiet, panting. Trembling. Then: "Hey, Buck. Remember that time you and Teddy Evans got in a drinking contest? And you got sick all over your best shoes?"

The Soldier wipes his blade across the thing's pants. His hands are not shaking. They are not. He turns his attention to the next nail. "You will tell me."

"It's all right."

"Bucky."

The Soldier is waking, slipping slowly out of the fog between sleep and consciousness. He does not remember falling asleep. He cannot remember anything but carving and striking and worrying for Steve.

"Bucky."

Steve. The Soldier bolts upright, eyes open, mind racing to sort stimuli. Steve's voice. A blank expanse of wall before him. The thing tied to the chair must be behind him and what a fool he was to put his back to an enemy, even a bound one, but that is Steve's voice and Steve is here and together they can kill the thing wearing Steve's face—

"Wait." His voice is smooth and authoritative as the Soldier's best handlers and even if the Soldier were not trained to obey, this is Steve. The Soldier freezes, not even turning his head. "Close your eyes, Buck. Don't open them until I tell you to, no matter what."

A flicker of hesitation in his stomach. The thing with Steve's face must still be in this room. But now Steve is here too, and Steve will not mislead him. He closes his eyes, nodding.

"Are they shut?"

"Yes."

"Good. Good, Bucky. Now listen: I'm tied up. Do you think you can untie me without opening your eyes?"

The Soldier can make and loose knots in total darkness. That ability does not concern him. What does concern him is that the thing has managed to subdue and bind Steve. "Where is it?"

"What?"

"The thing that looks like you." His hands clench and he hears the metal whirring. "That tried to trick me into thinking it was you. Where is it?"

"Gone," Steve says quickly. "He—it's gone, don't worry. Just keep your eyes closed and get me outta this and I'll take care of it, okay? We're fine, Bucky. Everything's fine."

Everything is not fine because the scent of blood lingers like pennies and gasoline in the air. Because Steve is tied down and when the Soldier tugs at the ropes looping around the arms of the chair, he can hear the sharp intakes of breath that indicate injury.

But then Steve is loose and Steve is holding onto him—gingerly, but the Soldier knows the touch—and maybe things will become fine. Steve remains at his back—"You're doing good, Bucky, you're doing so good, keep your eyes shut for me"—and the Soldier hears him dial a cell phone and speak to someone on the other end of the line.

Time passes. Others arrive. There are hushed voices and quiet curses and the Soldier is led, still blind, into a vehicle. He does not struggle: Steve is here and as long as he can hold onto Steve and be assured of his presence, he does not need to see. For the first time in nearly a century Steve's hand—bloodied and shaking—grasps his own and the Soldier will never let go.

Steve's friends make the Soldier let go once they reach the hospital, saying Steve needs to see a doctor. Steve tells the Soldier not to open his eyes until Steve has left the room, so he does not.

Steve's friends are very nice to him. They make him lie down with machinery around his head, but it does not hurt like a memory wipe. It does not even touch him, only makes a lot of noise. They say it takes images of his brain.

They say his brain is damaged from decades of electricity. They say the part of his brain that recognizes faces doesn't always communicate properly with the part that creates feelings, so sometimes he can look at a person he knows without feeling like he knows them.

The Soldier doesn't really understand that. But he nods and listens to their ideas to help and asks politely if he can talk to Steve. And they always dial the phone and let him speak. Steve says he is all right. He says there is no scarring and he is not angry. The Soldier is very angry on his behalf and he thinks a lot about ways to kill the thing that looks like Steve. But he never says so now, because he did once and Steve became so quiet the Soldier thought he had hung up.

Sometimes he is given injections that make him drowsy and still and they tell him he can see Steve. But he never does. It's always the fake and no matter how many times he points out the difference, they never bring the right one. The False Steve is soft and smiling and holds his hand just right, and the Soldier thinks that maybe he does not hate the man, but it is hardly the same.

After, he will call the real Steve and tell him the thing that looks like him came back. Steve sighs into the phone each time: "Bucky, that was me." And the Soldier laughs because he remembers how to laugh now, because he is allowed to laugh, and because it wasn't Steve at all.

He dreams some nights that the False Steve comes to visit him. In the dreams he lies huddled under the blankets, frightened, until the False Steve touches his shoulder and whispers at him to close his eyes. Then he does, and Steve is back, and everything is all right.

A/N: Capgras delusion is a syndrome in which the afflicted believes that someone (or multiple people) close to them have been replaced by an identical double. There is debate as to the cause of Capgras delusion, whether it is a mental illness or a sign of brain damage, but one proposed theory is the one used in this fic: a disconnect between the part of the brain that recognizes faces and the part that feels emotions associated with people we know.

This disorder can also occur with photographs, as noted by neuroscientist Vilayanur Subramanian Ramachandran of the University of California. Ramachandran also observed a patient who was able to recognize his mother's voice when speaking to her on the phone, but viewed her as an imposter when seeing her in person.

Little is known in regards to the treatment of Capgras delusion. In cases of physical trauma, sometimes the brain can overcome the syndrome, and some patients are helped by medication. But for many, there is currently no cure and no way to convince the afflicted that their feelings are not reality.