A/N: sorry again for the delay, on the other hand here's a holiday gift for you! =)

Bucky's first awareness was of a radiating ache that seemed to reach every inch of him. His face twisted into a grimace. It was hard not to feel strangled by the bandages stretching across his chest for stability. Otherwise, the occasion was remarkably normal. Softer bed than he'd had in years, warm blankets, sunlight beaming in through a window. A quiet room.

Well, almost, on the last one. Someone shuffled nearby—a jacket, a newspaper, he couldn't quite tell. Attempting to stay quiet, only to end up being the loudest thing in the room by comparison, given their surroundings.

Bucky tried to swallow, his throat uncomfortably dry, and opened his eyes. Howard Stark watched him from a chair against the opposite wall, his face difficult to read.

"Have you been there the whole time? I mean, it's touching, but kind of unsettling too—"

"Barnes…" The longer it took Stark to find words, the clearer it became that his strange expression had a reason behind it. Bucky's stomach dropped.

"What happened to the mission?"

"They found the base, blew things up, caused general mayhem. I still don't know a lot of details, they're en route back by now."

"Who'd we lose…?" croaked Bucky. The whole unit worked closely together, losing anyone would be a huge blow. Yet somehow he knew the news wouldn't be quite so tough to relay unless it was…

"Rogers, he's…he's missing. Schmidt launched some kind of super bomber, they couldn't stop it from taking off, so he jumped on instead. Took it down somewhere in the north Atlantic before it could reach the East Coast and kill a lot of people. We didn't get word until you were in surgery. I'm sorry…"

Time stopped. Everything in Bucky's perception stopped, except for a weird hum, almost a sense rather than a distinct sound. Very slowly, keenly aware of how his left shoulder didn't really touch the mattress, he rolled over to a sitting position. Cooler air swept around his mostly bare torso. Stark's half-hearted protests might as well have been behind glass. Bucky could tell his balance was off, though he stood anyway. He was in a small private room this time instead of a ward. Much shorter distance to the window. There he gripped the ledge for dear life, staring out over a sunny courtyard, the teeming city beyond.

Gone. Steve couldn't be gone. This wasn't supposed to happen. Screw war, screw duty and heroism and super serums. He didn't make it through all that hell just to lose Steve like this. Dammit, punk! And yet it was just like him to give himself up when there might be no other way, when so many lives were imminently at stake.

Stark didn't leave, but he let Bucky have his space, aside from one brief moment when he set a chair close to the window in case it was needed. Bucky ended up spending large portions of the next few days in that chair, bundled up in a robe so the nurses wouldn't have to wrestle a shirt to get to his bandages. His surgery had gone well. Based on preliminary ideas for the prosthetic, the surgeon had gone ahead and done the amputation at the shoulder joint.

That chair was where the Commandos found him when they finally arrived in London the fourth day after the news broke. He let them share updates, their condolences, favorite stories (it was their loss too, and not a small one), but didn't say much himself. They didn't press him on the matter. Then came V-E Day. Amid the somewhat buoyed mood, someone mentioned speculations of a special memorial to Captain America's legacy in the war effort.

"As a way to lay him to rest even though they haven't found him?" Bucky finally spoke up, curious.

"You can't exactly downplay the impact he had across the country. Across all the Allies, really," reasoned Gabe. "Whether with the USO shows, the newsreel films, the comics they started printing. Gotta admit, it's impressive what he did in just a couple years."

"Any talk of when they might be presenting this thing?"

"Not so far…why?"

Bucky scrambled to his feet so fast the others startled. "Where's Stark? I need to ask him a couple questions…"

. . .

"You think that'll be a strong enough attachment?" asked Bucky. His view of the schematic was off-kilter despite his attempt to tilt his head from where he lay. Unfortunately he was limited until the orderly could finish cleaning and redressing his shoulder. This one preferred a flat, unimpeded view of her work area. She wasn't the most gentle or nuanced about it, either.

"On top of what I'm sure is increased natural integrity—from, you know—we'll have this base that fits around the bone itself, and which the rest of the arm will anchor to, like a complete replacement joint that can't be pulled out of place," Stark reassured him. "I don't know how…you know, he figured so much of this stuff, but it seems to check out."

Bucky tried not to flinch at the veiled reference. Or maybe it was just the rather forceful prod to his shoulder that got to him. At least Stark tried to avoid Zola by name when they talked. Most nights Bucky still had nightmares about the demented scientist; he tended to react involuntarily at the very mention of his former tormentor.

"Anyway, I think I've got an effective working model of the understructure made out of scrap metals, now we're just waiting on the real material to arrive."

"You mean you actually found someone that can get it?"

"Who has it, how about we stick to that part. It's not easy to move the stuff and keep it low profile. If you ask me, the fella's a little sparse upstairs to begin with, but get a drink or two in 'im, and some of those stories make you wonder what he's been through out there."

"Well, that leaves me brimming with confidence."

"The best part in my opinion is how I solved the matter of powering the whole thing. Several of the designs work off of this…cube, it comes up all over the place. It occurred to me that I still have that glowing cartridge the Captain brought back from the first HYDRA base. Never seen anything like it. I'd bet you a dozen of Phillips' favorite steaks it's related somehow to the cube. And if that's the case, based on what I've read, we might just be in luck."

"It's not going to spontaneously vaporize me, is it?"

"Oh no, the power cell itself is incredibly stable, for how much energy it gives off. Self-sustaining, as far as I can tell. No detectable byproducts or emissions to worry about. I even figured out how to hook it into to the prosthetic, so it fits inside the arm itself. We'll just have to leave this section open until the end. That way we don't have to worry about it doing anything unexpected while I'm putting everything together."

The orderly tapped Bucky between the shoulder blades. "Sit up carefully, so I can secure this." She held fresh gauze to his left shoulder. Bucky did as instructed. Once she was done manhandling him into the dressing, he slipped his robe back on and faced Stark properly. The orderly gathered everything to be discarded with a huff, until Bucky could practically feel her passive-aggression boring into him.

"Yes, thank you, until next time," he finally relented, matching her demeanor.

"Well, you could stand to be better mannered toward those caring for you," she snipped in return.

"Maybe if you went about that care as if I were a conscious man and not a ragdoll. You could at least ask whether I'm still doing okay once in a while."

She stormed out. Stark raised his eyebrows, though he made sure she couldn't catch him doing so. "That escalated quickly."

"You're in here often enough to see how most of them do it. I think a roller coaster would have less jostling and more conversation than when she's on duty. Can we just get back to the plan?"

"Suit yourself. So like I was saying, we'll only have to deal with the core of the arm in the OR. The rest can be assembled after you're out and awake."

"And this should work pretty much like a real arm?"

"For all intents and purposes. It'll be stiffer at the joints than a real arm, but we can't really get around that without compromising stability. If you want a more detailed explanation of anatomy, ask the docs. They've already gone over it about five times for me to get this far, and some of it's still over my head."

A knock at the door snagged their attention, especially when they realized it was Agent Carter. Both of them straightened up where they sat, a significant contrast to their regard for grumpy hospital staff. She nodded to them. "Good afternoon, gentlemen."

"Hey, thanks for being able to swing by. So listen, Stark, that's looking great. I think we've just about got it nailed down. Let me know when everything comes in to actually build it, we can make the final tweaks then. Sound good?" Bucky hurriedly changed tact. This redoubled Stark's flustered agitation, a little blindsided by the hint.

"Yeah, uh, I can get right on that." He scooped up his pile of sketches and research, and headed for the door. "Agent Carter."

"Mr. Stark," she replied. After his exit, she turned to Bucky with a questioning expression.

"I didn't mean for it to be that abrupt, okay?" blustered Bucky.

"Clearly this elaborate scheme between the two of you is coming together, or at least it seems to be. What did you want to speak about so urgently that couldn't be said over the telephone?"

"Well, the big question'll be if the plan works, but it also relates to what I wanted to ask. I know the bigwigs have been talking to you about…organizing the memorial thing. He…Steve's basically the reason I'm still here, not to mention he was the first to push for the mechanical arm idea. And the boys were talking the other day about how much he, well, Captain America did as a symbol, not just a soldier."

The atmosphere in the room became much more somber. Agent Carter was very good at holding the depth of her emotions in check. Bucky remembered that night in the pub, how she only had eyes for Steve. Already it felt like a lifetime ago.

"What if we could continue what he started? If I continued it, to be specific. I would keep working with the SSR, as I assume you were going to ask Steve, doing whatever you might need a super soldier to take care of. It won't replace him, of course, but the world would still have Captain America. Maybe, if you're okay with it, and we pull this off in time, it could be part of the whole unveiling. And maybe one day I'll feel like I've finally repaid him."

"I don't exactly have the final word on either of those points, but I think it's a truly admirable suggestion. There is talk of forming a more permanent section, in light of what we've learned by tracking down Schmidt's base. Some people have concerns that the Soviets may have an interest in any HYDRA remnants they can get their hands on. I will see what I can do…Steve always spoke of you as a brother. I'm sorry for your loss," Agent Carter said quietly.

"I would say the same about him in a heartbeat. Best friend I could ever have. For what it's worth, I'm sorry too…"

The barest cracks surfaced in her composure. Bucky extended his one arm to offer her some comfort. For both of them, really. She allowed him to embrace her. In any other moment, he might have tried to steer the encounter toward romance. However, knowing that there had been sparks between her and Steve, any sort of proposition just felt wrong. No, this was one round that his best friend deserved to win.

The pieces fell into place more quickly than expected, especially on Stark's end. Once he had the vibranium, crafting the prosthetic was a blur. Bucky almost didn't have time to get nervous about heading to the operating table again. Almost.

They went with a heavier approach to the anesthetic this time. Bucky still didn't remember anything clearly from the last one, and it wasn't as if he had been able to move at the time, but the hazy vision of blood, the grating sound and feel of a saw was more than he ever needed to know. The new formula at least blocked any sense of what was going on around him, though he hovered on some level of awareness that he was in a room, on a solid surface.

He fully awoke back in his familiar hospital bed. More bandages padded his left shoulder, which felt strangely thick after having just gotten used to the balance of only one arm. The bizarre part was finally getting the guts to actually look, and seeing the thin frame of a limb, almost like a shiny version of his bones regrown, nothing else.

Bucky couldn't move any of it yet. It was probably best that he didn't, anyway, until his shoulder had a chance to recover again. Stark had to attach a few external pieces before this progressed too far, with the help of morphine injections. The bulk of the assembly came once the doctor was sure infection would not be a factor.

"I'm glad we figured out that flexible sleeve to fine tune most of the plates, so we could see how they moved together for the most part. This is fitting a lot faster than I thought it would," Stark commented, half to himself.

"How long do you think it'll take to get it powered up and try it out?" asked Bucky. Interesting as it was to watch the pieces gradually begin to resemble an arm, the anticipation was really getting to him.

"I just want to make sure I've secured everything that I can first. The last thing either of us needs is flying metal, or to get my fingers caught while trying to finish the job, if it moves unexpectedly."

"But I should be able to just hold it still, right?"

"We can talk through it all we want, we're not going to know for sure until we actually plug it in. And considering I very carefully took the power cartridge out of its casing in order to save space, who knows what'll happen if it touches the wrong surface."

"I might just get fried in the process?"

"Hey, have I done anything for you guys that hasn't worked out as planned?"

Bucky fixed him with a dubious look. "I did see your demonstration in New York a few years ago. The almost-flying car."

Stark froze, his mouth hanging slightly open. Then he ducked into adjusting some tiny cog once more.

At last he pronounced the work as complete as he was going to get in this stage, and pulled out an insulated box, very small tongs, welding gloves, and a pair of goggles. Both of them held their breath. Bucky had to look away when Stark retrieved the mysterious glowing whatever-it-was, the light was so intense.

Without warning, his whole left side felt like a lightning strike. He couldn't help jumping bolt upright in shock, nor the shout that accompanied the reflex. A dozen points of fire seemed to burrow into his shoulder while sheer power wound up and down a limb of which he was now very much aware. He had no idea what was happening, his eyes were clamped shut. His lungs refused to work. He couldn't move anything else, as far as he could tell.

And just as suddenly it all stopped. His shoulder throbbed. His heart pounded in his throat. He realized his chest was now working overtime, breathing so hard that it hurt. He could feel the soft sheets and mattress still under him.

Stark clambered up from where he had landed at the foot of the wall. His jaw went completely slack. Bucky looked down. The steaming metal arm that turned palm-up toward him was not what it had appeared to be less than a minute ago. The shape was much smoother, contoured exactly like a real human one, and the way it moved…if that wasn't astounding enough, the gap in his mid-upper arm revealed vastly more complex inner workings. The whole thing had a hum to it, too.

"What—how—" he stuttered.

"The cube," gasped Stark. "All the notes written about the supposed power cube, the way it I guess jump-started these battery things…I chalked it up to what looked like an obsession with Norse myth, but what if there's really something to it? A power source literally on a different level of existence than us. It's not just running your arm, it enhanced it!"

Bucky put his right hand on his left shoulder, experimentally pivoted the joint. "It's like the inner parts are fused in. I don't feel any difference compared to how my other shoulder moves. I-I don't know how to describe it." He picked up Stark's dropped tongs in his metal hand. The handle crumpled under his fingers.

"Uh, you might be careful how you hold things, until you get the hang of how strong your grip is," Stark belatedly suggested.

"Sorry…that really is incredible…"

"And that's just secondary power. Imagine what the actual cube might be able to do." An odd look crossed Stark's face. "They never did find it when they stormed the last base."

"Schmidt himself piloted the super bomber, didn't he?" ventured Bucky.

"He would have needed a substantial power source. That was supposed to be his escape as well as his pièce de résistance. Now aside from the round-the-clock work I've been putting into this thing—which all feels woefully inadequate, by the way, after the unexpected transformation—I just finished an instrument for measuring the unique energy signature that currently runs your arm, which I bet matches the cube—"

"Which means you can find the bomber," Bucky concluded for him.

. . .

Bucky fidgeted in the brand new suit, flexing the stiff gloves, elbows, knees, trying to break in the joints so he wouldn't look like a storefront mannequin when it was his turn. How did Steve put up with the dog and pony routine for so long? Maybe this was a bad idea. What if the crowd thought the same thing that was running through his head—that he was just impersonating Captain America?

He shrugged uncomfortably in the replica shield harness. Having worn the real thing before, it didn't feel right, didn't sit with the same weight. The current shield was mainly for show, as the only vibranium version had gone down with Steve. Obtaining enough for his arm alone (which could possibly serve the same purpose, in a lot of ways) was a tall order. Bucky glanced down at his hands. Fresh leather hid the difference between the two. One ordinary, vulnerable flesh, the other powerful and gleaming metal. He knew it was best to keep that under wraps for now. Less shock to the spectators, and less details broadcast to the Soviets.

Senator Brand rambled on overdramatically about his personal history with Captain America. Of course the politician weaseled his way into hosting the whole affair. Bucky chuckled to himself; Steve would have hated being fussed over like this. At any rate, Bucky was less concerned with eulogies on the White House lawn, and more preoccupied with the arrival of Gabe, Falsworth, and Dernier in the hallway where he waited.

"Morita hear anything yet?"

"They're still running blind since the cube was located with no sign of the plane, but Stark's sure it's got to be somewhere around there," Gabe replied heavily.

Bucky swallowed hard. "This would be a tiny bit easier if we at least knew…"

A round of applause signaled that he had no time left to stall. A barrage of supportive thumps to his back prodded Bucky toward the door. Outside, Peggy's encouraging expression stood out from the faces waiting for him to appear. She nodded. Heart pounding, Bucky touched the star emblazoned on his chest.

'Til the end of the line, pal…

He stepped out into the sunlight.

A/N: Yes I know the Tesseract is the Space Stone, so I'm fudging with powers a bit. But I liked the nerdy bonding between Stark and Bucky, as well as the sense of barely scratching the surface of this still-mysterious power source with which they're experimenting (plus I wanted a relatively uncomplicated way of explaining how Bucky ends up with his badass arm in this scenario).