Bucky follows the sounds of commotion through two labs, a guard station with two more incapacitated men, and some kind of canteen. The next room has been torn to pieces. Before someone took a sledgehammer to it, it could have been a doctor’s office. Medical equipment is scattered everywhere, but so are tools that look like they’d be more comfortable in Stark’s workshop. The scary part is the man-sized hole in one wall that leads to another lab in a state worse than the first. Or maybe it’s just more horrifying as there’s copious amounts of blood splattering the floor and walls.

[...]

Dressed in what looks like a alternatively-colored Captain America costume, a blank plate where his face should be, the guy looks a bit like the Iron Man suit. If the Iron Man suit didn’t have eyes and had been painted like a green and white American flag. Bucky’s eyes skim over all this and land on Steve’s shield. Now that Mr. Green’s turned around, Bucky can see more blood smearing the red, white, and blue surface. It’s Steve’s. Bucky doesn’t know how he knows, but he’s sure of that.

[...]

Mr. Green walks towards him slowly. Glancing behind him to find an empty hallway, Bucky steps backwards. If he can get Mr. Green away from the door, he knows Natasha can get Steve out.

[...]

Backing up further, he watches Mr. Green follow. Over the thing’s shoulder, he can see Natasha’s face in a small window, blood smeared across her jaw, eyes wild. Yet when she sees Bucky, her face breaks into a smile just before she disappears again.

[...]

Behind them, Bucky hears the battered metal door screech as it’s hauled aside. The sound echos through the underground lair. Bucky winces, but Adaptoid doesn’t even turn. A green hand, seemingly clad in a glove a lot like Steve’s, reaches up and pulls off Bucky’s mask. Everything in Bucky screams not to let him, to beat the weird green son-of-a-bitch to a pulp for what he’d done to Steve. Yet, behind the creature he can see Natasha supporting a pale, bloody Steve who can barely stay on his feet, so he swallows the reaction. Somehow, holds still.

[...]

“Time to go,” he says, catching Steve under the knees and around the back, lifting him bodily so they can run the rest of the way to the elevator. Natasha is limping, but she keeps up and drags the corpse Bucky had used to keep the elevator waiting for them out of the way.

Apparently alive enough to be appalled, Steve starts a lecture with, “Bucky,” and he has to cut him off.

[...]

“Why aren’t you healing?” Bucky demands as he pulls Steve out onto the grass towards the emergency evac location.

Steve, being Steve, doesn’t give a straight answer.

“He got me pretty good, Buck.”

“Nat?” Bucky demands. “Tell me.”

“It was strapped to a bed in one of the labs. We thought, you know, it would want our help, but it just went nuts. Attacked. Threw Steve through a wall.”

“Nat,” Steve says, trying to stop her which means it’s really, really bad.

“He picked up this metal, thing, I don’t know what it was-”

“F-clamp,” Steve says. He sounds resigned and far too tired.

“- and he just- It didn’t look like it could even be used like that, but he hit Steve. Hard.” Natasha’s voice skips and Bucky doesn’t think he’s seen her like this before, “And it went right into him and then that- that thing just ripped it out again.”

The cold of being frozen has nothing on the chill Bucky feels now. Natasha is right. You can’t stab someone with an F-clamp. You just...you can’t.