Prologue:

October. 2023. The Universe Next Door.

Tony was being electrocuted. The power flowed down his arm, through his veins, making his muscles seize. Every atom in his body was vibrating hard and fast and he was shaking apart on some molecular level, but he had a job, goddammit. He had to reverse all the fucked up shit that had happened in the last five years. He had to get the kid back—

Thanos hit him in the chest, and it was like being hit by a train, the engine and the cars and the little red caboose, all at once. Things broke. His ribs. His sternum. All the while, his muscles kept seizing from the shock. The pain was blinding white, so pure it was well-nigh divine. He was flat on his back, and he needed to get up. Get up! He rolled over, tried to gain his knees, but Thanos's foot came down on his elbow. A giant hand closed around his wrist and wrenched. Ligaments ripped. Bones parted. Skin tore. He screamed, somewhere between agony and ecstasy, collapsing back belly-down in the mud. Then the white light pain sped away, and the darkness started to collapse in on him, and–

"No," he whispered, then, a little stronger, through gritted teeth, "No."

He levered himself up on his remaining arm; he wasn't going to die bleeding out with his face in the fucking dirt. He was going down fighting, even if the only fight he had left was to crawl across the ground and—

Pepper streaked from the sky like a meteor, crashing full speed into Thanos's knee. It was smart, unexpected. Keep it weird, Pep, Tony thought, filled with pride. Thanos toppled like a block tower and hit the ground hard. Tony's sundered arm popped free of his grip and bounced along the ground. Tony could see the exposed end of his bone poking from the limb, so white and frankly bone-y, it looked cartoonish, like a prop from a cheap horror movie. It was so ludicrous Tony almost laughed when Pepper fell on top of it like a fumbled football. Immediately, the nanites of her suit swarmed over the infinity stones stuck to Tony's used-to-be-hand, pulling them into place across the knuckles of her own gauntlet, and power swarmed down her arm, lighting up her veins.

She opened her mouth; it was full of white light.

She raised her hand.

And snapped.

An animal wail came from Tony's throat, ripped out of him by something with teeth and claws, and he collapsed, howling, as half her body turned gray, like a column of ashes, and crumbled before his eyes.

⁂

Steve was running, the massive Chitauri war dog hot on his heels. Its breath stank of blood; it was so close, Steve could feel the reeking heat on the back of his neck. And it would catch him. He couldn't outrun it, and when its jaws closed around him, Steve would die. But Steve was unwilling to die.

There was a Wakandan spear on the ground, just ahead. Not even a spear, just a half, but the half left was the business end. When Steve reached it, he dropped to the ground, his fingers closing around the broken shaft. The war dog, moving too fast to stop, ran right over him, and Steve thrust up into its belly. The point pierced armor and skin, and he kept pushing, until the broken spear was lost in its guts.

The beast fell hard on top of him, crushing the air from his lungs. For a terrible moment, Steve wasn't sure he'd ever draw another breath; he would suffocate, trapped under the carcass. But after the initial panic, he could feel that his hand was free, and he wriggled, inch by inch, towards that promise of air until he poked his head out, gasping. He shoved at the beast, strained against its crushing weight, but he stayed pinned. Then came the scream. He'd have known it anywhere, and his head came up, scanning the field for Tony. Later, he wished he hadn't looked, wished he hadn't heard the cry, hadn't seen what came next, because there was nothing he could do until it was too late. But then, he was always, always, always too late when it came to Tony Stark.

Steve watched Thanos rip off Tony's arm and leave him mangled in the dirt. He watched Pepper tackle Thanos to the ground, watched her get the stones, watched her Snap, watched the war dog dissolve into ash on top of him. Then, at least, he didn't have to watch anymore. He started running, pelting across the ground faster than he'd ever run in his life. He reached Pepper first: hopeless. The right half of her body was ruined already, gray and crumbling, but her remaining eye turned towards him, her lips moving. He fell to his knees and put his ear to her whispering mouth.

"Steve," she sighed, "they're yours. I'm giving them to you."

"Okay," Steve assured her. "They're mine. I'll take care of them." For a moment, he thought she meant the stones, and then—

"Don't let him wait too long, Steve. You've waited long enough, and they're both yours."

He drew back, surprised, but when he looked to her face, she was gone. Carol appeared beside him, hovering an inch above the ground.

"Get the stones," he said without preamble, and then he was up again, pounding across the battlefield.

Tony had collapsed face first in the mud, shoulders heaving. He was wailing, inarticulate, but still alive. Alive. Steve grabbed that fact and held it close. Now he just had to keep him that way. He rolled Tony over, pulling at the tourniquet on his belt.

"I'm sorry, Tony," Steve murmured, tearing at the armor, exposing more of Tony's freely bleeding stump. "This will hurt. One, two—" He pulled the tourniquet strap tight as Tony screamed anew, for Steve this time, for the pain he was out, Steve him black out. It would be a Tony continued to scream.

Steve swept him up into his arms, carrying him from the battlefield like a bloody bride.