A/N: Written for the Secret Santa on Providence Playground for Purple-Cat-Princess. Why am I only posting it here now? I have no idea. Implied Van César, some disturbing imagery. Fixed a couple missing words here and there. Enjoy.
"Can't wake up in sweat 'cause it ain't over yet,
Still dancing with your demons, victim of your own creation."
From "Nightmare" by Avenged Sevenfold

"Just breathe deep and count backwards from ten," Doctor Holiday smiled down at him just like she did every time they had to have this conversation. Rex winced. He hated the gas, though he'd stopped whining about it every time they needed to use it. She ruffled his hair – the action had always felt familiar, even when she was still more or less a stranger to him – and he took deep, even breaths.

Ten, nine… he could feel his eyelids getting heavy even through his Nanites trying to counter the gas. Eight, seven… his Nanites kicked into overdrive in their effort to counter the gas. He hated that feeling and the feeling that came with fighting the urge to fight it, but she always pumped a second – much stronger – gas into his lungs as he continued to count. Six… he never made it past six, the second gas forcing him out. Knowing that the dreams would happen never stopped him from wishing they wouldn't.

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The dark-haired lab tech ruffled his hair with a smile, shooing him off to do homework or sleep or some other unimportant thing they both knew he wouldn't do. Rex giggled before he scampered off; he knew the man's secret, how he and César would get close in the labs when they weren't working on their silly robot project. They gave him candy so he wouldn't tell on them, but all three of them knew he wouldn't say anything – he liked the lab tech with the funny accent that ruffled his hair just like his brother did too much to risk he'd be reassigned. "Tell César I said hi!" he shouted at the lab tech before he ran out the door to go and find his parents. Maybe they would want to play with him.

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Rex sat at the table drinking apple juice while César and the lab tech talked in the hall. Every once in a while he caught words like "Nanites", "tests" and "sponsors" – things about their little project that he didn't really care about. He finished his juice and started nibbling on the cookie they'd given him, a happy smile on his face as he kicked his legs. And then he heard César say his name. "—Rex as a test subject."

"He's your brother," the lab tech protested in a hushed voice, "it could get him killed!"

César started to respond, but he glanced in the room, saw Rex watching him and shook his head at the lab tech. "We'll discuss this later, Jeremiah." He came and scooped Rex up with a smile, digging into one of the cabinets for the package to fetch the boy another cookie. "Don't tell papi I let you have extra."

"Okay!" Rex knew that not telling papi usually meant forget all about it when it came from César, so he promptly did exactly that while he started nibbling on the second cookie.

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It'd been more than two weeks since the strange discussion between his brother and the lab tech, and the mood between the two of them had gotten… tense. They even left the door open when they were digging through boxes in the storage lockers – Rex knew mama and papi had forbidden him from being in the storage lockers, so he intended to make the most of the open door to find out what was in there. Even if it was just a bunch of boring boxes like everyone said, he still had to see that for himself to know for sure. How did he know they weren't hiding all kinds of awesome toys in there after all?

He looked from the door first to see if he could see them; they were off in the corner with their backs to him, having what sounded like a heated argument over something in the box. With a devious smirk at their backs he slipped into the room, careful to be quiet so they didn't catch him before he had a chance to look in at least one of the boxes. The one closest to the door was open, so he tried to pull himself up enough to look into it. It ended up tipping over a bit and whatever was inside rattled, but they didn't seem to notice so he got a glance inside. Nothing interesting.

There were a bunch of boxes piled up near a great big one – big enough to hide something fun, he thought – and he started trying to pull himself up on the first box in the pile, using the big one as leverage to keep him from falling back over. It was heavy and didn't move, even when he put all his weight on it to see if he really had to climb all the way to the top to see what was in it, so he climbed up on the second box and reached up for the edge of the big one. He pulled himself up and, bracing his feet on the side of the box, peeked over the top to glance down in it. It was a robot thing!

Cool! Rex thought and managed to pull himself up higher so he could reach in, trying to touch it to see if it would move. As soon as he realized that it did, he wished he'd never set foot in the lab in the first place. The thing's eyes flashed red and it lunged for him, knocking the box over in the process with a loud metallic thunk. He hit the ground hard, stars exploding before his eyes and a loud ringing filling his ears, blinking away the blur of tears just in time to see the thing leering down at him. He screamed.

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His head swam as a number of things happened in what seemed to him to be all at once. He was cold and he felt like his clothes were all wet; it felt like the time one of the big kids at the park had thrown him in the river when it was cold out, but for some reason he hurt everywhere and couldn't seem to move. There was something in his throat and no matter how hard he tried, he couldn't swallow it or spit it out, and trying to talk around it just made his throat hurt more.

"We didn't … door was open." Rex could hear voices that he knew belonged to his parents, brother and the lab tech, but all he could see was blurry lights that were too bright and made his eyes hurt. "Heard a thud … Lobo was already on him."

He knew he was missing parts of sentences and couldn't figure out why, but a very blurry head he recognized leaned over him. "Stay with us, Rex."

Papi…? "You're going to take a little nap now mijo," – mama? – "and when you wake up you'll be all better." She gently ruffled his hair as a plastic mask covered his face and he suddenly felt sleepy…

He didn't feel cold anymore when he woke up. "I'm so sorry, hermano," César's voice said from somewhere to his left, but he couldn't open his eyes or turn his head that way. "I didn't think it would get this bad." He wished he could reach out and hug him. It hadn't been his fault he'd wanted to look into the box after all… had it?

"Let him rest," there was guilt in the lab tech's voice. "I'm being reassigned. They want me to perfect the Lobo so this… doesn't happen again."

Rex was starting to doze off again when he heard something that made his heart pound and a monitor somewhere near his head sound. "Maybe it's for the best, Jer… Dr. Van Kleiss. This is all our fault after all…"

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His heart was racing when his Nanites had processed the gas enough that he woke up. Cold sweat clung to his skin and matted his hair to his forehead, and for one brief – horrifying – moment he was alone, and then her hand was on his shoulder and she was asking if he was alright. He forced himself to take deep, even breaths, just like he had when they were giving him the gas, and nodded, one of her hands reaching up to ruffle his hair. Just like mama and César used to do…

And Van Kleiss, an evil voice in the back of his head reminded him. He shuddered at the thought and she draped her lab coat around him thinking he was cold. For some reason it made him smile, though it faded when César came into the lab. The dream had seemed too real to be a figment of his imagination, but how could his brother have… how could it be real?

How do I know if I can trust you, César? He thought as their eyes met, and for a moment when he saw the look on Rex's face, he saw a flash of something that made his stomach lurch uncomfortably: guilt. No…