“Uh, Control, we might have a problem,” Clint said into his comm.

It wasn’t often he admitted to problems—mostly because he could usually fix them before they got to that point—but bulldozing over this particular one seemed like a really poor choice.

“Explain,” Coulson’s voice crackled through the line.

Clint leaned against the doorframe of the shady little safehouse bathroom, arms crossed, trying to find the right words.

“So, uh… we’re gonna have to call off the op. Turns out, the world’s deadliest assassin can’t handle, well, altitude.”

He let that one sit for a second.

Clint Barton had seen his partner do a lot of impressive things in their time working together. He’d watched her take down five guys twice her size without breaking a sweat, slip out of handcuffs like they were friendship bracelets, and lie so convincingly that even he started second-guessing reality sometimes.

What he had not seen, until today, was Natasha Romanoff curled around a toilet in a high-altitude Peruvian safehouse, looking like she was about to topple headfirst into the porcelain.

From the bathroom floor, Natasha made a weak, unamused noise that might’ve been an attempt at objection if she wasn’t currently occupied dry-heaving into the toilet. Not that there was anything left for her to throw up. She’d emptied her stomach hours ago, but her body didn’t seem to have gotten the memo and was still dedicated to the cause.

“How bad is it?” Coulson asked.

Clint glanced back at Natasha.

“I mean,” he said, scratching the back of his head, “unless you’re cool with her conducting an arms deal from the floor of some cartel bar while trying not to puke on anyone’s boots, I don’t think the meet’s gonna happen.”

Coulson sighed. “Did you try the Diamox?”

“That, the ibuprofen, the caffeine, the dexamethasone. None of it worked.”

More silence.

Then, as if Clint didn't know: “It’s a critical op.”

SHIELD had been chasing this asshole for months, and Strike Team: Delta had been slotted in as the grand finale. But Clint also thought that propping Natasha up and wheeling her in like it was Weekend at Bernie’s wasn’t exactly going to inspire fear in their target. Especially once she inevitably faceplanted into said drug lord’s lap.

“The mission is time-sensitive,” Coulson added, which—yeah. He got that, too. That was why he’d personally doped Natasha to the gills. But alas, in vain.

“So’s Nat’s ability to stay conscious,” he shot back. “We’re not hitting that meet, Phil.”

There was another pause, this one longer.

Then, “Get out of there.”

“Copy that,” Clint said, clicking off the comm. He turned to Natasha, half-conscious on the floor.

“Good news,” he said, as cheerfully as possible. “You don’t have to put on makeup.”

Natasha turned her head just enough to glare at him. Her face was a pale grey, except for the deep shadows under her eyes and the angry flush across her cheeks. Beads of sweat lined her forehead.

"It's not funny."

Clint held up his hands. “Never said it was.”

Natasha let out a slow, shaky breath and dropped her forehead back onto her arm. “Altitude is stupid.”

He eyed her a little more critically. “How bad’s the dizziness?”

She didn’t answer, just dragged one hand over her face in an exhausted attempt to block out the dim bathroom light.

That bad, then.

“One to ten, how likely are you to pass out if you try to stand?”

There was a long pause, then Natasha lifted two fingers. Weak, wobbly, and not even remotely convincing.

Clint raised an eyebrow. “Uh-huh. You’re a really bad liar when you’re sick. That looks more like a seven to me.”

"And feels like a twenty-eight," she admitted.

They sat there for a while, Natasha taking slow, deliberate breaths while Clint kept watch—less for actual threats and more to make sure she didn’t pass out and crack her skull open in the process.

Eventually, she mumbled, “I should be able to push through it.”

Clint laughed outright. “Nat, you can barely sit upright. I don’t think the Peruvian drug cartel is gonna be too intimidated by you crawling after them on all fours.”

“They’d better be,” Natasha grumbled, although without much conviction.

“Tell you what. Let’s get you down a couple thousand feet and you can bust their asses from the safety of a nice, oxygen-rich altitude. Sound like a plan?”

Natasha grumbled something unintelligible.

Clint took that as a yes.