Warning: language, drug use.

Edited to fix formatting errors that resulted from posting at 3:00 in the morning.

I don't own the Avengers.

Clint "Hawkeye" Barton had not slept in just over four days.

It wasn't the longest he'd gone without sleep. In fact, it was about average. Four or five days of being awake, followed by a night of "sleep", rinse and repeat ad infinitum.

His insomnia had started shortly after the Chitauri invasion. He had found himself lying awake at night, restless, heart pounding in his chest against an ever-tightening band of anxiety that crushed his ribs and made it nearly impossible to draw breath.

At first, he was confused—What the fuck is happening to me?—but it didn't take him long to figure out what was going on. After all, panic attacks weren't exactly a rare phenomenon.

That sleep—or the idea of sleep, even—could cause such a reaction was troubling, but also not too difficult to explain.

His mind had been invaded, his body used against his will. As little more than a puppet, and with no control over his actions, he had attacked those he had sworn to protect. He had aided a megalomaniacal demigod who sought the subjugation of all mankind, and in so doing he had been instrumental in the deaths of many, many good men.

Phil Coulson had been a good man.

And thus was born the stalwart refusal to surrender control of his body, even to his own subconscious.

It was irrational. He knew that. But that knowledge didn't stop his hands from trembling as he layed in bed at night, didn't stop his panicked gasps for air.

The clear solution, he figured, was to just never sleep again. A quick internet search revealed that this was not going to be a successful tactic—the longest anyone had been recorded to go without sleep was eleven days. And going longer than two or three days was directly correlated with massive decreases in cognitive function.

He was an assassin, first and foremost, and he kind of figured he needed his ability to concentrate.

So he was going to need a better plan.

When you kill people for a living, you meet all kinds of unsavory types. It wasn't hard to find someone who could provide him with what he needed. With some experimentation, Clint found a way to sleep as little as possible while maintaining a level of alertness that allowed him to perform his job to the exacting standards required of him.

There were some hiccups.

For example, he didn't sleep for the first week. That had been the goal, of course, but after three days of no sleep, he had become irritable and easily frustrated. By the fifth day, that had evolved into outright aggression. On day seven, he spent four hours in the dead of the night, in SHIELD's physical training facility, screaming incoherent accusations at inanimate objects and beating on anything that would stay still and let him.

He learned an important lesson. He went to his supplier the next day, nursing his bruised fists and a headache the approximate size of Mt. Everest, and made a request. The man had made a joke about a two-for-one special he gave all the speed freaks, and had handed him the diazepam with a knowing smirk.

Clint hated him.

After that, he made it a point to try and sleep at least every four days. With the Valium, at least, he could make it through the night without throwing up, although he wondered how restful his drug-induced sleep was. It didn't matter, though, really. It was enough.

It was, unsurprisingly, Natasha who noticed that something was wrong.

"You've lost weight, Barton," she'd said one day, after they'd finished sparring. He looked down, and noticed the way his previously-tight uniform hung loosely from his shoulders.

With a shrug and a laugh, he'd replied, "You know I have to watch my figure, 'Tasha. Carbohydrates go straight to my hips."

She'd smiled, and they'd changed topics, but she hadn't stopped thinking about it. He might joke about carbohydrates, but the fact was that Clint couldn't really spare the ten or so pounds he had lost. Something about the situation was nudging against her intuition, and she always trusted her gut. She resolved to keep an eye on him.

It only took a day and a half after that for her to learn Clint's secret. Once vigilant in ensuring that no one find out what he was doing, he had become increasingly sloppy. Indifferent, even.

She watched him in the locker room, barely making an effort to conceal herself, as he rifled around in his bag at the end of the day. His actions became more and more agitated, until his hand closed around something. When he pulled it out of the bag, she saw that it was a pill bottle. He uncapped it, shook out a few tablets, and popped them into his mouth. He took a swig of water from a bottle, and tossed the pills back into his bag. Leaving it lying open on the bench, he headed into the men's room.

Natasha took that as her opening. Looking to make sure no one was watching her, she slipped over to where Clint had left his bag, grabbed the pill bottle, opened it, and took one. She pocketed it and left.

When she asked Dr. Banner if he could identify what the pill contained, she could tell he was confused. Sure, it was within his capabilities to do such an analysis, but SHIELD had a whole department of chemists who would have been more than happy to help. Still, he agreed to do it. He liked Natasha, and something about the way she had asked had seemed...desperate.

She got a text message from him the next day at work that simply said, "Dextroamphetamine, amphetamine." Her heart sank.

Natasha was not one to waste time. She considered texting Clint to ask where he was, but decided to maintain the element of surprise. Instead, then, she triangulated his cell phone signal. She was unsurprised to find that he was on the roof.

She was surprised to find that he was doing paperwork. "You know, Barton, we have these things called 'offices,' where there are 'desks,' on which we can write."

He shrugged. He was sitting with his back to her, shoulders hunched.

"Clint," she said, all traces of humor gone from her voice.

He turned to look at her.

"Why are you taking amphetamines?"

That was unexpected. Although, he thought, it really shouldn't be. 'Tasha had always been whip-smart. If someone was going to figure it out, it'd be her.

He knew that she would know if he lied to her. And they had too much history together, and too much respect for each other, for him to even try it. So instead he said, "I can't sleep."

"No shit, dumbass. Dextroamphetamine and amphetamine are stimulants."

"No, I mean...I can't sleep. I can't."

It clicked for her. "You're afraid to go to sleep. Because of...what happened with Loki. Right?"

He nodded. She felt a rush of something—pity, maybe, or sympathy, or something else soft— that she crushed and compressed into anger. Now was not the time for gentleness.

"And this was your brilliant idea? Abuse stimulants so you never had to go to sleep again?"

"Don't be ridiculous, Romanoff, I sleep. Sometimes. If I—" he cut himself off.

Natasha had, in her line of work, accrued a decent amount of information about drugs and addicts. She knew there was a pattern that a lot of stimulant abusers followed. "Please tell me you're not taking benzos too, Clint."

He averted his eyes in lieu of an answer.

"Christ, Barton!" Natasha exploded. "Are you insane? Do you know how dangerous that is?"

It wasn't something he'd considered too closely.

After a moment, she said quietly, "You're an idiot." Then she was walking away from him, no, stalking away, hurt and anger and disappointment stiffening her posture into something feral.

Clint Barton had not slept in just over four days. He reached into his pocket and pulled out his bottle of pills.

Why not make it five?