How does Loki's mind control work exactly?
Your eyes turn an unnaturally, bright, blue, and suddenly it seems you've become a mindless drone.
But it's actually really not that bad (though a certain hawk would fervently disagree). You retain your personality, memories, knowledge, and skills, and you're perfectly aware of everything you're doing. This is not a total puppet and puppet-master kind of situation. One thing does change however, and one might say it's the most important thing- your reason for living.
When Loki had first appeared in the heart of the SHIELD base, with a glowing scepter in one hand, Clint's thoughts went something along the lines of: Shit! Tesseract exploded! Ahhh! Alien intruder, alert! ...The guy looks like a fucking zombie...and what's with the wizard staff?
"Please put the spear down!" Nick Fury had demanded...politely...sort of...well, he said please. Uh... don't think that's gonna work, boss.
Then the maniac started shooting blasts of blue energy all over the place, and leaped (and holy shit he could jump pretty damn far) onto SHIELD agents who were trying to gun him down. Alright, he has a freaking magic stick. Okay. Dead agents. Just another day in the job.
Then Loki shot a big, blue, ball of energy at him, and he was forced to throw himself aside to avoid it. He scrambled back onto his feet as quickly as he could, which was apparently not fast enough, because before he could straighten up, Loki was a mere four feet in front of him.
FUCK!
Loki looked at him with an unbalanced look in his eye, "You have a heart." Um, what?
As the scepter tip touched his chest, fear and panic melted away, and a sense of icy clarity washed over, sharpening his mind.
His name was Clint Barton. He only took orders from the man in front of him, Loki, and suddenly his gun had no business being in his hand.
But just because Loki was king now didn't prevent Clint from having his own thoughts.
"I come with glad tidings," Loki said, taking a few strides around the room, "Of a world made free."
"Free from what," asked the SHIELD director.
"Freedom. Freedom is life's great lie."
Crazy talk is coming out of your mouth, sir, Clint thought, which of course he didn't say out loud because of course Loki wouldn't like that. Plus, there were more pressing matters at hand, like the build up of tesseract energy that was threatening to blow everyone to kingdom come.
After expressing his concerns, Loki gave him a curt "Well then", and Clint whipped out his gun to shoot Director Fury in the chest. It wasn't that they had some mind-reading mojo going on, simply that Clint was now so attuned to Loki's needs that he could deduce what Loki wanted to happen, and it was his job to make it happen.
From there on out it was all generic action movie material with wild driving and gunshots, Hill and a small army of SHIELD agents on their heels. Clint steered past bullets and flying cars like nobody's business because hey, it was part of the job description. They managed to escape the underground tunnels and get onto the road before the SHIELD base detonated behind them.
Clint continued driving along the asphalt for a while, the only sound was the crunching of gravel beneath tires. The silence was a tad awkward especially since there had been explosions and yelling just a few minutes ago. Clint wondered if he should turn on the radio, before remembering that there was only a police scanner on the truck.
He sighed. A master assassin and an astrophysicist in the front seat and the god of mischief in the back, it was like a setup for a bad joke.
"I need somewhere secure, inconspicuous, preferably with a lab," Loki said, out of the reticence.
"A lab...?" Clint trailed off, remembering Dr. Selvig sitting next to him, "I know just the place, sir."
And so began Clint Barton's (not-so) fabulous adventures with Loki.