Hi, I'm MoonstoneRain and I'm nervous as all hell. It's my first time posting here and my first time writing Avengers fanfiction…be kind please? =)

Rating is T for the usual—some violence, mostly off-screen depending on where I take this, kissing, bits of dirty humor here and there, the occasional swearword, some sex references (most of which can be blamed on my attempts to keep Tony Stark in-character).

Disclaimer: I don't own the Avengers. Casey is my own creation; the rest belong to Marvel. Any song lyrics or quotes you may recognize, you may safely assume that I don't own those, either.

Chapter 1: Just Another American Saturday Night

Bruce Banner sighed heavily and pulled off his glasses to rub his eyes. Of course, this would have to happen tonight. Tonight, when Tony Stark came back from a long, unwelcome, probably borderline-violent meeting with Fury, he would find a badly failed experiment in his and Bruce's lab.

Well, let's look on the bright side, Banner comforted himself. It could've gone much worse.

He looked over to the underlying cause of his exasperation, a very pretty girl—a very young, very pretty girl, twenty-one and a junior in college, to be precise—and thought dryly, At least you managed not to turn her into a hulking rage-beast as well.

The girl, whose clothes and face were still covered in fine green dust from the exploded beaker, started slightly when Bruce looked at her. "I'm sorry, Dr. Banner—" she began timidly, but he cut her off.

"Not your fault, Casey. I'm the idiot who told you to take it off the burner." He sighed. "Well, come on." He stood up and nodded towards the lab door. "Let's get you cleaned up before something really bad happens. For all we know I have poisoned you."

"I doubt that, Dr. Banner. Unless you were seriously lying to me, last I checked you were trying to reverse the effects of your exposure to radiation, not replicate them."

"Yeah, because these things always have the exact results you're expecting," he snorted. Working with Tony Stark 24/7 really honed a person's sarcasm skills, whether this was their intent or not. "Come on," he said again, nudging his relatively new intern to the door. "I don't want to take any chances."

His brief sarcasm seemed to have cowed the brief spirit that had flared up in the girl when she responded to his crack about poisoning her. Now she quietly obeyed his instructions and went into the bathroom/locker room that Tony had insisted on putting in just down the hall from the lab when he found out that the intern Bruce had so grudgingly taken was a female.

Once she was inside, Bruce sighed and put his face in his hands again. Why did he even bother trying? He knew by now that he was never going to find a cure for the "Other Guy," and he sure as hell knew better than to try to do so with an innocent bystander in harm's way. Suppose—he shuddered at the thought—the experiment had resulted in his becoming Hulk permanently?

The image of the girl's broken, twisted body at his feet, amidst the wreckage of a completely totaled lab, flashed through his mind. He shuddered again. No, that could not happen.

Right. No more experimenting, especially not with her around.

While Bruce wouldn't exactly say he was in love with his new intern—or "infatuated," as Steve and Thor insisted on calling it—he was certainly attracted to her. Then again, he was also attracted to Thor—not that he'd ever admit that to anyone—and he'd once had a dream about Natasha that had haunted him for weeks and made him devoutly thankful that Clint wasn't a mind-reader. Then there was all the (unintentional, he was certain) flirting that the ever-oblivious Tony kept throwing at him…

Okay. It had been quite a while. That was obvious. But it was no reason to behave like an animal—Bruce internally snorted at that image—by hitting on this girl, this pretty, readily available girl who Tony swore on Coulson's soul was attracted to Bruce (not that Bruce himself was even remotely sure of that) and putting her in a compromising position.

Casey Kyle, a double major in biology and, for some unfathomable reason, visual art, had responded to Tony Stark's call for interns three weeks ago, and both Tony and Bruce agreed that she was the best go-for they could've obtained. She was whip-smart and a fast, efficient worker. (Though why Tony had thought they needed another person in the lab was so far beyond Bruce he didn't even bother questioning it after a while.) Problem was, she was into environmental science and human anatomy rather than physics and chemistry, which sometimes resulted in…well…situations like this.

What had happened tonight was a typical disaster. Bruce had given Casey what he hadn't realized was an unclear order. He'd told her to turn off the burner, which she had taken as "remove boiling mixture from heat." When she'd put it down (because, obviously, she couldn't hold the damn thing forever), she'd put it down on…well, Bruce wasn't sure, but it was clearly an explosive, whatever it had been, because the pot had exploded and the sluggishly-boiling mixture had turned to fine powder. They'd both probably inhaled it and Bruce could only pray that his half-finished cure had been harmless.

Which, as Casey had astutely pointed out, it should've been. It had been intended to negate the negative qualities of something else, not enhance or, God forbid, replicate them. But still. The explosion itself could have caused serious harm…

Casey emerged from the bathroom, having changed from the jeans and button-down shirt she wore to work in the lab into one of the vintage-style dresses she wore on the street. "I'm sorry, I—I didn't bring any other clothes," she stammered when she saw Bruce's raised eyebrows.

He waved a hand dismissively. "Don't worry about it. Hey…" He leaned forward, locking his eyes on hers. "Don't blame yourself. This was my fault. You're gonna be okay, we're both okay. You got me?"

She nodded shyly. "I'm so—" she began, but he cut her off.

"No. No apologies; it wasn't your fault so you have nothing to apologize for. Now, do yourself a favor. Go home, get some rest, and let me straighten this out with Tony, all right?" He saw the doubtful look in her eyes. "Go on," he urged her. "You shouldn't have to worry about this."

She sighed and pushed a lock of hair from her eyes. "I…I still think I should have known better than to—"

"No," he cut her off again. "You're not a chemistry major; you probably haven't even taken chem, have you?" At her head shake, he said, "Well, there you go. I should've been more clear. So, again I say: no blaming yourself. Got it?" This time she nodded, and he smiled encouragingly, hoping to earn a smile from her. He didn't get it. "Okay, so…" He cast around for a way to dismiss the girl without making her feel unwanted. "Go get some sleep, do whatever; I'm sure you've got classwork to finish. I'll let you know when to come in tomorrow." He rolled his eyes. "Or should I say, Tony will let you know in the most obnoxious way possible when you should come in tomorrow."

That elicited a small laugh from Casey. She looked up at Bruce through her eyelashes, and he wondered for the fiftieth time if she had any idea what kind of effect that could have on a man. "Well…thank you for letting me go early," she said shyly. Three weeks and she still seemed intimidated by his presence. Bruce often comforted himself by recalling that she seemed equally intimidated by Tony, leading him to believe that it was their brainpower that cowed her and not their ability to kill her suddenly and violently at their discretion.

Which, of course, Tony would never do, and Bruce would never do if he could help it. He had to believe the Hulk liked her, at least a little…and what happened next, what always happened when she left, seemed a good reason why:

"Goodnight, Dr. Banner." Casey smiled a little, and blushed when she said, as she looked straight at Bruce's chest, right where his heart would be if she could see it, "And goodnight, Hulk."

Something inside Bruce twitched, and he almost laughed, as he had the first time she'd done that. The fact that she acted as though the Other Guy could hear her was not only amusing, it was downright adorable. He contented himself with a smile and a, "Goodnight, Casey."

When she left he sighed and looked at the mess they'd managed to make in the lab. It was going to be a long night. And when Tony got back, he'd have some serious explaining to do.

Casey Kyle dragged herself up two flights of stairs, down three hallways, and into a room that looked more like the Batcave than the dorm of a college girl. Between her comic-hero-plastered walls, inventions (and parts of inventions) scattered over the desk, shelves, and floor, and the pile of camera equipment in one corner, the whole room looked like the lab of a young-at-heart scientist.

Casey sighed and collapsed on her bed without so much as taking off her coat. So, she'd screwed up again. But he'd been so nice about it. That was it—Dr. Banner was always so damn nice about everything. Why was he so kind to her? Why didn't he just give her the standard "You careless head-in-the-clouds worthless moron" lecture that she so easily earned from everyone else? She knew he went far too easy on her. If it had just been Stark working in that lab, she'd probably have been fired by now.

She closed her eyes. Tears were forming at a rapid rate, and she was afraid that if she didn't calm herself she'd end up bringing the posters on her wall to life again, like she had when she'd found out that her supposed prince charming was cheating on her. She really had to get that under control. No sense in bringing the stupid nosy government into it…again…

Mutant, they'd initially called her. Mutant, indeed. The only thing she was good for was hiding and working for other people. If she could just keep from drawing attention to herself…that was good enough for her.

A hand rested on the center of her back and she jumped in terror. She sat up straight, fearing the worst—she'd either brought the posters to life or she'd managed to animate her body pillow, an experience she desperately wanted to avoid repeating—but she immediately relaxed when she saw that it was neither. She'd just woken her unofficial, non-college-sanctioned (non-college attending, for that matter) roommate.

She smiled and leaned her head on her best friend's shoulder. "Hi, Loki."