She was there to make sure Tony Stark kept out of trouble. He was a force to be reckoned with at times — in simpler terms, a major pain in the ass — and it made keeping an eye on him for S.H.I.E.L.D. incredibly difficult, but what Natasha Romanoff hadn't expected was that she was the one who would get herself into trouble.

She was standing outside what she would find to be his spacious and lavish bedroom. His big birthday party was tonight and that was sure to be… entertaining at least. Natasha — known as Natalie tonight — sucked in a breath, looking down at the watch case she held in her hands. Going undercover as a personal assistant to Tony Stark of all people was taxing but if her job was to keep him happy, well, she would keep him happy.

"Do you know which watch you'll wear tonight, Mr. Stark?" she asked as she made her entrance, heels clicking loudly against the tiled floors.

"I'll give 'em a look."

Not looking up, Natasha heard the dull tone of his voice. His usual enthusiasm and cocky sense of humour was gone. He'd quickly closed his shirt upon her arrival, but Natasha had already seen the damage the arc reactor was doing to his body. Things were looking grim, and they both knew it. Or Tony knew it, and Natasha simply observed from a distance.

"I should cancel the party, huh."

Natasha glanced over her shoulder at him. She had been silently fixing him a drink and now held the martini glass delicately in her thin, pale fingers.

"Probably."

"Yeah, 'cause it's, um…"

Natasha continued forward. "Ill-timed?"

"Right, sends the wrong message."

She glanced up and down his chest, knowing Tony would never even know that she knew. Natasha glanced up.

"Inappropriate."

Tony just looked at her, taking a nervous sip from the drink she had just given him. Something passed between the two of them and even Natasha could not tell exactly what.

"Is that dirty enough for you?"

She hadn't meant to say it out loud. She was too used to using her sexuality against men. But Tony Stark wasn't her mark. She wasn't here to manipulate him or seduce him, merely assess him. And, of all people, it was Tony Stark. But it came too naturally to her, almost like a second skin she wore over the real woman deep down. But she was supposed to be keeping a close eye on him, it made sense to keep him close, by whatever means. Natasha was rationalizing it all, she realized.

And then Tony seemed to snap out of whatever trance he had entered while staring at her, forcing out his words almost as if he were flustered by what had just transpired, as momentary as it had been.

"Uh, gold face, brown band… the Jaeger, I'll give that a look. Bring 'em over here."

Natasha turned away with a smile to retrieve the requested watch while Tony went to set down his drink and take a seat. She returned to his side in an instant while Tony, despite his peeve of being handed things, took the box from her hands.

"I'll take that, uh, why don't you—"

She sat down on the arm of his chair with a soft sigh, regarding the man before her curiously. Her green eyes seemed to bore into him and Tony found himself staring again. Natasha suddenly reached down, pulling out her liquid foundation from a clutch she had been balancing in her grasp the entire time, then gently dabbed at Tony's bruised face with it. He turned his head to the side, allowing her the access she needed. He was surprised by her light and unexpected touch.

They exchanged glances once more before Tony tilted his head toward her again.

"I gotta say, it's hard to get a read on you… where are you from?"

"Legal," she replied simply, her expression remaining entirely neutral as if she hadn't just expertly evaded his question. She continued dabbing at his bruises, the makeup slowly blending in with his skin, making the damage look a lot less severe than it was.

"Can I ask you something… hypothetically?" Tony asked suddenly. Natasha sat back, regarding him in such a way that said she was listening.

"Bit odd," Tony admitted, rubbing at the bridge of his nose, showing his obvious stress and uncharacteristic weariness. "If this was your last birthday party you were ever going to have, how would you celebrate it?"

Natasha's features remained impassive but her gaze flicked away briefly while she considered the surprisingly genuine question. She could lie, she thought, and just tell him what he wanted to hear. But then she realized her answer wouldn't be a lie, not really. There was some truth to her next words, as honest as she could be under the circumstances.

"I'd do whatever I wanted to do," she replied seriously, "with whoever I wanted to do it with."

She stood, readying herself to take her leave, when suddenly Tony caught her arm. He didn't grab her, just tugged enough to get her to stay. Natasha might have stiffened but she didn't. Instead, she turned back to him.

"Is there something else, Mr. Stark?" she inquired with a raised eyebrow.

"Yeah, uh, yeah there is."

Tony's eyes stared into hers and Natasha was caught off-guard. There was so much pain in his expression, so much uncertainty. He knew that fate was testing him, testing his genius, seeing if he could somehow cheat the inevitable. And in that moment, he looked vulnerable. He finished his drink in its entirety then stood, placing his hands on Natasha's arms.

Then he kissed her. It was over as soon as it had begun. The hunger she felt as his lips met hers was suddenly replaced with doubt. He stepped away suddenly, looking almost apologetic. Natasha wondered if any woman had ever seen him look that way before.

Speaking of inappropriate…

"Mr. Stark, are you sure this is—"

Tony ran a hand through his hair and Natasha noticed how endearing it was to see it all ruffled and standing up on end.

"No, no, this is all wrong… I shouldn't… the party's about to start… and Pepper…"

She let him mutter to himself, trying to solve some internal debate that she was glad she had never had to experience herself. He was seeking pleasure, she knew that. For Natasha, she took what she wanted when she wanted it and it was always easy enough. Willing partners were not hard to come by. And she had no attachments that stopped her from doing so. The rest of the time, it was just work. Right or wrong, she pushed it aside and kept it locked away where the turmoil could not reach her. So she stood there, waiting for Tony to either dismiss her or give in to himself.

He chose the latter.

Natasha found herself more responsive than she would have expected. Her hands found their way up to cup his jaw, pulling him toward her, encouraging him every step of the way. Never would she have dreamed that she would be kissing Tony Stark of her own accord. The thought, even minutes earlier, would have repulsed her. But she had seen something in him — a longing to not be alone while he was in a dark place that he could not share with anyone. Anyone but her, although he was completely unaware of her knowledge. He might be aggravating and stubborn and self-absorbed most of the time, Natasha knew, but even Tony Stark had layers, just like her. And for some reason, he had let her see them.

He pushed her back onto the bed, the hem of her dress sliding just up her thighs an inch or two before Tony paused, looking into her eyes again. Natasha had never taken him for the shy sort. She knew he had a long track record with women who showed up in the evening and were escorted out in the morning. But, she supposed, he didn't have intimate talks about his rapidly ending life with those women.

"Natalie, I—"

"Shh," she whispered, cutting him off.

And so she found herself being the one to guide him. She allowed him to get close to her in a way she allowed so few. Natasha couldn't help it — she had seen into his eyes and she felt sympathy instead of disgust. She knew S.H.I.E.L.D. was working on a way to slow down the process that was slowly destroying his body but even they could not engineer a cure. Only someone like Tony could come up with a permanent solution. And how much time did he have left? She didn't pity him, that wasn't why she was doing this, but she understood where this was coming from. And, inexplicably, she wanted to help him find at least some solace before having to face the unknown by himself.

If only it weren't so dangerous to get close to people, to become attached… maybe Natasha would have done the same thing, if the situation were reversed.

He never took his shirt off, not surprising Natasha in the slightest. Her dress was easily discarded in moments, tossed aside in a haphazard heap somewhere nearby. Tony only left her side once, to close the door, lock it, and he only spoke again to disable JARVIS, freeing them from any interruptions. Tony Stark could be late to his own party. After all, would anyone really be surprised?

Tony knew what he was doing. Once he set aside all reservations about what they were getting into, he started exploring with his hands and mouth, touching Natasha in places she had not been touched in awhile. Not with the same tenderness Tony seemed to be offering her. In that moment, she was not the seductress Black Widow, she was just Natasha Romanoff, surprising herself with every little hitch in her breath when he found a spot that delighted her in all the right ways.

She helped him with his belt and that too got tossed away while he quickly found his way out of his pants. At first she let her fingers drift across his hips before cautiously sliding upwards, under his shirt. Natasha only went so far, however, knowing he'd pull away before she got too close.

And then they were together, intertwined with each other so suddenly that Natasha wondered if she were actually dreaming, about to wake up back in the nearest S.H.I.E.L.D. facility on a hard bed in an impersonal room that only served as a place to crash for the night. But when she closed her eyes for a second, then opened them again, she was still there, still with him in the closest way possible.

And she didn't give it a second thought.

As time moved forward, the braver they each got with one another. With each thrust, Tony leaned in closer to her, and Natasha even went so far as to nip at his ear lobe teasingly. Her arms were pinned beneath his hands and her legs were wrapped around his waist. And when they both came, Natasha could not help but let the pleased groan escape her. Everything was still after that. Tony looked up, into Natasha's eyes one last time, and she brushed a sweaty lock of hair off of his forehead.

Then she remembered: she wasn't Natasha Romanoff. She was Natalie Rushman. None of what had just happened would amount to anything because she was not real to him. She was a figment that she had planted into his imagination. And now she was compromised. She had let herself do something wholly unbelievable and incredibly stupid. No one could find out — not Coulson, not Fury, nobody.

"Mr. Stark, you have a party to attend," she reminded him, batting her eyelashes when all she wanted to do was close herself off.

She had thought she had been doing this for him, but Natasha didn't do anything selflessly. She had stepped over a line, she had been foolish to allow Tony Stark anywhere near her. God only knew what he would say to everyone—

"Uh, right, um…" He pulled away when she released him, instantly searching for his pants. "Let's just keep this between us, yeah? No need to incite a one woman riot out of Pepper."

He was almost sheepish now. Natasha knew very well that Pepper was wary of the spy's presence, almost eerily so. The other woman was perceptive, Natasha would give her that. But she was grateful. Natasha sat up, swinging her legs over to the other side of the bed where she too stood, collecting her garments off the floor, sliding back into her dress gracefully and running her fingers through her hair to smooth any unruly tangles. Her heels, abandoned earlier on, were within reach and she sat down only to slip them on before standing, running her hands over her dress once, and moving to leave.

"Mr. Stark," she said politely, her voice void of any lingering emotion.

"Natalie— uh, Miss Rushman," he quickly corrected, trying to find some façade of professionalism.

Natasha — or Natalie — only glanced back once. For all his annoyances and vices, she suddenly couldn't fault him entirely. It wasn't just the sex, she knew that. Her view of him had changed and she wasn't entirely sure she knew or liked how it had done so. But, as she let herself out of the bedroom, the sound of her heels retreating the only indication that she had ever been there at all, Natasha could not find a single bit of regret for what had just occurred.

Her own emotions were a mystery she would have to figure out for herself later on. For now, she had a mission to oversee and complete as objectively as she possibly could.

Author's Note: I had this nagging urge to write this after watching Iron Man 2 again and seeing the sexual tension practically dripping between these two. I wanted to write a scenario where it had amounted to something but what exactly, we don't know. This is intended as a one-shot but I'm not sure how I want to leave this just yet.