How they had ended up being the only two left in Stark Tower, they did know. How the rest of the situation had happened though, neither had a clue.

It had all started after Captain America and Black Widow had brought down S.H.I.E.L.D and HYDRA with it. With all her covers blown, Natasha had taken up Tony's offer of staying at Stark Tower until things died down a bit. The other Avengers, bar Thor who was still on Asgard, had all come along as well for a bit, Clint escaping a blown mission in the middle of god knows where, Bruce lured in for a bit of science work and Steve followed Natasha, still not sure what to do but looking forward to catching up with the team.

They had all stayed for a few weeks, catching up on their time apart and as much as Tony complained, they knew he loved having them all around really. Stories flowed freely between them, nothing was considered classified anymore so they could tell all about what happened although Clint and Natasha still wouldn't tell a curious Tony what had happened in Budapest.

Secretly, Tony was jealous. He was convinced something romantic had happened in Budapest and he was determined to get to the bottom of it, no matter how much it may hurt him to find out. Truthfully, all the little stories and comments between the assassins and the closeness of them hurt. He wanted to be the one sharing those stories and memories and being the one that could convey their thoughts or ideas to Natasha with a single glance.

But he never said any of that or let any of it show. He was just the genius, billionaire, playboy, philanthropist, Natasha would never want to be with an egotistical asshole like him when there was her partner that saved her life and always had her back.

But then the change came. First Clint had to leave to deal with some HYDRA agents, Natasha would have gone with him but she was a little too well known at the moment and Clint had it covered himself. Bruce heard of a medical emergency that he had to hurry to so he was flying off around the world and Steve had gotten a lead on the winter soldier and he was off following him. Once again Natasha was going to go but Sam Wilson had decided that he wanted to join Steve to catch up and it was only a two person mission to avoid too much publicity.

They had all left within a week leaving a rather bemused Natasha and Tony behind, suddenly rather alone and with not a lot to do. It wasn't like they hadn't been spending time together but, since Natasha's time working as Stark's secretary, they hadn't spent any time alone. Now, they were faced with no one to distract them, neither was quite sure what to do. See, both Natasha and Tony were secretly in love with each other but they were both convinced that the other wouldn't return their feelings.

Natasha, being the professional spy that she was, buried her feelings deep down and decided to try and ignore them, hoping that they would go away soon enough. She couldn't love Tony Stark, could she? He was childish and annoying and ... and ... oh god! He was sweet and kind when he wanted to be and she really didn't need to be thinking like this. It didn't matter what she may or may not feel anyway because he would never love someone like her. Even if he did have a serious relationship, there was always his perfect CEO Pepper or some other perfect girl that wasn't broken and damaged like she was.

Anyway, he didn't trust her as far as he could throw her thanks to her lies as Natalie Rushman. He seemed to have taken the deception to hear and was actually genuinely upset and distrustful after it and Natasha didn't blame him. She had become his personal assistant, in record time because she was good like that, and he had trusted her to handle his life whilst he dealt with things like dying and stuff like that. No, it would never happen so Natasha buried her feelings deep down and drew on her acting skills to act as normal as she could.

Tony was a pretty good actor himself what with faking a smile and politeness at all of those press conferences and god forsaken board meetings. He had developed a mask from a very young age to hide his true feelings, his hurt at his father and the loneliness his genius and attitude brought him, so he also knew how to mask his feelings for Natasha. He too was convinced that the spy could never love him. His reputation preceded him and he was well aware of the fact that he was an egotistical asshole the majority of the time but it was all a mask to protect him. When someone got to know him and he let them in, he showed his true self; sweet, kind, caring and generally concerned for the other person.

But that would never happen with Natasha. He convinced himself it would be wrong, she was his teammate and a spy that had lied to him in the past, he shouldn't trust her, let her in to see the soft underbelly under the hardened shell of snark and sarcasm, but he couldn't deny that he had fallen hard for her.

The two inhabited the tower for the next few days without really crossing paths, it was big enough for that to happen and both had bits and pieces that they were doing. Come Friday night, however, they both found themselves in the common area of the tower, crashed a little too close on the couch. Friday evenings were the times the team tended to keep free to chat and watch films and this Friday, it seemed that it was to be no different.

After a few minutes of polite chatter about what they had been doing over the last few days, they put a film in to watch. It hadn't been awkward per say but it wasn't the normal flowing chatter that it had been. With both hiding their feelings, it made the chat very closed off from each other so as not to give the wrong impression or let anything on.

If they were being honest, neither really knew what was going on in the film, let alone what it was called, both were initially too aware of the closeness of the other but slowly, as the film progress, they grew more and more tired.

Natasha had had several late nights of contacting Steve and Clint in different time zones to keep up on the latest information and both were still busy and wouldn't be returning for a while. She had also made brief contact with Bruce just to check in on his status but he was so busy trying to help that he just made a quick acknowledgement and assured her that he was fine before going again.

Tony, being the genius that he was, had spent several late nights in his workshop, beavering away on new inventions and improvements to the suits and as such had lost track of time leading to little sleep and tiredness that hit him like a sledgehammer. Sat on the couch, he could feel his eyes drifting closed, but was startled awake briefly by the feeling of a heavy object on his shoulder that hadn't been there a moment before.

Turning slightly, Tony could see a head of red hair slumped on his shoulder and a fairly peaceful face, suggesting that Natasha was asleep, not that Tony thought she would do anything like this awake so he let himself enjoy it in his tired state and slowly drifted off, his own head dropping softly to rest on top of Natasha's.

The next time the two awoke, it was almost simultaneously to the rather noisy end of the film. Natasha's face had become more snuggled into Tony's shoulder and his arm was now around her shoulder. Noticing their position, both tried to leap up and away from each other embarrassedly, but they only succeeded in bumping heads and ending up in each other's personal space, faces mere inches apart, breathing slightly heavier than usual.

As Natasha's green eyes stared deeply into Tony's brown ones, they both felt the connection zapping between them. In the haze of half sleep and tiredness, they both found themselves leaning in closer and closer until their lips touched. That sparked them off and soon their lips were moving frantically against each other's and the pent up emotion released suddenly, neither noticing JARVIS turning off the TV screen and dimming the lights down (JARVIS knew of his creator's love for the spy and had a soft spot for her himself).

The next morning...

Natasha awoke to daylight streaming through a window. She hadn't slept that well and without nightmares for ages; she figured that she must have been so tired that she passed out asleep. Opening her eyes slowly, she was confused though, this wasn't her room and whose arm was that around her waist? And, hang on ... was she naked?

Freezing in place, Natasha tried to remember what had happened last time. She and Tony had been sat on the couch and had put a film on. She remembered feeling really tired and then it hit her and she remembered it all. Falling asleep and waking up on Tony's shoulder with his arm around her and then panicking, trying to get away but ending up closer to him than she started. And then they kissed ... after that it was all a blur but now she was pretty confident of whose arm it was.

Moving as little as she could, Natasha rolled over, coming face to face with the man she had fallen in love with, Tony Stark. For a minute, Natasha begun to snuggle back into his embrace before she realised what she was doing and froze again. She couldn't do this. This was a mistake and it could only have been a one night stand to Tony. She needed to escape before this got and more awkward than it was already going to be and maybe, just maybe, they could both pretend it never happened and she could go back to burying her feelings.

Just as Natasha began to wriggle away from Tony, his arms dragged her flush against his body and his face buried in her neck.

"Going somewhere?" a rough voice sounded, the vibrations felt against her neck.

Natasha froze for a third time and silently cursed the engineer for choosing this one day to wake up early. In the silence following, Tony raised his head to look her in the eyes. Seeing her walls down, her panic and surprise hurt him deep in the gut. She was just going to sneak away and ignore him like this was absolutely nothing to her. Well shit!

Hope you liked it. I've kinda fallen for Tony/Natasha recently so there may be a few like this. Unbeta'd so sorry for the mistakes.