Disclaimer: I wish I owned Captain America ;) (or Black Widow for that matter, I love them both)
She sees it in Steve's blue, blue eyes when he opens his mouth – that he's about to make a confession of what he thinks he feels for her (which is most definitely not real, because love is a myth, told help children sleep at night – sweet dreams, darling, and never wake up). And so she tells him the only thing she can, to make him stop.
"I killed him."
Steve pauses in confusion, and she thinks angrily, stung, that maybe this statement doesn't alter his perception of her at all – because she's killed so many, what's one more in the scope of things?
So she elaborates.
"Your friend. Junior Juniper. I shot him, I stabbed Dugan, I might've killed Peggy too if I'd had the chance. (She expects the hit about his first love will set him straight if the one about his friend doesn't.) Why do you think the name of Juniper's killer is stricken from the records? I wasn't always straight. I wasn't always a redhead. I was a killer, blonde-haired, doe-eyed, face of an angel and I lured them in – oh look, a child, a damsel-in-distress – and I killed them. I was an assassin – highest number of hits, wasn't I proud? – and so I was given the mantle of Black Widow, given my new identity and new hair – red for the Red Room, red for blood, red for the ledger I'll never wipe out."
"I thought you were -! How are you so ol- how could you have been alive then?"
She wants to curse. It's been years since she's made any sort of slip up and of course when she was trying to dissuade him she hadn't thought first and it had just come out. Of course he'd latch onto that – he didn't know, none of them did, except Fury and maybe Clint though he'd never confronted her about it. She sighs, and decides she may as well continue seeing as the cat is out of the bag, so to speak.
"Red Room serum. Not quite as good as yours but it did the job – you saw that with James." (Yasha, her mind whispers traitorously – she still hadn't told Steve, after he'd come to her wretched with the knowledge that the Winter Soldier was his childhood best friend James Buchanan Barnes, what she'd found on her own files – that she'd had her own name for him: trainer, partner, lover.)
He seems a little dumbfounded, too shocked to speak, and she smiles a little, wryly; she would never have guessed that her age of all things would be the what stumped Captain America. (Honestly, she's not that old – he's still got a good decade or two on her, the hypocrite.) She reminds herself of her intent to discourage him, and thinks now that perhaps he will be hurt by her lies and this will be the end of it. (For some reason, that thought hurts her a little – she will miss fighting alongside him if he leaves, she thinks; he's a good partner, that's all.)
The silence lengthens and, because she's too much of a coward to look up and see his face, she turns and leaves. (A part of her cracks when she doesn't hear his footsteps behind her.) But she is Black Widow, and she never fails, so she walks on.
She's just made her way to Fury's office (she doesn't quite know her way around all of the rooms in Tony's ridiculous new building yet) when the speakers crackle on and she hears Steve's voice.
"Natasha Romanoff. Natalia Romanova. You have been a part of SHIELD for - years. You have saved countless lives. You have a vital role as one of the Avengers. Yes you were an assassin, a murderer – but thanks to the war, so was I. You did what you were trained to do – no more, no less."
She freezes in anger and embarrassment. So he's trying to tell her she has a soul – idiot! And now he's tied his name to hers, in front of all these agents (who incidentally, are now gaping shamelessly at her), like a complete and utter fool – how does he know they're all trustworthy? (She ignores the voice reminding her that all the people here have been thoroughly vetted by each of the Avengers, and JARVIS to boot; it's still a foolish move, regardless.)
Steve chooses that inopportune moment to wrap his arms around her and she instinctively reacts, kicking and punching and flailing, but he is more than ready for her and blocks her every move (perhaps he knows her better than herself) and in that moment she is crying and angry (but she is made of marble, she never breaks, says the cold voice of Madam.)
"Red is your colour, and for good reason – it is the colour of fire, of passion, of love –"
(When could announcements be made through comm mikes anyway? Didn't they have to be made in the announcers' room – oh wait, Stark tech.)
" – and I love you".
At that she fights all the harder, twisting and clawing and writhing, biting like the Black Widow she is, but he doesn't let go and when he swoops down, in the salvation of his gentle kiss, she is broken.
A/N: If you are a Marvel fan and haven't watched Agent Carter, go watch it! I promise, the only regret you'll have is that there isn't a third season (though I live in hope).