Author Note – this can be read independently or as an off shoot from When The Call Comes, as both assume Natasha and Bruce had contact after AOU and Natasha knows he went to Asgard with Thor.

Disclaimer – I don't own, just borrowing.

Those Left Behind

The sound of muted gun fire draws Natasha's attention from her tablet as she walks down a corridor. She stops and lifts her head to look around. The noise stops and restarts seconds later and she realises the sound is emanating from a room she just passed. She backtracks and peers into the open doorway to find a woman sitting huddled in her coat in front of a computer in a previously unoccupied office. Natasha recognises her immediately but Betty pays no heed to Natasha as she lingers in the door; she's so absorbed in the footage on screen she hasn't noticed the retired assassin. She's tempted to back out before she's seen, wishes there was some way to avoid the inevitable awkward introduction. She's rooted to the spot as Betty replays the clip that had been recorded during the fight for Sokovia. She doesn't know by who, but it was shot at a distance either from one of the life crafts or the helicarrier. The screen had been zoomed in so close it was almost blurry with pixels but she could make out the moment she approached the Hulk in the abandoned playground. Natasha watches herself hold up a hand to the Big Guy, her breath catching when he goes to do the same. He was going to let her perform the lullaby. She stares unblinking as the hail of bullets rain down from the QuinJet and she's knocked to the ground. The Hulk's roar bellows from the speakers as Ultron flies off. He quietens seconds later and tenderly lifts her unconscious form into his arms and launches them into the air. She looks away as they soar out of shot and Betty moves to replay the clip again. Natasha looks about the room and spies a box brimming with personal affects and a potted plant discarded on the otherwise empty desk. Obviously, Betty was moving in and had plans to stay.

Natasha lets the clip end before she clears her throat and knocks a knuckle against the door to alert the other woman to her presence. Her head snaps up, startled by the interruption and Betty reminds Natasha of Bruce when she used to interrupt his lab time as she turns and blinks in surprise. Then a look of recognition dawns on Betty's face as her eyes flick between Natasha and the screen. Betty slowly rises, her hand pointing limply at the computer.

"You're…"

"Natasha Romanoff," Natasha finishes for her with a nod, stepping into the room. "You're Doctor Ross."

"Betty, please," the brunette insists sweetly. She glances distractedly over her shoulder. "I never thought Bruce would ever be able to…the way you helped him…It's fascinating."

Exhilarating, breath taking, intimate. Instead of voicing the words, Natasha settles on, "That's one way to describe it."

"Thank you," Betty says, and to Natasha's surprise the appreciation is genuine. "I know how stubborn he can be when comes to accepting help."

The woman spoke confidently from experience, one they share. Natasha won't, can't, divulge any details of what transpired between her and Bruce. It's too personal. Her throat still catches when she thinks of him. Betty's feelings for him a clear as day on her face and Natasha is jealous that she is able to love freely rather than reserving it only for the three children who call her Aunty Nat.

"It was necessary," Natasha tries to shrug it off. It had been but it developed into more than that and surpassed any of her expectations. What had initially started out as a method to help him, ended up affecting her just as much.

"He made a lot of progress since the last time I saw him," Betty nods in agreement. She eyes Natasha again. Closely, the former spy realises, as if she was seeing past Natasha's mask. "Johannesburg would have been hard on him."

It tore him apart. After a few years living a relatively stable existence in the Tower Bruce had managed to regain some of the confidence he lost while he was on the run from Ross. He just started to rebuild a life and re-establish ties to the scientific community, most of whom welcomed him back with open arms, some out of fascination with the Big Guy but he had been amazed by the number of people who came purely out of admiration to pick his brain about his scientific work. He had hope for the future, one Natasha wanted to be a part of. The fallout from Johannesburg obliterated all of that. If he returned to find Betty at the Facility, he may choose differently. He was and will always be in love with Betty, while he most likely assumed their feelings started as a by-product of the Lullaby.

"He needed time," Natasha says knowing the other woman would understand her underlying sad tone. Betty nods in agreement, her sympathy clear. A sudden need to divert attention from herself forces Natasha to address the scientist. "I don't mean to seem rude, but why are you here? I got the impression that you disagreed with your father about Bruce."

"I do, I do," Betty stammered. "I'm not naïve enough to think my father has given up on the Hulk. In fact, that's how he pitched this job to me, by talking about the success the Avengers had with him and asked me to help build on that."

"Bruce isn't here," Natasha tells her keeping a neutral tone. Ever since Ross mentioned Bruce during the initial meeting about the Accords, Natasha suspected he was working on a way to draw Bruce out of hiding or at least learn more about the Lullaby. Betty's presence and explanation confirmed that suspicion, but Natasha was still undecided whether she was complicit in her father's plan. The aging Secretary of State probably expected to lure Bruce back with the promise of working with Betty alongside the Avengers. He wasn't coming back. Bruce won't return from Asgard unless it was necessary.

"No but you are," Betty argues back eagerly. She gestures at the computer again. "I would love to talk to you about-."

"No," Natasha refuses harshly and Betty is taken aback by her forceful interruption.

"You have no reason to trust me, but I just want to help," Betty starts apologetically. "Bruce, I mean. I know what my father wants to do. Believe me when I say I want nothing to do with that. When I heard about what you could do I thought there might be a chance."

The woman seems earnest enough but Natasha had known many liars. She wasn't about to trust her with her experience of the Lullaby when she didn't know her. Especially with how awkward it would be when Betty realised how tender the act was. "A chance to do what?"

"Cure Bruce," a frown accompanies the answer as if it were obvious.

It was Natasha's turn to frown. "What makes you think Bruce would survive anything the Hulk can't?"

Blunt but not unkind. It's as hard for Natasha to voice it as it is for Betty to hear it, but it's the truth. Natasha wishes she had Betty's optimism. Unfortunately, the woman opposite her hasn't given up hope on saving Bruce. And Natasha doesn't want to dispel any notion Betty has that Bruce feels the same way. But short of finding a way to kill himself, the best Bruce can hope for is control of the Big Guy. Neither woman want that. Natasha would feel the loss either way, she's grown attached to both of them. Natasha waits for a response as Betty glances away, her eyes sheening over as the realisation dawns on her.

"Am I interrupting?" Stark asks as he fills the door way. Neither woman look at or answer him so he pushes further into the room and addresses Betty with his usual hyperbole. "Dr Ross, good to have you with us but I need to borrow Romanoff for a mission briefing. I would prefer we just wing it, but your dad's a stickler for briefings."

Betty acknowledges him with nod and a forced smile. "Of course," she agrees.

"I'll drop by when we're back, hopefully you'll be settled in." Betty nods her head and Stark whirls to face her with a knowing, mocking look before walking toward the door.

Before following, she catches Betty's eyes again and the other woman nods again. Reassuring, commiserating, dismissing all in one glance. Natasha acknowledges the dismissal by turning to follow Stark as he lingers in the hallway. Natasha makes it half way to the door and turns on her heel.

"Just so you know, Bruce is safe. Your father can't get to him." It's cryptic but it's all she'll say. She wishes she wasn't compelled to console the other woman and herself with this information. She tries not to think of moment before Bruce left with Thor; of how he cupped her cheek to draw her to him; of how his lips felt when they touched hers; of how he whispered 'I adore you' before he turned to stand beside Thor. She tries not to think he would have said substituted another word for 'adore' if Betty had been in her place because she would have said it back.

"Are you sure?" Betty asks and Natasha nods. "Thank you," Betty says again, genuine as before. "You didn't need to tell me that."

"I know," Natasha agrees. "It's just…I would want to know," she explains meaningfully. She turns around and joins Stark in the hall before the brunette can respond or question her further. Natasha keeps walking, leaving Stark to trail behind her.

"That wasn't awkward at all," Tony whispers sarcastically once they're out of Betty's earshot. At least he is making an effort to be tactful for one of them. Natasha shoots him a dirty look which he just laughs at. "What? It's every man's dream to have women fighting over him and Banner's not even here to appreciate it."

"What the hell is wrong with you?" She hisses at him as he backs up in surrender, smug grin firmly in place.

"Determining that would require many hours of introspection and therapy. But in my defence, Bruce refused to let me lie on a couch and talk through my problems after that one time."

"He's not your therapist Stark," Natasha pushes ahead to press the call button. "And we weren't fighting. If he could choose, it'd be her," she sighs.

"I think you're selling yourself short," Stark replies with uncharacteristic sensitivity. While he has it in him to be generous, he just does it without his usual fanfare, it's rare for him to go out of his way to make people feel better. As they step into the empty elevator, she prepares herself for the Steve-like talk she senses he's gearing up for. "Don't undermine what you have with him. You gave him a way to cope, Natasha. He'll always be grateful for that."

"Look, I'm not going to tell you he doesn't care for her because he does and always will. But Bruce knows that's in the past. He can't have the life he wanted with her."

"So he chooses me by default? You suck at this Stark," she tells him and looks to the floor. He's trying, but it's not helping. Does she really seem so pathetic that Stark feels the need to reassure her?

"Give me a chance, I'm out of my comfort zone here," he throws up his hands in mock exasperation. "She knew him years ago, before all of this. She wants that Bruce. You understand who he is now, probably more than he does. He feels the connection you have." Pause. "Yeah, you're different from her. She has hope and a fantasy. You give him hope in his reality. Took me a long time to figure out reality is better than any fantasy." She's not convinced but she's touched by his words. "He usually cuts all ties when he runs, he didn't with you. That means something."

"What makes you think that?"

"You," he answers simply. "Your flirting sucks when it's for real."

"Gee, thanks," she smirks sadly. After a moment, she adds, "Really, thanks."

His head bobs a couple of times. "So, how did I do with the pep talk? You know, because I've been practicing in the mirror."

"I'm sure you have," she rolls her eyes. "Needs a little work, better you're getting there. Add a head tilt, work on your tone and you'll give Rogers a run for his money."

"Let's not go too far now, I'm just a substitute while the old man is elsewhere." She smiles with him as he laughs, deep and real, ending with a little sigh. She knows he misses verbally sparring with the other man, misses the camaraderie they both denied. He may never admit it but he regrets losing Steve's friendship. They fall into silence as they ascend toward the briefing room. Just as the elevator slows, Tony breaks it. "You know she'll be gone before we get back."

"Probably."

Natasha has her doubts but she doesn't voice them. They were both left behind by the same man and while their beliefs differ, she feels an affinity with the other woman. She doesn't know what Bruce would make of their meeting, only knows he would feel as awkward as they do. Natasha would never make him choose, she would walk away before it ever came to that. She tries to keep hold of Tony's words, Bruce only kept in touch with one of them. He ran from Betty to keep her safe, he was going to run with Natasha to save her from her past.