A/N: Another prompt fill: "bruce and nat working out the lullaby mechanism?"

Because as always, I will love Brucenat to the ends of the Earth.

The first time it happens, it's three months after the fall of S.H.I.E.L.D., they're on the outskirts of Prague, and the team most definitely did not call for a Code Green.

And yet here Natasha is, scaling the side of the 'abandoned' warehouse like a… well, like a spider, and slipping in through the window. She shoots three of the Hydra thugs before they can even react, somersaulting further into the room to avoid fire from the fourth, before she takes him out as well. She pulls out her batons and is in the process of knocking out two young men (enhanced, stronger than normal) when there's a roar outside.

"Guys?" she asks. The comms have been silent; unless she somehow didn't hear it, no one said Bruce should enter the fight. Swearing, Natasha starts going on autopilot, barreling through waves of Hydra soldiers and having almost no trouble taking them all out. She grits her teeth as one manages to get a lucky shot on her leg, but she shoves the pain into a corner and continues to fight.

"Who's covering first floor?" she calls.

There's a moment of static, then: "I've got it, Nat."

Thank god. At least she doesn't have to worry if the rest of them are doing their job right. "Clint, thanks for answering. Anyone have eyes on Banner?"

"Yes," says Tony. "Don't worry, he's juggernaut-ing his way through the right people, I promise. He… might've gotten shot, though."

"Fuck."

"Pretty much."

"As long as he has something to do, we can deal with that later," Steve says. "For now, we need to focus on getting to the center of this place. Hopefully the scepter will be here."

They continue with their plan: infiltrating the base from all sides and all floors. The Hulk continues to fight Hydra forces outside, oblivious to how the rest of the team is currently trying to meet in the middle. Natasha almost wants to take a breath of relief when she finally reaches Steve's side, kicking yet another soldier in the face. If there's one thing that avenging does wonders for, it's her endurance. She wasn't always so used to long term fighting.

Stark blasts his way in after the rest of them, taking out the last of the thugs. He does a quick scan and quickly determines that the scepter isn't here, while Natasha removes a data stick from her belt and begins downloading Hydra's intel. Clint moves back to where she had been to retrieve the enhanced that Natasha had been fighting before.

"I've got all their files," Natasha says. "Drained them like a vampire draining blood."

"I'm not going to comment on how creepy that metaphor was," Tony begins.

"Except you just did," Natasha mutters.

"But we have to find a way of dealing with Bruce. So far we've gotten lucky and the bases have been isolated, but Prague isn't that far away, folks. Thor, you up for containment?"

"If I must," Thor says. "I should be able to draw him away from the city."

"This is ridiculous," Natasha proclaims, removing her data stick and putting it back in her belt. "There's got to be a better way of getting Banner to calm down."

"Knocking him unconscious?" Steve tiredly suggests. "Easier said than done. Plus, he won't exactly like it."

"Neither would you," Natasha says. "That's not what I meant."

"Look, let's just start with getting him away from civilians," Steve replies. For some reason, he doesn't seem to be in any mood to fight her. "Then we can discuss this again."

Moving the Hulk goes about as well as expected. Thor gets punched several times for his trouble, Tony makes some comment about Bruce that only seems to piss the Hulk off more, and Natasha mostly wants to bang her head against a tree at her teammates' attempts. Clint is (wisely) staying out of it, and Steve is somehow just getting ignored by the Hulk (like the Hulk respects him too much to attack him, but refuses to take orders, either).

He hasn't seen Natasha yet. She's been staying in the trees up above him, hoping that he doesn't decide to rip one up because really? That would suck. A lot.

When the Hulk punches Thor halfway to kingdom come (again), Natasha decides that she's had enough. She scales carefully down one of the trees, slow enough that the Hulk notices her approach and pauses in his raging to observe her curiously. He grunts and throws a boulder over his shoulder, but otherwise is just eyeing her warily.

"Look, Stark can be an asshole," she starts.

The Hulk huffs. Maybe he agrees. Huh.

"But he means well," she continues, softening her voice. "He said you got hurt? Well, you hurt those bastards back. Good job. Wound's healed too, I bet."

The Hulk stares at her, but he doesn't move. Natasha dares to take a step closer, aware of her teammates' presences in a circle around them, watching and waiting.

"You're probably getting tired, right?" she suggests. "I mean, smashing's fun and all, but it's also exhausting. At least, for me it is. First thing I'm gonna do when we get back to Stark Tower is crash for a good ten hours. That sound good, big guy?"

The Hulk roars at her, looking indignant, but then he actually sits down. And he stays sitting down, as if he's waiting patiently, until an hour later he shrinks back to Bruce.

Bruce, who immediately notices Natasha standing a few feet away, and that the rest of his teammates are approaching. Natasha watches his hand involuntarily twitch towards his heart, which confirms her suspicion: it had been a kill shot. No wonder the Hulk came out.

"So I don't know what the hell just happened," Clint proclaims. "But oh man, Bruce, it was a sight to see."

The polite knock at the door of her apartment rules out Tony (he doens't know what knocking is), Clint (he has her permission to not knock), and Thor (he shouts through the door). Which means it either has to be Steve or Bruce.

Steve went to meet up with Sam an hour ago, which means it can only be Bruce.

"I don't have food," she tells him flatly.

He blinks, surprised. "That's… I don't… I don't go scavenging for food at two in the morning."

"The other night you were digging in the fridge for leftovers until you had to give up and make oatmeal because you forgot to eat dinner and didn't take any of Tony's pizza."

Bruce raises an eyebrow. "I don't want to know how you know that."

"Probably not." She grins. "What can I do for you, Doc?"

"Look, um…" he gestures past her. "Is it alright if we talk…?"

Natasha steps aside to let him in, and the door slides shut behind him. She offers him a cup of tea, which he declines, before sitting him down on her couch and seating herself a few feet away from him, watching him. He does his customary twisting-of-the-hands thing for a while before he speaks.

"I remember a couple of things from the other day," he begins. "And… I do remember you, talking to me. It's… it was… better, than the stuff the others do. I was surprised, and I'm not sure why he responded to you any better, but I was wondering if…"

"You want my help with post-battle transformations," she surmises. It's not the first time she's thought about this.

He nods.

"That wasn't guessing," she admits. "It involves… making myself look non-threatening. I knew what I was doing. You're right; if we could somehow solidify it, make it a routine…"

He smiles. It's a rare sight. "Glad you caught on."

"I'm glad you're willing to trust me with this. When do you wanna start?"