"Ok, what now?" Bruce stood on the sand looking at Natasha.

They were about a kilometer north of the cabana, still on the west beach of the island. They had hiked away from their supplies and shelter for their first practice session.

"Now you get mad." Nat crossed her arms and watched him dubiously. She didn't know if he could do that. I'm always angry, he had said in New York, but she knew that wasn't true. She knew only a few things really got him going. She was one of those things.

"And then what?"

"I take your pulse. You tell me how you feel. We see where your threshold really is."

"And if I go green?"

"I ask him if he's ok with this. See what his triggers are, what makes him shift."

"Won't he be a bit pissed for that?" Bruce asked dubiously.

"He hasn't been too angry the last few times I've seen him," Nat replied thoughtfully. That wasn't exactly true—she remembered their first encounter on the island, his glowering face staring up at her perched in the tree above. But then the next day, he had been calm. And just the day before, he was calm again. He liked the island, she realized. He had been mad when she disrupted his time there—who wouldn't be? But he wasn't just uselessly rageful every time he was out. Just at the beginning, since rage was what usually triggered him. He didn't like staying that way though.

"Ok, I feel like that's a big gamble to take," Bruce said, his voice still doubtful.

"I can handle him. Now stop delaying." Nat walked towards him and he backed up quickly. Nat froze, embarrassed.

"I'm just gonna take your pulse. Jeez, calm down." Nat tried to not let any red creep into her burning cheeks. Banner also reddened, but he allowed her to approach. She took his wrist in her hand and pressed two fingers just below his palm. His skin was surprisingly soft, the hair on his arm downy. After a moment of searching she found it. His pulse was quick, thrumming. She closed her eyes to concentrate on it, trying to count.

"Well?" Bruce asked.

"Are you trying to get mad?" Nat replied.

"I mean, yeah, kinda."

"Well, try harder." Nat looked at her watch. It matched her gauntlets—a nice touch from Tony.

"You know, 200 beats per minute is dangerous," Bruce pointed out. "They say that the maximum heartrate someone should ever hit is 220 minus their age. That means I should never be above. . ." he trailed off.

"What, afraid to let on how old you are? I already know you're a geezer," Nat teased. She felt his pulse spike as she spoke. He was hovering around a hundred beats per minute. "You've got a ways to go if you're going for green," Nat reminded him. Another minor spike as she spoke.

"I'm sorry, I'm just—this isn't really a stressful environment."

"Do you want me to help?"

"Not really."

"I feel like I've gotten good at making you mad these days," Nat smiled.

"I know. That's why I don't want your help. You start talking and he's bound to come out."

"I don't mind his company."

Bruce raised an eyebrow and looked at her dubiously.

"What?! He's pretty chill recently, he likes the island, he lets me enjoy my peace and quiet."

"And I don't?"

"I mean, our quiet isn't really peaceful," Nat pointed out. She felt his heartrate rise with that one. Abruptly, he yanked his wrist out of her hand.

"I don't like this, it's like you get to have this conversation with a polygraph on me. No fair."

"Ok, what do you propose? We use the jets biometrics and risk you smashing it to pieces?"

"Ya know, you seem really attached to that jet considering you never seem to plan on using it."

"When I get in that jet, it's a one way trip, and you're coming with me," Nat snapped back. Bruce glared at her. In their banter he had almost forgotten her intent for the exercise.

"Doesn't Steve need you for something?" he asked grumpily. "I'm sure Sam and Rhodes are beating on him every day without you there."

"He'll be ok. He's a tough cookie." The sarcasm dripped from her voice. "Now stop delaying. Let's do this." She held out her hand again expectantly, waiting for his wrist. Bruce didn't offer it.

"I'm sorry, I just think that this isn't going to work. I don't want him to come out right now. I just want to be for a while. I don't want to worry about all that."

"You always worry."

"I mean, yeah, but this is just, I mean, it's like tempting fate."

"I think that's the very definition of what it means to be an Avenger."

"I'm not an Avenger," Bruce corrected.

"Ooh, this is good, keep going," Nat said excitedly, beckoning him to continue. He just looked at her, his frustration obvious. Nat huffed.

"Ok, fine. We need another way."

"Another way of what?"

"Getting your heart rate up."

"I'm not running, if that's what you're implying."

"No running, promise," Nat held up her hand like she was taking an oath. Suddenly, she had an idea.

"I have another way in mind," she said, her voice suddenly husky. With a turn of her head and a shift in her weight, Nat was abruptly alluring. She looked at him through her lashes and bit her lip, the image of seductiveness. Bruce blanched.

"No. No, no, no, no, NO," he stuttered. "Natasha, come on now, don't do this," he backed away from her, his hands up.

Just as quickly as it came on, Nat let it drop, and suddenly she was just her casual self again, t-shirt and shorts and athletic, ready stance. Bruce shook his head.

"How do you do that?" he asked.

"Why do you ask? Did it work?" There was a twinkle in Nat's eye as she asked. She knew it worked—it always worked. Bruce scratched the back of his neck and refused to meet her eye.

"I think—ya know what, I just—I think this is a bad idea. Maybe we were a bit ambitious with this plan. I think we need to try something else."

"So it took you approximately ten minutes to quit." Natasha's voice was flat.

"No! I'm just not in the mental place for it right now."

"So get there," Nat snapped, her eyes steely.

Bruce looked at her, serious. She could see the gears turning in his brain—he wanted to prove her wrong, but he also didn't want to do this. She watched as spite won.

"Fine. Piss me off." He stepped back and crossed his arms, not breaking eye contact.

"Are you sure?"

"Yeah."

"Ok," Nat said. "I just want you to know, before we do this, that I don't mean what I'm about to say."

"Yes you do. That's why it'll work," Bruce-smiled bitterly. Nat grimaced. She didn't like where this was going.

"Johannesburg," she began slowly.

"That's guilt, not anger."

"The way Wanda just walked up to you and got in your head like it was nothing? That's guilt? You say all the time that you're a liability and wow, you most definitely were that day. There's a gym at the tower for what, decoration? For Thor to show off every time he visits? A few hours a week and you could have had her pinned, but no, some waif of a girl shows up and suddenly you're green and tearing up a city."

Bruce kept his arms crossed, still looking at Natasha. She felt herself settling into the cold calm of her interrogation technique. She looked in his eyes and saw everything he was feeling—he was an open book. Seeing that guilt, the impatience, the anxiety, it tripped her. She was used to steely, cold, uncaring subjects. Bruce was none of those things.

She wracked her mind for what to say next. She had trained for this—for cruelty. Why was it so hard now?

"Thor would decimate you in battle. Mjolnir could take you down," she hesitated. He didn't care about that. Who was the mightiest or strongest or most worthy were things that Cap and Thor cared about, not Bruce.

"Oh c'mon Nat, don't get soft on me now," he teased. Nat gritted her teeth. She wanted to piss him off, not hurt his feelings. And everything she was thinking of—his lack of self-esteem, his passivity, his loneliness, his aching desire for things to be ok—was what made him who he was. She couldn't tear that apart. The goal was anger, not existentialism. She loved those parts of him—she didn't want to attack them. She silently cursed.

"Yesterday. You let me shove you off," she jabbed. She watched his eyebrows rise, surprised she would mention that. She was surprised too. "You gave up—just like that. Why are you so afraid? You claim to have these convictions, right? So have them."

That one struck a nerve. She watched his jaw twitch. She was transported back to Clint's house—the quiet upstairs guest room, with the powder blue bathroom and the windows letting in late afternoon sun.

"Go after what you want. And don't say it's another PhD. Make a move, Bruce. Stop being afraid of your own life—it's gonna happen no matter what. You can't run from it."

He was gritting his teeth now; Nat could hear the grinding sound of enamel on enamel. She felt her heart skip a beat as she realized what she had to say next.

"You thought you'd hurt her," Natasha started slowly. She only knew the most basic outline of Bruce's life before the Avengers. "Thought she couldn't see past the green. So you left. How fucking easy. What a cop-out. Blame it on the big guy."

"That's enough," Bruce hissed. He shut his eyes tightly, his brow furrowing. Nat watched him, trying to drink in every detail.

His veins seemed to grow and darken—were his shoulders widening? No green though. He breathed in and out, in through the nose and out through the mouth.

"Let me take your pulse," she stepped closer, but he turned away, shutting her out. She could see it in his temple, throbbing.

In a moment it was over. A few more breaths and she watched the tension flow out of him. His shoulders sagged.

"What did you notice?" she asked tentatively.

"Anger." He replied tersely.

Nat bit her lip. Bruce took a breath, calming himself.

"He's in there," he continued. "I don't think he's mad though. I could just. . . feel him more."

"That's good, right?"

"I don't know."

"Well," Nat paused. "Should we try again?"

"I think I got it this time," Bruce replied.

"Ok, but let me take your pulse. If you go green I can handle it."

Bruce gritted his teeth. She knew he wanted to say no, to protest her nonchalant treatment of the other guy. He didn't though, instead just holding his wrist out passively. Nat grasped it and rooted around for a moment until she found a soft spot where she could feel his blood rushing beneath the skin.

His pulse was racing. Nat closed her eyes and concentrated, felt it rising beneath her fingers. She opened her eyes and peered at her watch, trying to simultaneously count and keep track of time. He shot up past 130 beats per minute, 140, 150, 160. He yanked his wrist back and walked briskly away from her, up the beach. Nat watched him walk. The back of his neck was green, his left shoulder lopsidedly swollen, larger than his right. As he walked it went down, the green retreating back to his veins.

"Wow, Bruce. That was good. Really good. I saw—you kept him at bay."

Bruce sat down on a massive driftwood log and put his head in his hands. Nat walked up and sat next to him. She didn't say anything, letting him calm down. Eventually he spoke.

"I don't like this. What are we learning? That when I get mad, the Hulk comes out? Big surprise there."

"You had just gone past 160 bpm when you pulled away. We have an idea of where the shift might take place now."

"How do we know it was the pulse and not the anger?"

"We don't. Not yet at least. We can separate the two though."

"I said no running," Bruce reminded her. "You promised."

"Fine, no running. How do you feel about kickboxing?" Natasha asked. She tried to quash the tightness in her chest. You promised.

"If I kickbox right now I'm just going to get mad again."

"Ok. So we take a siesta and come back in a few hours. Sounds good to me."

Nat jumped to her feet and walked away quickly, leaving Bruce speechless behind her. She didn't want him to see the look on her face. Hurting him like that had been harder than it should have been.

They did go back in a few hours. Nat taught him the basic steps, a few jabs and kicks, and then did some figures with him. When he was sweating and exhausted, Bruce sat down and drank some water and realized that while he could feel him, the Hulk wasn't threatening to burst forth. He was just there. A little closer, perhaps, but there.

And so they began their real work; raising his heart rate, allowing the Hulk halfway out, not angry, just there, then Bruce re-asserting himself and calming back down. A couple times he got nearly halfway through a shift—ripping a few shirts along the way—before returning to himself. Slowly he grew more confident, more trusting of his own ability to regulate. He exchanged words with the Hulk once in an awkward transition state and Nat was almost gloating. Everything was great—the three of them were finally talking. Until it went too far.

It was four days after they had started his training in earnest. They had taken to kickboxing in the morning—Nat would teach him new things each day, they'd do reps of the figures he had learned so far, then they'd spar. The kickboxing was reliable—it raised Bruce's heart rate, and he was learning some valuable hand to hand skills he never had before. He didn't say anything, but Nat's jab about the Scarlet Witch taking him down so easily had gotten under his skin. He threw himself into learning with an attention she hadn't expected from a middle-aged lab geek.

They were having fun with it, the morning he did go green. They had started getting lazy in how far away from the cabana they walked—maybe only a half-kilometer, so it was still in sight in the distance. They were laughing, Bruce trying to uppercut Natasha and failing miserably. She never went easy on him. She'd allow him his slow practice hits to get the motion down, and they'd do reps for him to get the fast-twitch motions, but every time they sparred she just took him down unapologetically. This time in particular, he had started tickling her every time she pinned him.

She wasn't really that ticklish—she could ignore it if she wanted, but she didn't want to. It was nice hearing Bruce laugh, and being close to him, and being touched. They jumped back up, still giggling, and she got in ready stance. So did he, but after she landed her first blow on his bicep, he just exploded. It happened before either of them knew what was happening.

The Hulk roared and lunged at Natasha. She ducked, but his swatting hand caught her hip and threw her to the ground a few feet away. She twisted her gauntlet and tased him, once, twice, three times. On the third one he stayed down, convulsing on the sand. Natasha sat up and rubbed her hip—she was going to have an ugly bruise. The Hulk lay there, panting, but didn't make an effort to get up.

"I'm so sorry. I'm so so sorry, I didn't want to do that. Are you ok?" she asked. Before he could roar in response or attack again, the Hulk started shrinking. Bruce was back, less than a minute after going green. He groaned and curled up tightly on the sand.

Natasha was simultaneously ashamed of their laziness in not walking further from the cabana, and relieved. She had to hold Bruce up to walk him back to their campsite, his legs weak as jelly from the repeated tasers. She forced herself to walk evenly, despite the fact that her left hip made a strange grinding sound every time her leg moved forward. It radiated heat and pain into her body. They didn't talk as they walked, both shaken. They had been growing confident, even cocky, with their training. This was a definite knock.

It took some convincing the next day to get a very sore Bruce back out to the beach, but Natasha managed it. She didn't mention her hip, and with some painkillers and anti-inflammatories from the jet she didn't even have to limp. Bruce was utterly convinced that he could never work with the Hulk—not if a change could happen with that little warning. Nat was hard-pressed to come up with a counter-argument.

She was silently relieved for the lapse—it meant she could justify staying longer. The way he had been improving, she had been planning on only staying a few days more. She didn't want to think of their island time ending, but she could feel the pull to get back stateside. She didn't want to turn on the comm unit and get a lengthy lecture from Steve or Fury, but she was also worried she might miss something important. She'd kick herself if a crisis happened and she wasn't there to help. Working with Bruce was important, it was what she wanted to be doing, but duty called. She just needed him to feel the same way. And that sudden shift, right when they were finally starting to get along, to work together towards a shared vision? It threw a wrench in that.

Bruce was even more convinced he would never go back to society again. He was also relieved; maybe now she'd believe him. Silently, he was almost afraid she would give up—their days together had become fun. If she didn't think he was going back, she'd leave him there. She'd go back and stay faithful to her personal moral compass, and he'd have to do his best to follow through on his. His was seeming less appealing, however, if it meant watching her go.

After a day off they kept training, more tentatively, more safely, but still playing with fire, tempting the Hulk and sending him back inside. There wasn't another lapse like that one, but the Hulk was angrier the next few times he got to half-emerge. Then he calmed down, almost sullen, refusing to speak to them at all. For Bruce, it was a victory. For Nat, it was concerning, but she let it go, glad that Bruce's confidence was bolstered.

They ate rations from the jet, and Nat figured out how to catch fish from the tide pools south of the cabana. They feasted on the fruit the island grew and figured out new ways to eat the potatoes and other roots Nat had bought at the market, what felt like forever ago.

They built fires each night and played cards together, swapped stories of Tony and Cap being ridiculous, testosterone fueled maniacs—who they both also cared for very deeply. Nat talked about the algorithms she had used to find him, and Bruce broke down for her what he knew about the science behind making Vision—Nat had always been curious about it, but Dr. Cho was back in Korea and Tony was apathetic about it at best. She wasn't close enough with Vision to ask, and watching him with Wanda always put an unsettling feeling in her stomach. She left them alone in lieu of her lonely computer most nights back at HQ.

Days blurred together and time passed quickly. Soon, it had been two weeks of training. There was an easy-going rhythm to their dynamic—one based on clear, unspoken rules. They never talked about their pasts. Natasha knew Bruce had loved someone, a woman named Betty, but she had never met her, and he didn't want to talk about it. She had prodded him on it to get him mad that first day of training, but she never mentioned it again, afraid it would become a schism between them, an awkward, irritating barrier. He didn't ask about the Red Room, about her work or missions before SHIELD. They didn't talk about the future or when they'd go back. It was fragile, but it worked. It was easy to live in those margins, in the present, in their life as they shared it starting in India just a few years ago. They had ample things to talk about—science, the Avengers, their enemies, even politics and the state of the world at large.

It was easy. Just talking, training, thinking and studying. No pretending, no lying, no fighting. Laughing together in the warm glow of the fire, swimming in the ocean and marveling at bioluminescent phytoplankton together—Bruce told her all about them and Natasha splashed him with water and called him a dork. Sparring on the sand under the hot tropical sun, Nat taking Bruce down over and over again, then running out into the water to cool down afterwards. Bruce trying—and failing—to identify constellations, eventually just naming his own, much to Nat's chagrin as she tried to teach him to navigate by the stars. Easy.