Bruce refused to accept the plan for a long time.
"You're all mad," he insisted, "handing over immense cosmic power to the Big Guy? It's like you all have a death wish!"
Mulder couldn't help but think he had a point. He had yet to meet the Hulk in person, as it were, but he'd watched enough footage of the Avengers during Code Green action to worry about the sanity behind intentionally infecting him with an ancient, malevolent entity of infinite power. Even Scully admitted that she had no idea if the vaccine the lab was now racing to develop, based on the antibodies she had identified, would even work on the Hulk. A test of Bruce's blood had revealed entirely standard, if heavily gamma-infused, antibodies, but no one was foolhardy enough to try and take a blood sample from the Hulk to see if those differed in any way.
Worse, Scully, Tony, and the other lab techs had all agreed that vaccinating Bruce before they attempted their plan was a bad idea because the Purity virus might not be able to take hold and would then target one of the others, meaning someone would have to try and give the Hulk the shot while he was superpowered. To add complications, another team of lab techs were now hard at work developing a syringe capable of piercing the Hulk's skin - something nobody felt confident about.
All that paled in comparison to their deepest fear however, what would happen if the vaccine didn't work? There was no question about allowing a Purity-infused Hulk loose into the world and that left only one solution. If they couldn't control or contain him, they would be forced to kill him. Bruce accepted the risk - he'd always felt that a scenario like that would inevitably have to play out one day - but the others fought against it until Bruce appeared in the Avengers lounge one night with a piece of paper.
"This is a contract," he told them, "I had my lawyer draw it up."
"You have a lawyer?" Tony interrupted, "do I know him? You know I roll with all of New York City's elite."
"I doubt it. His name's Murdock. Quiet guy, blind, lives in Hell's Kitchen, and works with a lot of small-time powered people. Anyway, we're getting off-topic." He placed the contract down on a table and all the Avengers moved closer to take a look.
"I'll summarise. It says that I will only consent to intentional infection by the Purity virus if every one of the Avengers agrees to kill me if the vaccine doesn't work and all reasonable methods of control and containment fail."
There was a cacophony as all the other Avengers at once began arguing but Bruce held up one hand to silence them.
"Those are my terms. Take it or leave it."
One by one, the Avengers conceded and signed their names at the bottom of the sheet. Mulder watched Scully sign hers and hand it to Natasha who had refused until the very end.
"Bruce.." she began but he held up the hand again.
"You can't convince me."
"You need to sign it Nat," Scully said quietly, "we have to do this."
"I know. I just…" Nat looked over at Bruce and Mulder could have sworn she had tears in her eyes. He watched as she slammed the paper down, scribbled her name at the bottom, and stormed from the room, Bruce following.
"Leave them," Scully told Steve who had got up to follow, "they need to work this out alone."
After that night, Thor returned to Asgard in the hopes of locating a relic capable of containing the Aether, or at least, the fragment of it that had been trapped on Earth in the form of the Purity virus. Steve had the team running endless training drills and it was after one of those that Mulder and Scully had walked slowly back to their shared quarters feeling battered and bruised. Steve had pitched the group against a simulated Hulk and Scully had found herself picked up and thrown against a wall twice within the space of half an hour. She was convinced she had at least three broken ribs to show for it. Only Bruce had shown her any real sympathy, although Scully had noted that he seemed more focused on Natasha, who showed up at their door half an hour later bearing pizzas.
Collapsing onto her bed, Scully groaned.
"At times like this I wish I could heal myself as fast as I can heal other people," she muttered. Mulder snorted a laugh as he grabbed his own pizza. He devoured a whole slice in a matter of seconds and sighed.
"God I needed that. Though it would have gone better with a cold beer."
"Ugh, don't," Scully said between bites of her own slice, "I'd kill for a beer right now."
Steve had banned the entire team from drinking until the Purity situation was resolved and they were all stuck aboard the helicarrier, leaving them limited options for blowing off steam.
"I feel like I did the first day I ever trained with you Nat," Scully muttered, rubbing at a large bruise on her arm.
"I bet that took some building up to," Mulder replied from around a slice of pepperoni.
"If you call day one on the job a build-up then sure."
Mulder looked over at her.
"They had you train with Natasha on your first day?!"
Natasha laughed and rolled over from her spot beside Scully to tell him the story.
Natasha Romanov stood, feet planted firmly shoulder-width apart and arms folded across her chest, staring down at Director Fury. It was a stance designed to intimidate and it probably would have worked had it been aimed at a lesser man. Fury however simply gazed back at her without a hint of discomfort.
"When I agreed to join S.H.I.E.L.D. I didn't sign up for babysitting duty," she growled.
Fury resisted the urge to roll his one remaining good eye.
"Then consider it an exercise in team building."
Romanov gave in to the urge Fury had resisted and he smirked. "She's new, she's confused, and she could use a friend."
"And you think of me? You recall I don't have the best history when it comes to making and retaining friends?"
"Trust me. I have my reasons." He picked up the manilla folder on the desk and flicked it across to her. She caught it without flinching. "Just read the damn file."
…
One hour later Romanov stood outside a grey door cursing Fury's name under her breath. One of these days he was going to be wrong about something and on that day she was going to be there to gloat.
The door opened and she found herself facing what could have been her own reflection. The short redhead looked slightly bemused to find someone at her door. She was dressed in sweatpants and an athletic shirt and clearly had not been expecting company.
"Fury sent me. He figured you could use a friend and seemed to think we had enough in common that I'd qualify."
"I don't need a babysitter," the redhead replied. Romanov smirked a little.
"And I didn't sign up to be one." She looked at the other woman's outfit. "Were you working out?"
"Yeah, there's only so many hours I can sit reading reports. I think my muscles were beginning to atrophy."
"Has anyone shown you the gym?"
"No."
"It's got a few special features, wanna take a walk?"
"Sure." Scully eyed Nat up and down." It's Natasha, right? Romanov. The Black Widow."
"Right. You prefer Dana or Miracle?"
Scully answered with a snort.
"Dana, I'm still not used to having a code name."
Scully grabbed a hoodie and followed Natasha down three levels to a door marked "Training." When they walked inside they were met by a very large, very empty room.
"I was expecting something a bit more impressive," Scully deadpanned.
"I'm sure I can figure out how to wow you. Watch this, and make sure you stay behind the orange line."
Scully shuffled her feet back so she was well behind the line painted on the floor and watched Natasha cross to a panel on the wall.
"Access Romanov, simulation twelve."
As soon as she finished speaking, the room began to change. Panels shifted on the walls forming into blocks and benches. Ropes dropped from the ceiling creating meshes, nets, and impossible looking bridges. Within a minute the empty room had transformed into an assault course.
"The room is fully programmable," Natasha explained, "Stark designed it for the Avengers because everyone had such different requirements." She turned back to the panel. "Access Barton, simulation five." The room changed again. The blocks shifted positions and over 30 archery targets appeared, some moving, some static. "You can add hostiles too. Add hostiles, package beta." All around the room holographic shapes appeared, pacing along the edges of high blocks and crouching behind others. "They won't attack until you cross the line, at that point you're fair game."
"OK, I'm impressed."
Natasha gave her a fast grin then turned back to the panel.
"Clear hostiles, access S.H.I.E.L.D., simulation ten-thirteen."
The room shifted again, clearing of nearly everything except a few well-placed blocks.
"Want to go one on one? If you've been stuck reading in that tiny closet they call quarters you could probably use some fun. I'll go easy on you"
One corner of Scully's mouth raised into an amused smirk.
"Don't."
Natasha smirked back.
"OK, you asked for it."
The two women walked to the center of the room and faced off. After agreeing on a few basic limits, they began to spar, and within seconds Natasha found herself on her back staring up at the ceiling. Despite her agreement, she had held back out of curiosity, wondering what this new recruit could do. Now, she understood, she might finally have a sparring partner worth her time.
She righted herself almost immediately and unleashed a couple of favorite moves that the new girl, unlike nearly everyone else on board, wouldn't know yet. This time, it was Scully who found herself on her back, suddenly staring at the ceiling. She too righted herself quickly and was ready to go again. The pair spent nearly an hour learning one another's moves, testing limits and challenging weaknesses they found in their opponent's defense. By the time they were done, they were both tired, aching, and thirsty. Natasha led Scully down to the nearest mess room and they sat at a long, empty table drinking ice water. Neither of them said much, but by the time they split ways to head for their own quarters and a couple of long, hot showers, both felt as if they had maybe found someone aboard the often lonely craft whose company they might enjoy more than most.
"And that was that," Nat finished. "Within a year we were working together so well together that we requested shared quarters so we could talk late in private. That got a few tongues wagging. Mostly Tony's."
Scully laughed, a proper full laugh that Mulder hadn't heard in far too long and it filled him with such joy that for once, he found himself able to fully relax.
Several hours later, Mulder awoke to the sound of multiple alarms. Coming to his senses, he realized he was hearing his own personal alarm as well as those of Scully and Nat who had fallen asleep together on Scully's bed surrounded by a mess of blankets and empty pizza boxes. As the two women also woke up and checked their own phones, Mulder read his. It was an urgent message from Steve.
"Thor is back. Avengers Lounge. Now."
Thor was standing in the middle of the Avengers Lounge with Steve, Tony, and Bruce when Mulder, Scully, and Nat arrived. Steve immediately handed Scully a cuboid-shaped object. It looked like a box carved from solid rock with gold inlaid along the edges and corners. She turned it over in her hands for a moment before passing it to Mulder and raising an eyebrow at Thor.
"It is an ancient relic from the Asgardian vaults," he explained, "according to the experts I spoke with, it originated on Svartalfheim and was crafted from a form of rock found nowhere else among the Nine Realms." He reached out and took the object from Nat who had just finished examining it. Gripping either end, he pulled it and the object expanded, revealing a hidden chamber within. "The chamber is guarded by a powerful force field. Our historians did not know what it once contained, but they suspect it is likely to have been an object of immense power."
"Do you believe it can contain Purity?" Scully asked bluntly.
"I believe it is our only option."
She nodded at his answer.
"Then it will have to work."
The helicarrier lab worked through the night, pulling in their most brilliant scientists from around the globe to contribute ideas and general expertise to the vaccine development. Coulson was thrilled to welcome his old friends Fitz and Simmons aboard, the former to work on the Hulk-proof syringe while the latter threw herself immediately into synthesizing the antibodies Scully had identified. In the five-minute break she allowed herself to eat, Scully introduced Mulder to Dr. Helen Cho from the U-GIN Research Group who had also been brought aboard along with several senior members of her team. At 4 am SST (S.H.I.E.L.D. standard time - the measure by which all operations globally were carried out), Mulder was awoken by a message from Scully saying three simple words: "We did it."
One hour later, the team all stood in the main helicarrier lab, staring at a single vial of amber-colored liquid.
"You're sure this will work?" Steve asked. He was always the most cautious of the group when it came to relying on scientific and technological solutions, preferring a straight fight whenever it was an option.
"As sure as we can be," Scully told him. "We created this directly from the antibodies I showed you, we stripped the antibodies from an existing vaccine and replaced them with these. It's our best bet."
"But you're not certain?"
"We can't be without testing it. Deliberately infecting someone here with Purity and trying it out on them."
"Then do that."
"We can't, we're out of time. Today is December 22nd. We have to stop it today or lives will be lost."
"Besides," Bruce added, "even if we had the time to conduct full clinical trials, there's no guarantee this will work on the Hulk anyway."
"Are you happy about this?" Steve asked him directly.
"Well, not really no," Bruce answered, removing his glasses to rub his eyes, "but I trust everyone who worked on it and I believe them when they say it's safe and likely to work." He replaced his glasses and looked Steve in the eyes. "I'm ready to do this."
Steve narrowed his eyes for a brief moment then gave one curt nod to Bruce and turned back to Scully.
"Do we have a location yet?"
"Coulson, Fury and I have been working on that," Mulder cut in. "We want it to thaw out slowly, to give us the best chance of stopping the process if it looks like something is going wrong."
"So somewhere both cold and unpopulated?"
"Yes." Mulder turned to Scully and shot her an apologetic look. "Looks like we're going back to Antarctica."