Once they'd hit cruising altitude and top speed—Mach 2.1, nice—Duo engaged the autopilot. He gave himself a minute to just enjoy the view. At 65,000 feet, the curve of the Earth was readily visible, and it made him a little nostalgic. It had been way too long since he'd been back to space. His minute up, he turned to Hill. "Sweet ride you've got here," he said. She gave him flicker of a smile.

"Your father did design it," she gave credit where it was due.

"Might have to pick his brain then. Ship like this"—he petted the dash—"that can get around this fast could definitely be useful."

"If this works out, you might be able to do just that," she said. She glanced at him. "How do you know Miss Noventa?" she asked, and he could practically feel everyone in the back perk up to listen in. "She didn't tell me she knew you."

"Is there some history there?" Stark asked. "Neither of you seemed exactly what you would call happy to see each other."

Duo sighed. "It's… just old shit. She was a friend of… my ex." It hurt to say that, no matter how true it was. "That's all."

"And… you had a problem with that?" Stark asked, but his tone said he'd be surprised if he did.

Duo let his eyes roam over the instrumentation, mentally validating that all the readings were actually in the green, not just green because the systems showed they were. "It's not… personal. They had a history. I didn't think being friends with her was healthy, but I was overruled. She's never been anything but polite to me, and it's all a moot point since he doesn't remember either of us now," he said, rushing to get it all out because it was not a topic he wanted to dwell on. "Do you have this?" he asked Hill.

"I've got it," she assured.

"Thanks." He stood and went back to where the others were buckled in. Even at Mach 2, once they were no longer accelerating, the G forces evened out, so it didn't feel very different than normal flying. "So, how much do any of you know about mobile suits?" he asked, sitting in a side seat.

Vision began to rattle off what sounded like the Wikipedia article, and Duo put his hand up to stop it. "Okay, so, nothing." That was just… great. "We're lucky, it looks like we're dealing with manned machines and not Dolls."

"Dolls?" Rogers asked.

"Unmanned mobile suits," Vision volunteered, looking like he must be researching. There wasn't a lot of information about them out there—quite purposefully. No one sane wanted Mobile Dolls to exist. "Anecdotal evidence suggests they were superior in combat even compared to OZ's Specials corps."

Duo wasn't getting into it—they wouldn't have been programmed to deal with human-sized threats anyway. There was a good chance the Avengers would be able to deal with them before the algorithms could assimilate the data, but to his knowledge, Mobile Dolls had never been used in atmo, and they wouldn't be used for something delicate and noncombat related.

"Why on Earth—?" Rogers looked horrified.

Right—tactical genius, and actual war vet. He'd understand the larger implications of Mobile Dolls a lot faster than a civilian would.

"Off topic," Duo dismissed. "The point is, we're dealing with people in suits, not Dolls, so that's an advantage. Even the best mobile suit pilots aren't trained to deal with human-sized targets. Your speed and your agility are going to be the biggest assets outside of sheer firepower. I cannot stress this enough—keep moving. These are Leos, so they don't have any flight capability. They're highly maneuverable and adaptable, but almost all of the visual cameras are housed in the head." Stark helpfully used his phone to throw up some images. "You kill the head, it should be pretty much dead in the water unless someone panics and starts shooting blindly."

"That seems like a terrible design flaw," Rogers said.

Shrugging, Duo sat back in his seat a little. "Putting cameras on the chest forces your visibility to depend on where the chest of the suit is facing. The head can allow pilots to get better range—most suits have at least a 180-degree field of vision off those cameras. I know you're all pretty much used to hitting whatever you aim at, but for average soldiers and pilots, a headshot is a difficult shot. Outside of the cockpit housing, that head is the most reinforced part of the suit specifically because its cameras and sensors are so important, which means taking it out is actually really difficult."

Tony was listening—of course he was, it was important information to have—but part of his brain was reeling. This wasn't theoretical knowledge; it wasn't something learned from a book or a training course. A terrible suspicion formed, but it just couldn't be, right? Duo was fifteen during the First Eve War—maybe not even that old. But the last time mobile suits were widely used was in the Second Eve War, when Duo was sixteen. His brain calculated his age because it couldn't not. Duo himself admitted that Preventers didn't even have mobile suit forces on Earth anymore. They had fallen out of style after the Eve Wars, and Tony never thought about why before. But if not during the Eve Wars, when could Duo have gained this level of expertise?

Duo talked about mobile suits in depth. He answered any questions that any of the team threw at him with confidence that only came from intimate knowledge. He knew these weapons, knew how to deal with them as a single operative, and yet he armed himself with knives and guns. If someone were only listening to Duo talk through the assignment and couldn't see him, they'd assume he was an experienced veteran.

It had been over two years since Duo last worked a standard Preventers assignment, but he fell into the mindset as easily as breathing. For the first time, Tony wondered if maybe Une had been right to deploy Duo the way she had in the past.

"Duo will not tell you a lie… Don't think that means he's being honest. And don't make the mistake of thinking that just because he won't tell you the lie, that he isn't perfectly content to let you believe one."

"Everything I've told you is pretty much common knowledge in Preventers."

"…Perfectly content to let you believe one."

Waving a hand to make a point, Tony caught sight of the scars on his palm.

Duo was younger then than Peter was now.

"Is… there something we should be aware of?" Bruce asked—probably the most tactful Avenger in the club.

Duo hesitated before he answered. "My immune system is weird."

Tony made himself keep breathing steadily. He didn't say he wasn't enhanced.

"Tony," Cap's voice was sharp, like he'd called Tony's name more than once, and it made Tony look at him. He may have sounded sharp, but he looked concerned.

"I was listening," he said, replaying the last thing Duo had said. "Taking them down like ATATs in Star Wars probably won't work."

Cap gave him another thoughtful look. "You've just been… quiet," he observed. It was carefully nonjudgmental, and that was a little new, but Tony ignored it.

A small smile quirked at the side of Duo's mouth, but wheels spun behind his eyes. He stood up and stretched, and Tony realized they were more than halfway to their destination.

"You've got the main points now," he said. "Anything else… we're just going to have to see what's there when we get there. I hear that's something you all tend to specialize in." He began to move back to the cockpit.

Peter jumped up. "Mr.—uh, Darkside, sir?" he asked.

When he turned to look at Peter, who fidgeted in a way that Tony did not find at all endearing, his smile was sincere. "Duo's fine, or just Darkside. None of this mister crap. What's up?"

"Do you mind, um, that is… can I? I mean, I'd like—"

"Spit it out, kid."

"Do you mind showing me how to fly this?" Peter blurted. "The Quinjet, I mean."

Surprise flashed across Duo's face, but he shrugged. "Sure."

"I was fighting a war when I was younger than he is."

"It's just… strange, though, isn't it? It seems like Maxwell has some really high connections. It feels off."

"Duo." Tony jumped when he heard his own voice say it, because he didn't mean to.

Duo paused and turned back to him, expression expectant.

How did you learn all this? The question caught in Tony's throat. Just seeing Duo framed in the light from the windshield on the jet next to Peter who stood at least three inches taller than him, he seemed small and fragile. It seemed impossible to even think of when he was younger and smaller.

"Did you need something?" Duo asked.

Tony coughed to clear his throat because that barely-formed hypothesis was absurd. "Would you go with me to the MET Gala?" he asked, his thoughts finding the only excuse they could.

Tilting his head, Duo asked, "The MET Gala?"

"Yeah," Tony said. "Big, fancy, schmancy event they hold every year. I've got an invitation and a plus-one, and Pepper tells me that we need to do an official introduction of you at some point, so, if you wanted to, uh, kind of do the public thing but still hide, we can probably doll you up so you're not really recognizable," he finished, feeling lame.

When Duo didn't reject it out of hand, the band around his chest loosened. "Whatever. It's not the worst idea I've heard," he admitted. "I'm not crazy about big shindigs like that, but it sounds like it should get the job done."

"Is that a yes?" Tony asked.

Duo shrugged. "Yeah, barring work."

"Okay, good," Tony said, and if Duo gave him a look like he was behaving weird, he brushed it aside.

At his side, Cap said, "The MET Gala?"

"What about it?" Tony asked, defenses rising automatically.

"I didn't realize you were going," Cap said.

Tony blinked at him, feeling stupid. "You are?" he asked, because, now that he thought about it, Cap getting an invitation made sense—literal American icon and all, recent mishaps notwithstanding—but Tony was used to being the only Avenger with enough public currency to get an invite.

"Yeah. I wasn't sure if I should go." His face was open and honest, and he met Tony's eyes like he used to before—like they were on the same page, the same team. It had been a long time since Steve had looked at him like that.

There was a part of Tony that was still hurt and wanted to be mean for the sake of being mean. It wasn't fair of Steve to look at him like that after everything. Tony may have taken them back, but no one with a brain would have said they made up or resolved anything. Tony worked to get them back on the right side of the law and in the right country because it was the right thing to do—for everyone. Especially with the fall of SHIELD, the world didn't need the added stress of seeing their heroes divided. He didn't do it because he'd forgiven Cap. He did it because he wanted to be the bigger man and look at the bigger picture.

For those reasons, he bit back a dozen pithy, petty, mean-spirited comments that jumped to mind and instead said what he might have said before. "You don't like being on display, and you won't get much opportunity to enjoy the art if you go."

Steve was still watching him with those too-blue eyes, just watching, waiting patiently. When was the last time Steve hadn't jumped down his throat for holding something back? "But?" he finally prodded. Still patient. Still waiting.

Tony opened his mouth to answer, kind of squawked, quickly covered it by clearing his throat, then said, "But if you were asking Pepper, she'd say that having us present a united front to the world when, particularly when introducing Duo to it, could only be a good thing," he forced out, the words almost tumbling over each other in their rush to spill out, be done, have this conversation over with.

The gears turned behind Steve's eyes, his genius real but so much more subtle than Tony's that people often missed it. "If I come and we avoid each other all night…" he said.

"That'd be bad," Tony supplied because he was done. He didn't know how to deal with a Steve that wasn't antagonizing him, wasn't saying "white" just because Tony said "black." It felt like back when they were a team, maybe even a family, and sure, they'd always had their disagreements, but Tony thought that family had been shattered beyond repair. He didn't know how to deal with a Steve that seemed to be offering it again.

And if Steve kept looking at him with those too-sincere eyes, Tony was going to get angry. Because Steve was acting like everything was fixed, and it wasn't, and for once in his life, Tony wasn't the one who broke it. He'd already made all the overtures he was going to. He'd done way more than anyone could reasonably have asked him to. He had his parents' murderer in his home and was trying to help the guy. Tony was done making the overtures. The next move was in Cap's hands, and Tony would be damned if let Cap off the hook for this one.

Their weird tension was interrupted by a fast, techno-y sounding ringtone with… was that Chipmunks singing?

Duo, of course Duo, picked up the phone. "I'm kind of about to be busy. Can it wait?" he asked without greeting. He listened for a moment, and then he went very still. "It wouldn't happen to be in Zhangjiajie National Park, would it?" he asked in the kind of tone that suggested he knew the answer. Tony thought they all jumped when Duo slammed a fist up against the roof of the Quinjet. "Motherfucker. We are going to have a very long talk about the appropriate disposal of WMDs when we get through this. Where is it—exactly? And I need to you to give me a complete rundown on how to crack the security on it." He paused then said with genuine anger, "Because we're still more than forty-five minutes out, so at best I'm going to have fifteen to crack it. I don't have time to brute force it, even if you are using our code." He paused again, then dissolved into something that sounded like a Chinese language, but Tony wasn't sure which one.

"He did say WMD, right?" Wilson asked while Duo continued to alternate between cursing and berating whoever was on the phone. "Like, weapon of mass destruction, WMD?"

"I don't know any other meaning for that acronym," Cap said, face gone tight.

Tony waved Peter back to his seat and got up to go talk to him. Duo had gone quiet, though he was strung so tight, he was all but vibrating as he listened to the person on the other end. Tony could only make out that the other person wasn't speaking English, so he probably wasn't going to have luck overhearing.

Duo's eyes jumped to him, he said something that must have been some form of "hold on" to the person on the phone—Chang, maybe? Tony thought the ringtone sounded like a Chipmunk version of the ringtone Duo had used for Chang previously. "Unless you can light up the afterburners on this baby and give us some more mphs, I'm busy."

The cold tone reminded Tony of Duo standing with his foot on a Hydra agent's neck. "Stop begging. It's embarrassing." Tony told himself he'd faced down bad guys way scarier than his son. "We need to talk about this."

"We will. Right now, I need to listen to this."

"A weapon of mass destruction?" Tony pushed, even though Duo's eyes grew colder with every word he said.

"It's a nuke," Duo said, blunt, and starting to sound more than merely cold; he was starting to sound angry. Something told Tony he didn't want to see his son angry.

"A nuke?" he asked. "Shouldn't I be in on this disarming conversation then?"

"Can you learn L5's dialect well enough to engage with the protections on it?" Duo demanded. Tony opened his mouth, but—and it really was depressing how often Duo had that effect—nothing came out. "I didn't think so. So unless you can speed up the jet, go sit the fuck down and let me learn what I need to so we can avoid nuking a national park. Sound like a plan?"

Thoroughly dismissing Tony, he turned his attention back to the phone and said something else in what must be L5's dialect.

Hill turned to him. "Can you make the Quinjet go faster?" she asked seriously. It sounded like Duo had moved from merely listening to asking questions, his full attention on the person on the other end of the line.

"Yeah," he said, because he did have a number of modifications for the Quinjet he'd held back—at least two of them could be implemented through existing systems. He pulled out his phone and plugged it into the dash. Duo's eyes flicked to what he was doing, then his attention went back to the person on the phone.

Tony wanted to push, but Duo wasn't going to give them anything till he was good and ready to. Fifteen minutes to disarm a nuke at their current pace—probably less by the time they got through the mobile suits and into wherever it was kept. "Give me the power routes, FRI," he said, and FRIDAY projected them for him to see.

Tony needed to give them more time than that.