The next few weeks for Steve flew by.

Especially in chemistry, he and Stark and Bruce were all becoming better friends by the minute, even by just adopting Steve into labs that were only designed for two people.

Every time there was a lab they were supposed to be working on, Steve would put on his protective goggles like he knew what he was doing and set off to work, eventually messing up the entire lab and forcing a do-over. Tony never quite really got mad at Steve for that, though. He more just gave him an extremely affectionate look, a pat on the back, and it even looked like Tony longed to kiss Steve on the cheek. But maybe Steve was just hallucinating.

"Move over, 'captain'," Tony would say mockingly. He was trying to make a point that, even if he wanted to be in charge, Steve only knew how to be in charge of people, and not how to be a chemistry genius.

In Steve's, Clint's and Natasha's gym class, it was still the same thing. Steve would pretend like he knew what he was doing when it came to flag football or basketball or even capture the flag, but he would end up tripping, or completely missing the basket, or throwing the ball to empty air.

"Nice going, Captain!" Clint would shout, mocking Steve's US Military training. Steve kept having this feeling that Tony and Clint must meet up and tell each other about his chronic problem of messing up in what he doesn't know what he's doing.

But, now that Steve had been a student at this school for more than a month, it finally felt like things were falling into place, particularly when he started a big extra credit project with Bruce and Tony.

"Hey, Cap!" Tony shouted Steve's new nickname down the hall just before chemistry.

"What's going on, Tony?"

"Bruce and I have this great idea. We don't really need it, but the teacher is offering extra credit to people who develop, and perform, their own experiment. We-"

"We're thinking of using the lab equipment at Tony's dad's mansion," Bruce cut him off. "I'm going to be the coordinator of the experiment, Cap, so this time it's me that gets to give the commands."

"Tony's dad has a mansion?" Steve asked, confused and in awe.

"Yeah," Tony responded, gleaming with pride. "It's mostly different lab areas."

"The one I'm looking at in particular," Bruce continued, "is pretty close to both physics and medical science. For a while now, I've wanted to see the impact of Gamma radiation on living organisms. Because, I mean, we use X-Rays on people to get a good look on bones, and UV radiation to dry nails faster, and everything else, so why not Gamma?"

"Uh," interjected Tony, "because it's fucking dangerous?"

"That's just what we think," responded Bruce as they walked into the classroom. "But if we try it out on a few of Mr. Stark's leftover lab rats-quite literally, rats he hasn't used in experiments yet-just to see what happens, what could go wrong?"

"Haven't you guys thought that maybe it could affect us?" Steve asked. "I mean, if this thing goes horribly wrong..."

"Do you doubt the strength of the safe-rooms in Stark Industries?" Tony asked, pretending to be insulted. "My dad has these rooms with radiation exactly like Gamma for specific reasons, so he's had them radiation-proof, shatter-proof, basically break-in proof. It's like military-grade steel turned glass. Pretty cool stuff."

"That's why I think we should start working on it tonight," Bruce said, and Tony gave him a look of exasperation. "What? It's a Friday night, I know for a fact that none of us have anything going on," Tony was still giving him the look, "yes, even you, Mr. Perfect. We have the entire weekend to observe results, and the lab, whatever we try, is due on Monday."

"But-but-" Tony was so frustrated it was almost comical.

Steve tried to stifle a laugh. "It sounds like a plan. I'll drive Bells over later, around 5-ish, and I'll bring food. Then we can start."

After that, the day couldn't go fast enough. Steve, for some reason, couldn't help but be excited about working in the same room as Tony Stark. After all, Tony was the kid that decided to say "hi" to Steve on his first day of school just for the hell of it, the kid that was kind enough to try to help him in chemistry the first day. And now he and Bruce Banner and Tony Stark were spending an entire weekend together. Granted, they were going to be studying something Steve found totally unnecessary and hard to get a grasp on, but it was Banner and Stark. Nothing could possibly ruin this weekend.

Finally, the end of the day rolled around. Steve sped home on Bells. He emptied his backpack of everything but chemistry books and the necessary rations: cans of coke, chips, popcorn... He was set.

But nothing could have prepared him for when he pulled up to the Stark Mansion.

The hedges look professionally trimmed, the gravel driveway perfectly evened. Steve would place bets on hired help, but, knowing the Starks, it was probably the work of robotics. Despite how old the building probably was, the bricks and windows appeared to gleam, making the mansion look like a modern palace.

Just then, Tony and Bruce came out of the front door.

"Where are your cars? I thought I was the only one here," Steve said, hopping off his bike and taking off his aviators.

"Around the back," Tony replied.

"Apparently they don't like flaunting the fact that they have guests," Bruce joked.

"I'm gonna just," Steve started dragging the motorcycle across the drive, "keep my baby here. That ok?"

Tony shrugged, coming over to help move the bike. "I guess, yeah. It'll make a nice lawn ornament."

Steve punched Tony in the arm. Hard. "That's my pride and joy you're talking about, Stark."

Tony flinched back, rubbing his arm. "So you like it rough then, Captain?" he muttered to himself, a clever smirk making its way across his face. He came up behind Steve, and muttered a somewhat seductive, "I was kidding," inches away from his ear. He steadied his legs, ready to tackle the captain to the ground.

"Easy girls," Bruce said, pushing them apart, "Steve, Tony was joking. Tony, Steve didn't mean to hit you that hard." The scientist-at-heart rolled his eyes. It felt more like he was on babysitting duty and less like he was about to perform a highly dangerous experiment with two friends. "Now, let's go. We still need to set up the final parts of the experiment."

Before he turned for the door, Tony winked at Steve. "We'll settle this later," he mouthed.

Steve swallowed hard, feeling the awkward moment form in a sweat that dripped down his back. Once he recollected his thoughts, he followed a bit of a ways back, Bruce and Tony leading him from the majestic foyer to a chamber of stairs. Down the stairs, they weaved through a maze of high-tech, modern-looking labs. The group passed a few labs littered with excess parts of robotics projects before they finally came to their lab.

The main room, where the radiation was going to be, was a large room surrounded by the "military-grade steel" glass. There was a single, chrome metal lab table in the middle, a huge ray mechanism pointed at it from across the room.

"That," Bruce pointed, "is where the gamma is going to come out of. The rats are going to be on the table."

"I hope they explode," Tony said, rubbing his hands together, bouncing up and down like an over-excited school girl. The smile on his face disturbed both of his friends.

"Let's hope not," Steve muttered through his teeth, giving Tony a concerned look.

"Why, Captain? Afraid of a little blood and guts?" Tony asked, smirking at Steve.

"Not sure that you'd call an exploded rat just blood and gore."

"Are you seriously going to sit here and talk about what does and doesn't constitute as blood and guts," Bruce asked, getting annoyed, "or can we actually do this?"

"Well..." Tony smirked, batting his eyelashes at Bruce in a "you know you love me" sort of way.

Bruce rolled his eyes. "OK. You know what? Both of you go into the control safe-room, before you break something, or before I kill you."

He opened the door, shoving both Steve and Tony in the control room. "You two stay put. I'm gonna go get the... erm, the specimens, and bring them into the radiation room." He eyed both of them like they were children about to cause chaos. "Don't do anything stupid. I mean you, Stark."

Tony mocked a salute. "Yes, sir."

Bruce rolled his eyes at the cocky smile on the goateed physicist's face and slammed the door shut.

"So," Steve asked, throwing himself into the spinning desk chair and rolling to the end of the control panel, "what exactly are we doing?"

Tony grabbed the backrest of Steve's chair and maneuvered the chair and the soldier to the center of the panel, where they could overlook the entire lab room through a single pane of glass.

"That question," Tony said in a hushed voice, close to Steve's ear, "isn't the most important one to be asking right now."

Steve stood up in shock from the sudden move Tony had pulled. His legs pushed the chair out from between them,and he whirled to stand at Tony's eye level. If looks could kill, Tony was sure that Steve could have axe-murdered him then and there. The chair had pushed the two apart, though, and Tony was hardly whispering distance from Steve now.

Steve started to respond to Tony's flirtation, but he was still shocked and flustered from the interaction. "I-" He started, but he heard a click of the door to the lab room. The blonde watched as Bruce walked through the encaed lab and to the table, putting the cage of rats on it. It was clear that he was completely oblivious to Steve and Tony in the control room.

When Steve turned his head back around, Tony was nearly on top of him, pinning him against the control panel. He could feel Tony's breath on his neck as Tony muttered, "I'm sure that Banner's experiment is not as thrilling as you had hoped. Maybe," he let out a long sigh, tickling the hairs on the back of Steve's neck, "maybe we should put on an experiment of our own, Captain."

"Uh," Steve stuttered, his eyes darting from side to side, trying to find a way out of this situation, "I-"

Tony grinned at the flustered Rogers below him, and slid his hand onto Steve's thigh.

"Tony!" Steve gasped, stumbling backwards, balancing himself by hitting the control panel with both hands.

Suddenly, the little red lights all over the control room turned on, rotating to alert the experimenters of a change in plans.

"Oh, god-" Steve turned around and Tony rushed to his side to see what changes the control panel had initiated.

It read: COMMENCING RADIATION.

"Oh, shit!" Tony shouted, the seductive voice he had been using earlier completely gone and replaced with a sense of sheer terror.

"Bruce is still in there," Steve hollered, "we have to get him out!"

Steve and Tony ran out to the entrance to the lab room, Tony shoving his key into the lock.

"Damnit!" Tony pounded his fist on the door. "It seals when the experiment begins, we can't get in there!" His pounding became futile, as the young man slumped to the ground and began to sob. "Bruce is in there… it's all my fault… Rogers…"

"Get back," Steve commanded, grabbing the nearest fire extinguisher. When Tony refused to move, Steve gently nudged his companion out of the way. He started wailing on the door with the fire extinguisher, over and over again.

"It's no use," Tony sobbed, his voice hitching with uneven breaths. He and Steve both stared helplessly into the room, only to see Bruce's horrified face. Out of anger for his helplessness, Steve slammed the extinguisher against the door one more time. The wake of the force of the super soldier's impact ruptured a pipe, releasing a cloudy gas into the entire lab room. It was almost impossible to see anything.

"Come on," Steve spoke with his soldier-like initiative, picking up Tony and shoving him over his strong shoulder. The two ran into the control room,where Steve placed Tony down in the rolling chair and strolled him to the control panel.

"How do we shut it off?" Steve asked, panicked.

"How should I know?" Tony shouted back, a desperation rising in his voice that Steve had never heard before.

"This is your dad's mansion, isn't it?"

"That is irrelevant," Tony snapped back, scanning the panel in a fury, "Bruce set the entire thing up. All I could think about was... Never mind, that's not important. We need to figure this thing out."

Tony pressed the red button that had started this entire thing in the first place, to no avail.

THE RADIATION HAS ALREADY BEGUN, the computer's voice responded. So, Tony kept flipping various switches. "There has to be something, there just has to be- damnit! Where the hell is it?"

"Where is what?" Steve asked. He sucked with technology, so he felt helpless just standing there.

"There's always a cancellation switch. Some sort of way to end something just in case of emergency. A button underneath a case, perhaps, so that it doesn't accidentally get pressed."

"I would have expected the radiation button to have been under a case, too. My guess is there isn't one for a stop button if there wasn't a case for a start button on a radioactive experiment," Steve replied. "We gotta find a solution. Stark, our friend is in there."

"You think I don't know that?" Tony turned to face Steve quickly, and Steve could see tears welling up in his eyes yet again. "Fuck it," he stormed out of the room in a panicked anger, and grabbed the fire extinguisher.

"Tony, what are you-" Steve tried to stop him, but Tony let loose with the extinguisher, ramming it into the control panel. After a few final beeps, the control panel lights blinked back to green, and the now shattered screen read: STAND BY.

"Good," Steve gasped. It felt like he had been holding his breath the whole time, despite having a cool facade.

But he spoke too soon.

Just as the final beeps stopped, a large thud sounded from the clouded lab room.