In Our Defence

A/N: So, I got this prompt from Loki Firefox and ran with it. Note that all my work is unbeta'd, so any faults are my own. And I'd really like to thank every for all the reviews, follows, etc, as well as a special thanks to Loki for the prompt which inspired this story.

"Do you really think it's wise we leave those two here on their own during this mission?" Natasha asked, her gaze lingering on Blaine and Sebastian who were both giggling manically as they tinkered with their latest invention.

"I think they'll be fine," Tony scoffed, continuing his packing and not even glancing towards his son.

"Tony," she sighed softly in exasperation. "Last time we left them without someone watching them, they blew up Stark Manor and unleashed a minor mushroom cloud from an array."

"So?" Tony zipped up his bag. "That was last year, no one got hurt, so no harm, no foul."

Natasha starred at him incredulously. "No harm, no foul?" she wondered out loud. "What about the time they dyed Steve, Hawk, and Thor blue? Or the kid they sent to the hospital? Or how about – "

"Okay, I get it," he interrupted, throwing up his hands in defeat. "Look, I'll get them to promise to behave. How bad could it be? We're only going to be gone for two weeks. They're on spring break and should be back at Dalton, under supervision, before we even get back." He paused, thoughtfully, taking in her unconvinced look. "If you're that worried about it, have Fury send someone to check on them in a few days."

She sighed again, wondering once more how she got stuck babysitting the genius philanthropist who was no better than his twelve year old when it came to responsibility. A shrieked "Seb!" had her gaze flying back to the two at the table, where they were both looking sheepishly at the new hole in the wall between the kitchen and dining room, the drywall still smoldering and crackling from the heat.

"Hm, I think we set it too high," Sebastian stated, glancing down at the laser gun in his hands.

"Tweak it bud," Tony offered, moving forward to study the hole. "Although, this would make an awesome weapon. What were you boys planning to use it for?"

"We were trying to heat molecules in the air to make it easier to dry off from the pool," Blaine offered. "Instantaneous dry so Aunt Tasha would stop yelling at us for dragging water all through the house after we swim."

"O-k-a-y," Tony drew out the word, studying the wall again. "I can see what you mean about the setting being too high."

Natasha sighed again, holding out a hand for the laser. "Stop encouraging them," she snapped at Tony. "Give it to me boys."

"But Aunt Tasha," Sebastian whined, sticking out his lower lip in hopes of swaying her decision. "We were getting ready to perfect it."

"And you can," she answered, striding forward and pulling the weapon from the boy's grip. "When we get back. I don't want to have a repeat of last time we left you two on your own."

"But it was epic," Blaine protested. "The mansion all but collapsed on its self and we were blown like five feet when the array went. I didn't know Seb and I could get that kind of air."

She stared at her nephew in surprise. "I think you and Seb have been spending too much time together," she responded. "Whatever happened to the quiet Blaine Anthony Anderson Stark that use to exist? The boy who actually listened and tried to stay out of trouble?"

"He started spending time with me," Sebastian replied, puffing out his chest in pride.

"No kidding," Natasha muttered, wondering yet again how Bruce, the quiet scientist who tried to control his emotions, managed to spawn the little devil sitting at the table.

"Just promise you two will try to behave," Tony stated, heading towards the lab. Natasha started to follow him, apprehension evident in her reluctant steps.

"We promise," they replied in unison, grinning at each other as the adults embarked on their mission.

"Hey, Seb?"

"Yeah?"

"Did you hear that?" Blaine asked, glancing over at his friend sprawled across the other couch in the room, his gaze still fixed on the television. He could understand why his friend had insisted they buy this model when they had renovated the great room; the picture and quality were awesome.

"Hear what?" Sebastian glanced over at Blaine as he muted the TV.

They were quiet, each holding their breath, when the sound happened again. "Is it me or does it sound like someone is trying to break into the house?"

"To the lab," Sebastian responded, already bounding from the couch, television completely forgotten. Blaine was hot on his heels as they scrambled down the elevator to the underground lab.

"JARVIS, conduct a perimeter scan for unknown life forms," Blaine called to the super-computer as he and Sebastian entered the lab.

"At once, Master Blaine," the computer responded. "It would appear a small army is advancing on the mansion from the West and I have a squadron of men attempting to scale the building and enter through the second story."

Surprised, Sebastian and Blaine looked at each other. "Fury?" Blaine asked, wondering if the man from the government was checking up on them.

"I'd say not," Sebastian replied, rolling his eyes. "Someone who doesn't like our fathers and their friends probably figured we'd be the best targets while they're on a mission."

"To the Enterprise?" Blaine asked, suddenly grinning in delight at the prospect of testing out the secret room they had built when the mansion had been remodeled.

Sebastian grinned manically, and nodded enthusiastically. "To the Enterprise," he agreed, leading the way down the corridor and away from the lab. They entered a code into a hidden wall panel, and stepped through, grinning at the room beyond.

The Enterprise was their secret room, a replica of the star ship's bridge, complete with floor to ceiling view screens at the front of the room. They had come up with the concept after a brutal attack on the mansion while they were attending school. Figuring they would need a command post for defending the mansion, they had brain stormed and come up with the Enterprise, their ability to control the "defenses" they had secretly installed around the grounds which translated to their pranks for their uncles.

"JARVIS? Initiate protocol Enterprise Nine Sixer Omega," Sebastian called out to the computer, rubbing his hands together in anticipation. "We're going to show these guys what it means to mess with a Stark and a Banner," he informed Blaine, taking his place at the weapons consol as the super-computer brought on line their scenario. Around them, holographic images of the original cast of the show appeared at their posts, ready and waiting for instructions.

Blaine grinned, and took the Captain's chair, glancing over at Sebastian. "Man, we didn't do half-bad with this," he said.

Sebastian returned his grin. "Let's get this show on the road," he agreed.

"Mr. Solo, please bring up the mansion grounds on the view screen. I would like to see where our enemies are," Blaine called over to the hologram.

"Of course, Captain," the man agreed, fingers dancing across his computer keyboard. Instantly, the view screens were flooded with men attempting to scale the building and more moving in from the distance. Blaine frowned, eyes wide as he took in the troops attacking.

"Okay," he breathed, trying to figure the direction they should take. "Um, Mr. Spock." Sebastian looked at him with a grin, happy to have been named after his favorite character. "I would like you to clear the men scaling the building. They're the most immediate threat."

"With relish, Captain," Sebastian replied, fingers dancing over his own consol. He grinned as a large fire hose rose from the ground on the west side, held aloft by a mechanical arm. They had installed the hose after the fire that had demolished the mansion the day their array had been blown up after a failed experiment. He and Blaine had figured it would be in everyone's best interests to have a better fire prevention system rather than relying on the local fire department to arrive. With a dark grin, he opened up the fire spray, swinging the hose and knocking men from the building with the force of it. While not lethal, several of those falling from the second story weren't moving quickly to get up, the wind knocked out of them as they fell.

Once he had cleared the men, Sebastian retracted the fire hose, grinning at the mess of men and fire foam . He glanced up at the screen, studying it as he noted that the men he had cleared from the building appeared to be stuck in the grass. On closer inspection, one was even hanging upside down on the wall of the building. Sebastian glanced back at Blaine who had a satisfied smirk of his own.

"You didn't?" Sebastian laughed, giggling as the upside down man seemed to be screaming for help.

"I did," Blaine said, his own eyes wide in delight at the display. "You remember that sticky foam we created and tested on your dad?"

"You mean the one where we managed to get him to Hulk-out and stuck him in place when he ran after us in his fury?"

"Yup, and it held him for five hours, even when he morphed back into his human form. He was pretty mad that he lost a layer of skin on his feet from that. I may or may not have added it as an option when using the fire hoses."

"Blaine," Sebastian gasped, trying to hold in his laughter. "I think Aunt Tasha was right; you may be spending too much time with me."

"Hush," Blaine responded, eyes drawn back to the screens. He frowned, watching as more reinforcements arrived. They skirted around the mess the boys had made clearing the men from the wall. "We've got more company," he added, indicating for Sebastian's gaze to take in the new arrivals.

Sebastian's gaze took in the men trying to ram the door with a battering ram. "That's kind of archaic," he criticized, nose wrinkled in disgust. "What is this, the middle ages?" His fingers danced across his keyboard, allowing a large ten-foot deep trench to open between the front door running the length of the front of the house. Several of the men, fell in before they backed off to assess the new development.

"And your solution isn't?" Blaine scoffed, taking in the way the attackers were regrouping and trying to come up with a solution to their new problem.

"Hey, don't knock the classics if they work," Sebastian responded in an offended tone. "They're the ones that wanted to revert to medieval siege tactics. I'm only indulging them."

Their attention was once again diverted from the front door as a whirling sound echoed and reverberated through the house. Their gazes instinctively went upward before being drawn to the camera angle into the sky. "No way," Sebastian breathed, watching as three helicopters came towards the house. "They're bringing out the big guns."

Blaine hummed in thoughtful agreement, assessing the attack before grinning. "Hey Seb, remember our catapult we installed on the roof two summers ago and rebuilt after the mansion collapsed?"

"The one we used to lob flour bombs at approaching cars?"

"Yup," Blaine grinned. "It's still up there, and I know we didn't complete use our arsenal. Do you think Idiot 2.0 would be like to be tagged in as a soldier?"

"I like," Sebastian grinned, pulling up Idiot's controls and sending the mechanical arm to the roof of the mansion. Once the arm arrived, he grinned as he used it to retrieve the flour bombs from their cache and load the catapult, sending the first flour bomb flying towards the approaching helicopters. His shot fell short, but didn't deter the approaching troops. With a smirk, he send the next one, managing to hit one of the three choppers, sending it spiraling to the ground from the impact. A small explosion occurred as it connected, sending debris, flour, and dirt shooting into the air. "Hit!" he cowed triumphantly. "I got this," he called to Blaine as his eyes caught more men moving towards the house.

"Okay," Blaine agreed, having pulled up his own keyboard, intent on stopping the marching men. He clicked a few buttons and cowed with triumphant when the molasses lake they had installed opened. Sebastian looked over as Blaine laughed in glee.

"Is that the molasses lake we sunk Uncle Steve's porsch into?" he asked in delight. "I thought Dad and Uncle Tony took it out?"

Blaine grinned slyly. "I may have convinced Dad that taking it out would have great ecological impacts," Blaine responded, frowning as he saw someone lob a grenade through a window. "Dad just installed a trap door so Uncle Steve wouldn't drive into 'accidently' again." Sebastian grinned to himself, pleased that his lie about what had happened to the porsch had been believed by their parents. The room shook as the grenade exploded above them.

"That was the new TV," Sebastian moaned, eyes drawn back to the internal cameras displaying the ruined family room they had vacated earlier. "It took me three months to convince Uncle Tony to buy that thing; he couldn't understand why I would want to spend $20,000 on it."

"Um, Seb, stop crying over the TV. Our perimeter has been breached and they're flooding into the house."

"Should we release the hair-changing protocol?" Sebastian asked, fingers ready to dance across his keyboard. He frowned as more men flooded in through the indoor pool room.

"No," Blaine responded, also eyeing the group of men in the pool room. "Why don't you use the large scale dryer we installed? I know Aunt Tasha took away the proto-type before we could finalize the outcome, but I think a fire ball would help right about now."

Sebastian cackled gleefully, his fingers dancing across the keyboard, watching as the giant dryer descended from the ceiling and began wrecking havoc. "I'm surprised you're letting me play with this," he commented distractedly to his companion. "You did promise that we would behave while they were gone."

"That was before they broke into the house," Blaine replied darkly, his own eyes tracking over the men spreading out of the ruined living room. "Kid gloves are off." He frowned, watching as they made their way towards the entrance to the lab. "JARVIS, initiate the protocol for biological attack Stephen America," he called hurriedly, watching as the labs were sealed and the men now cautiously coming down the hall way were trapped. The hall filled with gas and Blaine sat back in satisfaction.

"Is that our blue dye mixed with the chemical warfare gun that caused skin boils?" Sebastian asked in awe once the gas dissipated and the men were all passed out on the floor, their skin a lovely shade of dark blue and clearly diseased.

"Yup, with a healthy dose of pass-out gas," Blaine responded proudly before his eyes widened. "Hey Seb," he whispered as a tall man dressed in black with a face mask stepped around the unconscious bodies and headed towards their secret entrance.

"Yeah?" the other boy turned from where he had extinguished the fire he had created in the pool.

"Isn't that Doctor Doom?"

"Oh shit," Sebastian breathed. The Super-villain stopped in front of their hidden door and banged on it.

Turning to the camera, he looked directly into it. "I know you're there, boys, so be nice and let me in."

The boys exchanged panicked looks before Sebastian's fingers danced over his keyboard in hopes of stopping the man from entering. Blaine simply looked on in wide-eyed surprise at the defense protocol Sebastian initiated. Several minutes passed in silence before Blaine found his voice.

"Um, I didn't know we had that protocol, Seb," he offered, watching as Doctor Doom weakly tried to move.

"It's new," Sebastian answered proudly. "I wanted to try it out on Uncle Thor, but I guess this works just as well."

"Do we need to discuss medieval tactics again, Seb?"

"What? I always wanted to tar-and-feather someone," Sebastian defended with a smirk. "So the tar may have been a little too warm..."

Sighing, Blaine responded with a resolute, "Seb."

"Um, boys, what the hell happened?" Tony looked on the carnage that remained in his house. The Avengers had hurried back when they had got word that Doctor Doom was attacking the mansion, worry about the two boys left there evident. "I thought you promised to behave."

"He's been crying like that for the last two hours," Sebastian dismissed in disgust, continuing to tinker with the mask he had removed from the Super-villain. "Some super-villain," he muttered under his breath, his contempt obvious.

Tony turned and studied Doctor Doom with a raised eyebrow. "And why does he look like a chicken?" he asked, taking in the blubbering mess that was the super-villain.

Blaine shrugged, looking up from the gun he had confiscated from one of the attacking men, trying to dissect it. "Seb thought tar-and-feathering someone who attacked the house was appropriate," he offered, shooting his friend a quick grin.

"Your children are a menace to society," Doctor Doom howled at Tony and Bruce as the other Avengers approached.

Sebastian looked up with an affronted glare. "We are not. You trespassed and we took appropriate action."

"And the 'appropriate' action didn't include any of the pranks you two have pulled in the last few years?" Natasha demanded, hands on her hips. She and the other Avengers had done a perimeter sweep, noting most of the 'defenses' used by the boys were their pranks.

"We plead the fifth," Sebastian smirked back. He gazed down at the helmet in his hands. "Can I keep this?" he demanded of Doctor Doom.

"Keep whatever you want, you little devil, " the super-villain cowered back. "Just get me away from these two." Hawk complied, wondering what else the boys had done with the man in their custody for two hours without supervision.

"Alright, Boys, what also happened to force a notorious super-villain to respond to you both in that fashion?"

Blaine looked up with a guilty expression while Sebastian looked proud. "Let's just say, in our defense, he's not the only one who can play at being a super-villain," Sebastian boasted.

"Seb," Blaine groaned, dropping his face into his hands at the astonished looks of the adults.

"I think we need to have another Sensitivity and Responsibility seminar, boys," Natasha stated going over and gripping both boys by the arms before hauling them away from their tinkering.

"But Aunt Tasha – " one of them whined as they were both dragged from the room.

Turning to Bruce, Tony cocked an eyebrow. "You know, I'd hate to see Sebastian left to his own devices," he commented to his fellow Avenger as they gazed at the original hole the boys had created.

"Like Blaine is any better," the other man shot back, crossing his arms defensively.

"Touché, my friend. Touché."

Fin.