In Obscuro Speculo

Author's Notes: I don't own the Avengers. Really. Not even stock in Disney/Marvel.

I love AU's that explore what I call "the domino effect": one thing is different, and it changes everything that follows. This is my first attempt at an AU of my own, and was started in response to a challenge at the Beta Branch. As you will see, it's a "what if one rather crucial element of the end of the Avengers movie was different?", and goes from there.

Many thanks to bunch at the Beta Branch, both for the much-needed editing and encouragement. Any mistakes are solely mine.

Chapter 1

He carried his terrible cargo through the glowing portal into stark darkness. Pepper's gleaming image flickered and vanished, Jarvis' voice stuttered and faded, leaving him in the cold blackness with his deadly burden to face the monstrous spaceship alone.

The clamps blew loose, the force pushing the missile forward in its final dash to fate and shoving him back towards the portal.

He watched the missile until it impacted the ship and exploded into blinding light. His eyes slid shut in acceptance as he tumbled slowly through the silent, airless void, the wave of radiation streaking towards him...

XXXXXXXXXXX

Red and gold tumbled in the sky.

XXXXXXXXXXX

Natasha Romanoff saw the gleaming metal form slip though the last tiny bit of the portal before it vanished, and a small smile of relief crossed her face.

A howl of rage from an incoming pair of the aliens on a flier drew her attention down from the sky. Her smile vanished as she dragged Dr. Selvig to cover and returned fire, making them back off. She called into her earpiece as she scanned the area for more Chitauri, "Could use some help here!" She risked a quick look up, expecting repulsor blasts, a metal form blasting rock music coming in for a landing. Her eyes widened in horror as there was only limp tumbling…

XXXXXXXXXXX

Risking a quick glance up after downing another Chitauri, Steve called to his compatriot. "Thor…"

"He's not stopping," Thor said apprehensively. He started to twirl his hammer, only to be tackled to the ground by a determined trio of Chitauri. A wave of their opponents swept over them, and the fight for survival superseded their concern for Stark. A roar echoed over the city, but it wasn't until the green mass clutching battered red and gold armour was halfway down the side of a skyscraper that Steve saw the rescue.

"Over there!" Steve shouted to Thor.

The Asgardian said nothing, but threw his opponents against the nearest wall with grim determination. He swatted the remains of a cab after them to ensure their dispatch before turning to Steve to backhand a determined alien warrior off the soldier. "Let's go find them before this bunch regroups. It looks like they shouldn't be far."

The Hulk was snarling at the small group of Chitauri clinging to the side of a nearby building before he even hit the ground. Steve winced as the green behemoth tossed Stark aside to fall with a clank on the ground. He slid to a stop and crouched beside the red and gold body even as he ordered, "Thor, keep guard with the Hulk."

"Aye," Thor agreed, glaring at the gathering aliens. "None shall get past. Help our comrade." He stood glowering at the Chitauri as Steve hovered over Stark, searching for signs of life while the Hulk looked about, growling ominously.

"I'm not sure what to do," the soldier said uncertainly. "I can't tell anything about him with the suit on."

The Hulk's roar of rage at the sight of a pair of flyers made Steve's heart jump into his throat: not only did it make him in his battle-heightened state physically jump, it also made the metal body in front of him jump as well.

"You're alive!" Steve gasped in relief.

"Yes, and partly deaf now, too," the familiar cocky voice replied. "What's going on?"

"Captain, they're on the move," Thor said softly. "We need your help." Steve looked up: the Chitauri were definitely deliberately moving closer, getting into position.

Steve glanced back quickly when he heard the rasp of metal on concrete. "Stay down, we've got this."

"Obviously, the super soldier formula didn't include the ability to do math," was the weak but determined reply. "There's one hell of a lot more of them than us. You need all the help you can get." There was more of the metal on concrete scraping. "Though if one of you could spare a hand…"

The mass of aliens surged forward even as Steve said, "Not now!" He braced himself behind his shield as Thor started to twirl his hammer and the Hulk roared a challenge. "Let them come to us!" Steve shouted. Protect Stark went unsaid.

The leading Chitauri were in full stride, howling their own challenge, weapons ready… and the leaders suddenly stopped, the following warriors slamming into them, resulting in an unlikely pileup plastered against an invisible wall.

"Od's blood, what's this?" Thor asked, bewildered.

"If they've decided to take up pantomime, ask them to do descending stairs next, I love those," was the suggestion from the ground behind them.

"Sorry we're late, gentlemen." Steve couldn't suppress a shudder of revulsion as he watched a fluid form ooze down the side of a building, clutching a blonde woman in a distorted hand. She had her arms extended towards the four men on the ground, her forehead creased in concentration even as her feet touched the ground. The flowing form gathered at the base of the building and pulled together into the familiar features of Dr. Reed Richards. Overhead, a human-shaped fireball streaked towards the nearest leviathan, while the ground shook under the impact of The Thing's landing in the midst of the wave of aliens. "We had some problems leaving a negatively charged dimension-"

"OK Suzie, I've got these bozos. Drop your shield and let the good guys in on the fun," Ben Grimm rumbled, grabbing an alien by a leg to use it as a club. The Hulk snarled a challenge to the newcomer. Grimm rolled his eyes even as he continued plowing through the mob. "C'mon Jade Jaws, let's see how many more you can smash without smashing me in the process. It's clobbering time!"

XXXXXXXXXXX

The impact against the glass jarred his teeth, but it shattered as he had hoped. He tumbled into the office, narrowly missing desks and chairs to end up on his back, quiver painfully digging into abused muscles.

"You know, I don't think you're supposed do it like that. Landing on your back, especially when you're wearing an arrow holder thingy, is hard on the spine."

Clint Barton turned to glare at the red and blue figure hanging in the window. "No shit." With a wince, he sat up, brushing shards of glass out of his hair. "And it's called a quiver, not an 'arrow holder thingy'. Where the hell have you been?"

"Hey, I had to fight my way here from Queens. Count yourself lucky that I got here in time to see your lame attempt to copy my righteous moves and decided to come over to see if you survived that crappy landing. The swing you did from the rooftop was impressive." The red and blue nuisance prattled on even as he scanned their surroundings for enemies. "For technique, I'd have given it an eight and artistic impression a six or seven, but you lost major points with that landing. The only good thing I can say about it was it was better than the ones done by those three creepy dudes I knocked off the side of the building on my way here."

A Hulk-style roar, followed by a boom, echoed nearby.

"I should get over there," Clint said, climbing slowly to his feet with a grimace. "I may be out of arrows, but I can still shoot a gun."

"Give you a lift?" Spiderman offered. Clint hesitated, wincing at another crash in the distance. "It'll be faster than climbing down twenty flights of stairs." More hesitation. "I'll be extra careful." Clint raised a skeptical eyebrow at him. "Really!"

"I know I'm going to regret this," Clint grumbled as he put his arms around the web-slinger's waist. "Just don't forget about me when you swing over things."

"Trust me!"

XXXXXXXXXXX

The flyers were still soaring around the rooftops. Natasha ducked for cover behind the generator, pulling Dr. Selvig with her. She turned to him, shaking his arm to draw his attention back to her from the aliens.

"Doctor," she said urgently, "how do we disable the machine? If we don't, they might figure out how to restart it and we will have to do this all over again."

He visibly pulled himself together, focusing past his mental confusion to the necessity of now. "We - we need to pull the tesseract out. Without it as a power source, the machinery is useless. The case for it-" he looked around wildly, panic starting to surge until she laid a soothing hand on his arm, "- it was beside the monitor."

"There it is," she said spotting it behind some debris. She calmly retrieved it and looked at him expectantly.

"We need to pull out the cube and put it into the case," he said. He turned to the portal generator and hesitated.

Natasha stepped forward. "If you tell me what to do, I'll help you," she offered, one eye to the sky. "We need to do this quickly, before they realize how defenceless we are up here."

He nodded, face twisted with conflicted emotions. "You're right. I - I've lost the tongs for handling the tesseract." Shame crossed his face as he picked up the keyboard.

She looked into his face. "And you don't want to risk touching it." She simply stated the fact, no censure in her voice. She squared her shoulders, staring into his eyes. "Can I handle it without the tongs?"

"It should be safe," he said, "the portal isn't functioning, so power levels are low." He carefully tapped the controls, and the brackets holding it in place loosened.

"You should be able to reach in and take it out now," he said, opening the case. "You'll need to take the sensor wire off the side, and try not to touch the base of chamber."

She reached in gingerly, first carefully pulling off the sensor wire, then gently grasped the glowing cube with a gloved hand. Quickly, she pulled it out of the machinery and set it into the case Selvig held. He slammed it shut with a shudder, sweat mingling with the blood from his head wound to trickle down his forehead.

"Thank god," he gasped, shaking.

"Are you all right, doctor?" she asked, worried.

"I'll be fine," he gasped. "It's just - seeing it makes me remember things she showed me. I - I need to forget…"

"You'll be fine," she said reassuringly. "We'll get you help." She looked over his shoulder, frowning, at the penthouse. "I do need your help with something first."

XXXXXXXXXXX

Frank Castle bared his teeth defiantly as he watched the massive leviathan soar to the northwest of the city. He fired a rocket at it in the vain hope of causing it damage before turning back to mow down the last of the alien scum behind him. When he was able to look back up, the giant beast was already a small shape in the distance.

"Someone else is going to have to deal with that mess," he growled. "Lucky break for those alien bastards." He rolled his shoulders and checked his ammo as he jogged towards the sound of more alien shrieks. Time go hunting.

He smiled.

XXXXXXXXXXX

"Sue, please put your shield back up around us," Reed Richards ordered as he knelt next to Tony. "Mr. Stark, how can I help you?"

"I can figure this out-" Tony started.

Richards interrupted him briskly with an impatient wave of his hand. "I'm sure you could do it yourself, but time is of the essence. Stuff your ego and let me help."

Stark's mouth snapped shut and he glared at Richards. The scientist glared back. The engineer finally relented with a sigh. "Fine. There's a panel on my left hip…"

After twenty minutes of intense arguing, Iron Man was back on his feet, with Jarvis fully functional. "There's no way to get you enough power for flight," Richards said as he admiringly examined the circuitry connecting the arc reactor to the repulsors, "but you should have enough power to put up a fight and keep Jarvis functional."

A blazing form swooped up to hover overhead. "The National Guard is here and working with the NYPD on 39th to go building to building," the Human Torch said. "I'm going to help them."

Richards turned to Rogers. "You have things well in hand here," he said, watching Thor slam a Chitauri into a wall while the Hulk snarled at a lonely incoming flyer. "It's our turn - we'll go help them. Stay here and wait for anything we flush out down here."

Rogers looked around him at his companions: Thor was definitely moving more deliberately, favouring his left side, Stark was carefully expressionless as he checked his gauntlet repulsors, and the Hulk… The Hulk would definitely need to calm down if there weren't any more Chitauri on hand, lest his rage overflow into general destruction.

He nodded tersely. "Go. We've got this."

XXXXXXXXXXX

In Hell's Kitchen, Daredevil tossed a pair of Chitauri from their flier. On the ground below, as Iron Fist punched one of them from mid-air to land in a steadily-growing pile of alien bodies, Luke Cage grabbed the other by a leg, while the man without fear leaped off the flier to let it crash into the Hudson.

"Where the hell did these bozos come from?" Luke Cage growled as he used the alien as a club on three more of the alien ground troops. "I was all set to go home for a beer and watch the game."

"Wherever they come from, they don't come in peace," Iron Fist replied, tossing a weapon onto another pile. "I think the game probably got cancelled."

Daredevil cocked his head as he stood on a nearby fire escape, listening intently. "The worst is over by Stark Tower: the portal these things were coming out of was directly over top - " he stopped with a wince and gasp as a roar echoed through the streets, followed by an explosion in the opposite direction, from Harlem. "Between the Hulk's roaring and Castle's explosions, I'm going to end up deaf."

"Look!" Luke pointed.

"Not happening until my ears stop ringing," Daredevil complained.

"Two of those giant flying things," Luke explained. "One's flying southeast out over the ocean, way faster than before. The other one… is going southwest." Dread washed over the three heroes.

"They plan to do this across the world," Iron Fist said grimly.

XXXXXXXXXXX

Zip

"Are you sure that'll work?"

Zip

"Those don't look very thick."

Natasha gave Selvig a look of the sort that in the past had made Fury himself pause. "They are much stronger than they look," she said mildly.

"It's just, well," Eric Selvig fidgeted, knowing he was pushing matters, but his understandable anxiety forced him to continue. "Asgardians are much stronger than humans. Do you really think those will be strong enough?"

She gave the zip tie securing Loki's wrists an extra tug. "Can you grab that chair over by the bar for me? Oh, and one of the bar towels." The nervous physicist scurried over to the bar and, after retrieving a towel, dragged the indicated chair over to her.

"Now what?"

"Sit down on the chair and give me your socks."

"My…" He swallowed the question as she glared and did as she asked. "Um…Do you need my shoes?"

"Nope. Just the socks. Better put the shoes back on." She gingerly picked up the socks, keeping them at arm's length. Chagrined, Eric suddenly realized that he was still wearing the same clothes he had on when Loki had arrived two weeks earlier.

"Now what?"

She made sure she was leaning over Loki's ear as she said, "Hold the chair over your head."

Nervously, he did as he was told. "Um, do you mind if I ask why?"

She leaned closer to Loki's head as she wedged his jaw open. "Because if you hear so much as a whisper, see him do the tiniest twitch, I want you to hit him with the chair."

"I don't need to hold it over my head to do that."

"If he tries to incapacitate you, the chair will fall and still hit him."

"Right." Smirking, he carefully aligned the chair for optimal angle. He watched as she stuffed the socks into Loki's mouth and used the towel to secure them in place. Puzzled, he asked, "Wouldn't the towel alone have been enough to gag him?"

She raised an eyebrow at him. "Probably. But not nearly as nasty as he deserves." She added another zip tie, this time to immobilize the Asgardian's fingers. "You can put the chair down."

"You're sure?"

"Yes, I'm sure. It's not good policy to hit people on the head if they're defenceless: review committees take a dim view of that," she said with a shrug. "Besides, I want you to help me drag him out onto the roof. That should also be very uncomfortable and embarrassing for him, but it's necessary and we can't pick him up easily, so anyone doing a review of this later can't complain."

For the first time in weeks, Eric Selvig smiled.

XXXXXXXXXXX

"There they are - whoa!" Only extraordinary reflexes aided by his spidersense saved Spiderman and his passenger from being smeared into the side of a building by a flying slab of concrete. "Take it easy! We're the good guys!"

"Stand down, Hulk," Captain America ordered. "Who are you?"

"Just your friendly neighbourhood Spiderman." The red and blue form flipped off a jaunty salute as he cautiously slid down a web line. "I'm here to return one of your lost lambs."

The hero looked more closely at the dangling forms. "Agent Barton. Good to see you are all right." Cap nodded in acknowledgement. "Many thanks."

"Thanks for the lift," Barton mumbled, jumping free. The SHIELD agent looked like he was seriously considering kissing the pavement.

"Any time," Spiderman said, clinging to the side of a building. "I generally specialize in damsels in distress, but when alien invasions happen I'll make an exception." He glanced around. "You seem to have thinned them out in this area: I think I'll join the Fantastic Four uptown to party with the National Guard and NYPD." He jumped off the side of the building, shooting webbing at another one to swing away in his usual style. "Later!"

"Strange way of getting around, but he really makes good time swinging around like that," Cap mused.

"Trust me Cap," Barton said, pulling out his pistol to shoot a Chitauri charging up behind Thor, "you never want to travel like that. Ever."

XXXXXXXXXXX

In Greenwich Village, a brownstone sat serenely undisturbed amidst the chaos. Humans unconsciously avoided it, running around it to other buildings, not even noticing the dim light in its windows. A dog, whimpering in fear, started to run for the calm of its steps, only to stop, back away a few steps, and then bolted for the end of the block yelping.

A squad of Chitauri paused in their pursuit of some humans to stare at the innocuous building. The leader sniffed the air, curious - there was a strange scent of power, irresistible to his kind. He signalled the rest to follow and charged forward…to suddenly vanish in a flash of light. The rest skidded to a halt before impacting the invisible barrier as light swirled to form letters in Chitauri dialect: I am not home. Do not trespass.

XXXXXXXXXXX

Natasha huffed in exasperation. "There's too many of them." She threw a quick apologetic glance over her shoulder at Selvig. "I'm sorry, Doctor. This is likely not going to end well."

The doctor nodded in understanding and gripped the case containing the tesseract tighter as he kicked the sceptre and Loki further behind him, tighter to the building's ventilation system. "Give me a gun," he suggested. "I don't have a very good aim, but if they get close enough it won't matter."

Wordlessly, she studied him intently for one brief second. With a brief nod, she pulled out her small backup piece and handed it to him. "Don't shoot unless you absolutely have to," she instructed.

"No problem," he agreed, nervously pointing it away towards the ground. He shrank back behind her as she turned to face an incoming flyer. "I think-"

A bang behind her made her jump. She spun, gun ready, only to find a swirling black cloud where he had stood: she charged through it, coughing from the sudden stench of sulfur as she frantically scanned the rooftop in vain for the physicist.

She turned back to face her captive, eyes narrowed. Loki's eyes widened as she took precise aim between his eyes. "I don't know how you did that, but you have precisely five seconds- " the assassin growled.

The banging sound interrupted her and she swiftly pivoted to see a blue tailed form reaching for her. Yellow eyes widened and the form vanished into a black swirl as she fired.

She took aim again at Loki. "Is this another one of your allies, Loki? Or another one of your tricks?"

"Actually, Agent Romanoff, Mr. Wagner is neither, and I would very much appreciate it if you didn't shoot him." The voice was eerily quiet. Too quiet: her skin crawled as she suddenly realized that she wasn't hearing with her ears. "We will move our plane closer so you can board. Please do not shoot us."

Her gun didn't waver from its aim at Loki's head as a plane silently rose into sight beside the rooftop. It hovered quietly, gracefully pivoting to lower a rear ramp to the roof. She blinked but didn't move when a man made of steel jumped out, followed by a white haired black woman and three men in leather outfits.

"Colossus, get the Asgardian and the equipment aboard," one of the men ordered. He scanned the sky, one hand at the strange visor covering his eyes. "Storm, you and I are going to pick off any fliers that get close. Iceman, some cover for Agent Romanoff and the Blackbird." He turned to the third man. "Wolverine-"

"I'm going hunting," the third man announced. Metal claws popped out of the back of his hands as he eyed one of the fliers drawing close with a feral grin. "I'll deal with this one." He rolled his shoulders, cracked his neck. "Don't wait up." He took a flying leap off the roof to land on the flyer, and rapidly spiralled out of sight.

The leader sighed even as he turned to face the incoming aliens. "Bobby, look after things here. Storm, let's kick some ass." He turned away to suddenly have a stream of violent red light stream from his visor, as the woman's eyes turned white in the sudden lash of wind. Stormclouds suddenly gathered around the tower, and Nat saw lightning lash at multiple fliers before a wall of ice blocked her view.

The young man called Bobby turned to her, and courteously gestured to her to board the plane before he did. "Agent Romanoff, please don't worry. We'll get you to safety."

She eyed him darkly, but said nothing as she warily stepped around the steel man to board the plane. "Make sure Loki's gag stays in place," she ordered as she watched him carry the Asgardian. "And be careful with the apparatus. I'm sure that there a lot of people who will want to take that thing apart very carefully to figure it out."

She turned to the bald man in the wheelchair. "I need you to take me to the SHIELD helicarrier. Now."

XXXXXXXXXXX

"That's the last of them," Barton announced, watching the last flyer crash into the street.

"For now," Stark said, scanning the sky. He flipped up his face mask, letting them see him frown. "There's a small black cloud over by my tower. And…I just saw lightning. Point Break, you have anything to do with that?"

"No," Thor said, frowning as he followed Stark's line of sight. He started to twirl his hammer. "I should go investigate."

"Never mind," the billionaire said. "It just vanished." He sighed. "Just what we need today: funky weather to go with an alien invasion."

The Hulk looked up, snarling, flexing his massive hands as he searched for more foes.

Rogers stepped in front of him. "Hulk, stand down." He didn't flinch at the answering snarl. "Stand down. The enemy is not here anymore. Dr. Banner, we need you to calm down."

Emerald eyes glared at him, and for a minute Rogers thought the monster had won. Then, the green rage faded to exhausted brown eyes and Bruce Banner was with them once again, clutching the tattered remains of his pants.

"Welcome back, Dr. Banner," Rogers said.

"Thank-you," Banner said, moving slowly to sit on the hood of a cab. He looked around at the general destruction with a sigh of resignation. "I imagine the Other Guy caused a bunch of this."

"Don't worry," Stark replied. "We'll send a bill to the Chitauri for the stuff not covered by insurance. With interest." He eyed Banner with a snort. "Rather than dazzle us with your manly not-green chest, why don't you go rummage up some clothes?"

"I'm not a looter," Banner retorted, with a stubborn set to his jaw.

"Just go get a shirt and a fresh set of pants," Tony retorted. "There are advantages to knowing a rich philanthropist: if insurance won't pay for it, I will, or I might even buy the shop if they're really huffy about it." He made a shooing motion. "Go. We don't need you to distract the ladies of the fire and ambulance departments."

XXXXXXXXXXX

"Is that it?" the Human Torch asked as The Thing tossed a final Chitauri into the growing pile. He landed next to his brother-in-law to watch him disassembling one of the aliens weapons. "I don't see any more, and the army guys and cops haven't called us for a while."

"Looks like it," Spiderman replied as he checked the pair he had webbed to the side of a building. "Hope so. There's way too many of these guys to make them all sit in a corner for a time-out already."

"There's four more!" Sue Storm pointed at four small flying forms retreating south.

"Want me to go after them?" the Torch asked, flames starting to gather around him.

Reed Richards looked up from the weapon. "No need." He smiled grimly. "That area's well taken care of already."

XXXXXXXXXXX

"Get ready people," Steve announced, "we've got incoming." He pointed out four flyers coming towards them.

Banner jogged back from his reluctant scavenging, new shirt hanging unbuttoned, shoes and water in hand.

While he was sure the Asgardian would never admit fatigue, Steve noticed Thor's motions were more deliberate than they were earlier. He knew his own reactions were growing slower, and his abdomen still throbbed from the shot he had taken earlier. Tony had no qualms about letting his exhaustion show - he stayed seated on a car hood as he accepted a water bottle from Banner, sipping as he watched the flyers, while Banner merely eyed the incoming aliens with a shrug as he offered water bottles all round.

As the flyers drew closer, they could hear the challenging howls of the Chitauri. Tony flipped down his faceplate and wearily climbed to his feet as Thor started to twirl his hammer…

Four missiles streaked through the air, turning the flyers into fireballs. Thor turned and saluted the quinjet wearily with his hammer, exclaiming, "Well met!" Steve sighed in relief, lowering his shield, Bruce slumped against the remains of a cab as the tension left his body, while Tony calmly flipped his faceplate back up to take another swig from the water bottle in his hand, only a tremor in his hand betraying his relief.

The quinjet delicately settled down in a relatively clear space. Its boarding ramp lowered and Romanoff casually sauntered out. "Hi guys. Need a lift?" Despite the grime and blood, she looked like she had been out for a Sunday drive.

"We should stand by in case there are more-" Steve started.

"The National Guard, NYPD and other super-powered individuals have things well in hand. Loki is locked down in a cell on the helicarrier. Scanners on the helicarrier detect no more alien forces in this area, and Director Fury needs to debrief you," she interrupted.

"We should check in with them before leaving the scene-" Steve persisted.

"Before we go anywhere, we need to eat," Tony declared. "I don't know about the rest of you, but I'm starving. Fury can wait a bit longer."

They all looked around at each other. Bruce shrugged, "I admit, I could use a bite."

"Agreed," Thor boomed enthusiastically, clapping the scientist on the shoulder.

Rogers was visibly conflicted. "We really should report in," he said, but lacked his usual conviction.

"Cap, you need to refuel before you do a face plant. There's a non-destroyed shawarma place two blocks over," Tony suggested. "I've never had it before and have no idea what it is. Let's get some."

"Why not?" Barton shrugged with a wry expression. "I'm sure there's a lot of other things Fury can deal with before us." He turned to Romanoff, his eyes inscrutable. "Coming?"

She hesitated, eyeing them intently. Stark was carefully neutral, Banner was apologetic, Rogers was hopeful, Thor beamed enthusiastically, and Barton…

She smiled, a small, genuine smile. "Of course. But only if Stark's paying."