This was something I've been working on since August, but I've only just had time to finish x I was reading some stuff and this idea sprung to mind x I hadn't expected to finish this, but today I've had a snow day so I ended up having time xx Please read and review :)

Bruce hissed as the needle pricked his skin, drawing blood. He forced the Other Guy down as he stirred in response to the pain. Bruce already had all of the team's blood; but the main reason for this exercise was to attempt to determine what had gone wrong with his own attempt to recreate the super soldier serum. Well, he knew what had gone wrong (it was big and green), but he wanted to know why.

The lab was clean and sterile and Bruce was being extremely careful - he knew what his blood could do without him even realising it. If any of the team - particularly Tony, who was perhaps the most defenceless and most human of their team and was to one most likely to be poking around in the lab, even more likely to be so than usual should he find out what experiments Bruce was running - were to come into contact with his blood, if anyone came into contact with his blood he'd never forgive himself.

There were many things he couldn't forgive himself for.

Just for curiosity's sake he decided to run a check on the rest of the teams blood to compare them to the super soldiers blood. He started with Thor's - which was fascinating and in complete contradiction of most scientists' concepts of biology. Then he moved onto Clint's and Natasha's and finally Tony's.

At first he thought he'd made a mistake - a contamination. He double checked, using the help of JARVIS who sounded reluctant even if Bruce couldn't figure out why.

It seemed Tony wasn't as human as they'd thought.

He called Tony down into the lab to talk about it. Tony looked at the screen and something dark lurked in his eyes that was quickly and expertly hidden. "I didn't know you were testing blood."

"I was looking at the Captain's."

"Did you find anything?"

"Nothing conclusive at the minute."

Tony peered closer at the screen. "Is this Natasha's? I'm surprised - I'd have though the Soviets would've done something."

"Hmm. Natasha's wasn't what I was surprised with."

Tony tensed, but hid it surprisingly well - Bruce only caught it because he was both looking for it and well versed in reading people.

"Yeah? Something weird with Katniss's?"

Bruce decided to stop dancing around the subject.

"Do you know?"

The room was still. Very still, for just a second.

"Yes."

"What happened?"

"Howard Stark happened."

From what Tony had said - or not said - about his father, it was surprising.

"This stays between us."

Bruce hesitated for a moment before looking, really looking at Tony and finding hints of the vulnerability hiding behind the iron mask. He nodded.

Tony relaxed slightly and turned to strut out of the room.

"Do you want to talk about it?"

His friend froze, halfway out of the door.

"It might help?"

"It might not." Tony didn't sound sure about that.

"You could try."

Silence fell in the lab - it was quiet and still and white. For a moment Bruce thought that Tony would walk straight out.

"Howard wasn't pleased that Mom got pregnant he hadn't wanted kids - not yet anyway. Too busy looking for the Star Spangled Captain. When he was in Ukraine looking he found some notes created by the Soviets. They were experimenting with the concept and Mom was pregnant. It was the perfect opportunity."

"Didn't he test it before hand?" Bruce was horrified.

Tony replied scornfully, "He was Howard Stark. Do you really think he thought he could possibly be wrong?"

Bruce shrugged, not willing to interrupt Tony now that he was talking.

"Everything he did was on purpose. He even made sure that it wouldn't affect my physical appearance."

"When did you find out?"

"I was about two or three. I'd some something - I can't remember what. He'd certainly changed his mind about the experiment. He called me an abnormal freak. When I was five or so he got drunk and told me exactly what that meant. My dad spliced my genes with a cheetah just because he found it mildly interesting. He was never there and when he was he was drunk. And Spangles wonders why I hate him." Tony fuming in anger, stormed out of the room.

Bruce decided not to bring the subject up again - not yet.

Now that he was looking, he could see all of the hints. The way that Tony stilled in conflict and sometimes bared his teeth when he was feeling confrontational. His unnatural speed and grace, that went unnoticed even by Clint and Natasha. His ability to hide in plain sight. The golden gleam in his eyes when they caught the light.
Bruce hadn't discussed it with Tony again but he continued to examine his blood. In fact, he'd actually abandoned his long sought comparisons between his own blood and Steve's - what had gone wrong and isolating the problem would not solve that nor make him feel any better about it. (Actually, finding out where he'd failed might make him feel worse.) Beyond that, Tony's blood was fascinating.

Every look Bruce took reinforced the idea that this was deliberate. Tony wasn't allergic to caffeine and alcohol and chocolate weren't toxic. He could even take most medicine's - the cheetah DNA had been expertly wound into his own genes in a way so that it would minimise the impact on Tony's life.

This was done to show off, to prove that Howard Stark was better than anyone else was.

He couldn't believe that anyone could be so selfish.

And he definitely couldn't believe the admiration the Captain held for him. Tony had very valid reason to loathe his father but Steve wouldn't - couldn't - believe that. Instead he mentioned Howard as a hero, a man to be admired.

Bruce couldn't even bring himself to like the man.

Tony's life had been irrevocably changed on a whim. That had happened to Bruce - and he knew that neither of them had appreciated it.

Loki had escaped his imprisonment in Asgard.

Fury was not at all happy. In fact, he was, well, furious. He was living up to his name in a way that was wholly impressive. When Thor had landed on Earth, using the newly repaired Bifrost, Fury had nearly thrown something at him.

"What shall we do about my brother?" He asked.

Fury almost scowled. "We were hoping you could tell us."

"He will come to Earth to take vengeance for his defeat," Thor said gravely, telling them what they already knew.

"Wonderful. Should we be expecting him any time soon?"

"I do not know when he will arrive. He may be here already."

"I doubt that. It's too quiet. Last time he managed to destroy the SHIELD base, Manhattan and kill a large number of people."

"That really ruined my day. And my suit," Tony snarked.

"It wasn't funny," Steve snapped. Even though the pair of them weren't as bad as they were the first time they'd met on the Helicarrier, perhaps they could even be called friends, they still had bad days. Usually when Tony and Fury stood in the same room for more than ten seconds.

"I never said it was. Maybe you need to check your hearing."

Steve actually snarled, already wound up.

Like before, when the argument escalated, something happened. Maria Hill's voice echoed over the intercom. "Sir!"

Fury immediately stalked out and briskly made for the control room, followed by the Avengers. He arrived to find Agents swarming around like anxious bees. "What's going on?" He snapped.

"We think it's Loki."

Fury gnashed his teeth. "Wonderful," He repeated sarcastically.

Thor was peering concernedly at the computer monitors, looking for his brothers location.

"He's in London at the minute, as far as we can tell."

Tony sighed. "Great. More air travel."

"But you love air travel!"

"Only when it's my suit."

Fury grit his teeth. "Why are you still here?"

The Avengers looked at each other curiously, seemingly wondering the same thing, before all turning on their heels and making for the jet.

"Hill, keep an eye on them," Fury warned, scanning the monitors yet again.

"Yes sir," she saluted before striding on down the monitors.

Fury rolled his eye.

They landed in London relatively quickly, particularly in comparison to other types of aircraft. On one of them, rather than a Stark Special (as they'd been fondly reminded, numerable time on their journey), they'd still be halfway over the Atlantic.

London seemed quiet were they'd landed. There was no one running and screaming, like a bad cliché, and it seemed pretty peaceful.

The thought was jinxed though.

Just as Clint mentioned the calm aloud, of course there was a heart wrenching scream from somewhere nearby and then a hoard of footsteps like a small stampede from the Lion King.

The team prepared themselves for battle.

And stared when a hoard of cats rushed at them from around the corner. Steve looked as though he'd never seen something small and fuzzy before and Bruce, who had already Hulked out, was staring at the purring felines with great puzzlement. He leant forwards experimentally to poke one, before picking it up, surprisingly gently, and stroking it softly.

"Who's idea was this?" Tony asked bewildered.

"Most likely, my brother's," Thor answered promptly.

"You don't really care if we kill him do you?"

Thor glared threateningly at Tony.

He put his arms up defensively. "Okay, okay, okay. No harming Loki. Just the cats."

He looked at them pained. In an odd way they were sort of family, or at least distantly related to him, and he promptly blocked out that thought, realising how weird it sounded. Wwhen had this become his life?

Steve was still looking like someone had killed his dog. He couldn't kill small fluffy house pets!

Tony looked around in confusion. The Hulk was being used as a scratching post for at least twenty of the felines, Steve was slowly bring backed into a wall by advancing cats and even Clint and Natasha were doing their best to minimise damage, if still killing some.

Whose smart idea had this been?

Oh yeah, Loki's.

Tony dismantled the suit slowly, unwilling to fry any of his kin with his repulsors.

"What are you doing?" Clint shouted at him, fending off a ginger tomcat.

Tony didn't answer, instead turning to snarl at the nearest cats, who backed away in fear, recognising a much larger cat. A few of them scampered off down the nearest alleyway, followed by some in the crowd surrounding Steve. They didn't come back.

Slowly, cat by cat, the hoard diminished. Clint, seeing what Tony was doing, tried to hiss at one of the felines but received a claw to the leg for his troubles.

At last, the final cat disappeared off down the alleyway, all except one still being petted by the Hulk. At the Captain's coaxing, the Hulk put the cat down and it scampered off to join its co-conspirators.

The Hulk seemed to pout, before shrinking down the Bruce and passing out on the pavement. Tony reached into his armour to hand him the spare pair of pants he'd carried since the press incident of three months ago.

He then got into his suit, letting it assemble around him, and took off into the sky, knowing that the secret he'd been hiding was about to come out.

Steve looked around confused. Tiny had somehow intimidated a hoard of angry cats that had been trained to attack, Bruce was lying unconscious at his feet and he wasn't entirely sure what to tell Fury. How was he supposed to explain this?

Bruce stirred at his feet, looking dazed. "What happened?"

Clint looked creeped out. "We were attacked. By cats."

"And then Tony drove them off."

Something flashed in Bruce's eyes before he clambered to his feet, looking over them deliberately. "Where isTony?"

Clint shrugged. "Probably gone back to the Tower."

Steve nodded in agreement. "That sounds like a pretty good idea."

Bruce couldn't agree more.

They got back to the Tower quickly, giving a disbelieving Fury at quick explanation and a promise that he could find out more in the mission reports (which only Steve and Natasha ever actually handed in).

Exhausted, they made their way up the elevator, only to find Tony on the sofa whiskey glass well in hand.

"Hey," he acknowledged them softly.

"Hey," Bruce replied soundly oddly sympathetic.

"What was that all about?" Clint asked confused.

"Indeed Man of Stark!" Thor boomed.

Tony shrugged deprecatingly. "Cats have never liked me."

Natasha eyed him curiously. "No. It's something more than that. I've never seen cats act like that around anyone."

"And you would be an expert on cats wouldn't you?" Tony snorted.

Natasha twitched slightly. "It was a mission."

Bruce put a gentle hand on the inventors shoulder. "Maybe it's a good idea to tell them."

Tony threw Bruce a hard look. He backed away with his hands in the air.

"A good idea to tell us what?" Steve repeated sharply.

Tony threw Bruce another look before sighing and leaning back on the sofa.

"That I'm part cat."

There were quite a lot of incredulous questions after that particular revelation. Without answering any of them, Tony rose to his feet and disappeared into his workshop, leaving Bruce behind to explain.

"He's part what?" Steve asked looking lost, as though this is one part of the twenty first century he hasn't encountered yet.

"Cat. He has the genetics from a cat spliced into his DNA."

Steve looks confused. "How did it happen?"

Even Thor looks at him pityingly for that, guessing that however it happened it wasn't accidental. But Steve is too pure for that. He fought in World War Two and he still can't even imagine someone deliberately doing something like this.

"Howard," Bruce said bluntly because he knew this was going to hurt and Tony's hurting as well so he wasn't going to sugar-coat it.

"What happened?" Natasha asked in a tone that was almost sympathetic, because Steve had been rendered mute.

"Tony told me that he was looking for Steve when he came across some notes on transgentics."

Thor very gently interceded, "What is transgentics?"

"It's moving genes from one particular species to another. In this case it's the genes from a cat, specifically a cheetah."

"Why would this happen?" Steve asked horrified.

"I don't know. But it was deliberate. Tony is very sure of that."

Clint asked, "How do you know?"

"It's specifically designed do the genes don't affect his appearance. Things like medicine, alcohol and caffeine aren't toxic. And Tony told me that when he was a child Howard called him an abnormal freak. A few years later he proceeded to tell Tony exactly what he'd done to Tony's body."

Steve looked aghast, clutching hard onto the arm of the sofa. Thor looked distressed, wanting to comfort their 'SHIELD brother'. Bruce knew the feeling.

Natasha and Clint looked an odd cross between sympathetic, understanding and anger. Natasha looked as though she wanted to put a bullet cheerfully into Howard's head and Bruce would've been glad to help her.

None of them knew what to say, so they all just sat there in silence until it became clear that Tony wasn't coming back up.

They don't discuss it again. Not yet.

But now when they look they can't help but notice the golden gleam in his eyes and the predatory gaze when he wants something.

They've all been trained to notice that.

They just don't know how to talk about it.

It's like living on a knife edge, the precarious balance between talking and silence. They haven't decided yet which is better - for Tony, for the Avengers, for them.

But they know that if Tony wants to talk about it, actually wants to discuss it, he'll bring it up with them.

So they stay on the knife edge, watching the cheetah hunt, and none of them say anything.