Disclaimer: I do not own the Avengers or the Dark Knight characters. Hope you enjoy, don't be afraid of the review button! I really have no idea where S.H.I.E.L.D's base is, but it can move (right?) so I'm gonna say that they parked it near Stark Towers.

Prologue:

The first time that Natasha Romanov saw Catwoman was at a demonstration in Gotham City. S.H.I.E.L.D had been hired to help with security, and she was about the best security you could get. It helped that the young assassin could blend in much better than a police force, but she was twice as deadly.

Natasha was dressed in her civilian clothing- stretchy skinny jeans, a simple black t-shirt, and combat boots. She had two hand-guns underneath her brown leather jacket, and a knife within the sole right boot. She watched as Commissioner Gordon delivered a speech about rebuilding Gotham at the podium in front of City Hall. She respected his vision for the future, and how he never seemed to give up hope, even after all that happened involving Bane.

Natasha was sorry that the man would soon retire, because he was one of the good ones. That was why she hadn't turned down such an easy job. It was a cut-and-dry public service assignment, keeping the piece during Gordon's address. There had been much unrest in Gotham, even after Batman had killed the Bane's reign. Personally, Natasha had doubts that the city would ever be the same, even if a new hero was rising from its ashes.

"There will always be someone who can carry this city, someone with hope and conviction. I will never give up on Gotham, and I only ask that the people do not, either." Gordon was saying.

Someone in the crowd caught Natasha's attention. It was the spy part of her, the attentive part of her brain that would instinctually react to things out of the ordinary. And though the woman across the courtyard looked perfectly normal, to Natasha's trained eye, she knew that she was too lithe, and her movements were too calculated.

The other woman was tall, with long legs covered by nylon tights, and she was wearing unassuming dark dress. Natasha could only see the woman's profile, but from what she could see, she had arched eyebrows and pouty red lips. Her dark hair obscured the rest of her face.

Suddenly, the courtyard was filled with the sounds of gunshots. Of course, people panicked, as was expected. But Natasha identified the people holding the guns instantly. There were only five of them, all stupidly gathered closely together.

Natasha watched the slender woman from the corner of her eye. She started to go to incapacitate her as well, but realized that the woman didn't seem to be with the thugs. She was just riding out the chaos and stealing a couple of wallet along the way.

One of the gunmen still waved his gun around, like he was expecting Gordon to cave just because of that. Natasha took this as her signal and started to wade through the crowds. Enough people were running around to cover her advancement towards the men.

She passed by the woman, who had at some point slipped a mask on over her face. Within seconds, Natasha had paralyzed the first gunman's arm and was shooting his accomplices with his weapon. She was careful to aim for the legs, because Gordon had explicitly requested that she not kill anyone.

She ran to each of the men whom she'd shot, plucking their weapons from their grasp. She wasn't quick enough to get to just one man, who aimed shakily at a little boy who was watching the scene with horror.

Natasha's eyes narrowed. She would have to kill this man. She was probably fast enough, but if not... casualties were often inevitable.

She rushed to stop the masked man's finger from pulling the trigger, but his hand was broken before he had the chance. The woman in the black mask had the man's wrist pinned with one high-heeled boot, while the other one was crushing the hand holding the gun.

"You'd better let go before you hurt yourself, hun." She grabbed the gun as he screamed and tossed it to Natasha, who was trying to hide her surprise. Black Widow was never surprised, or so she liked to tell herself.

"Don't mind me... I was just leaving." The masked woman purred, bolting before Natasha had a chance to speak. She hopped over a wall, and the last things Natasha heard was the whirring of machinery... maybe wheels?

Curiosity peaked, she called Fury and issued the all-clear as members of SHIELD and Gordon's team lead away the assailants.

Mission accomplished. But she'd found a little mystery in the process.

Facial recognition had come up with a blank from Natasha's footage. That was strange enough, given SHIELD's advanced technology. Only people who had something to hide would be absent from the database. Natasha then thought that the woman must be a criminal of some kind.

Tony had come entered his lab to find Natasha pouring over the computer.

"Anything that I can help you with, Dollface?"

He'd shut his mouth at the cocking of her gun, pointed at his head. "Don't ever call me that again. And I'm trying to find someone."

After regaining his power of speech, Tony grinned, "I hear that E-Harmony is good for that kind of thing. But we're definitely going to have to work on your profile, because the occupation of "assassin" isn't exactly a deal breaker."

"Shut up, Tony, before I really do blow your head off. And get out if you're not going to help."

Tony ignored her, instead examining the footage of the rally in Gotham that was replaying on the screen. Everything was from Natasha's point of view. He saw her beating men to the ground (nothing new there), but then the view focused on a woman... in a cat mask.

"Hey, I recognize that mask! It belongs to Catwoman."

"Catwoman?" She said, irked that Tony Stark knew something that she didn't.

"Yeah. I mean, she's a sexy villain in a tight-fitting outfit that shows off curves in all the right places, and who dresses up in a cat costume for a living. Of course I know about her. Although officially, she and her true identity don't exist anymore."

Natasha snorted. "And unofficially?"

"She may or may not be Selina Kyle, the main squeeze of the late Batman."

Present Day:

That was over a year ago. Natasha had never stopped keeping tabs on the young cat-burglar. Something about Selina Kyle was just too good to ignore. She never did anything sinister enough to warrant SHIELD stepping in, so they let the Catwoman continue doing what she did best- stealing from the rich. She was no Robin Hood, though; she took what she got and kept it. But she was careful to never leave a trace... but SHIELD knew that when something disappeared, Catwoman had probably been there.

"Natasha here has got a little girl-crush," Tony teased her one night, "On Catwoman. Maybe she's just jealous because you both look so damn good in leather."

Natasha had promptly kicked Tony so that he landed square on his butt.

"What? It's like every guy's biggest fantasy: Two hot chicks in spy costumes duking it out. May be add in a little jello or whipped cream..." Tony complained from the floor. Natasha looked around the den at the other Avengers, none of whom were denying it. Except maybe Bruce, who was reading a scholarly journal and probably wasn't even paying attention.

"You're impossible." Natasha told him. She decided that it was time to go to bed and get some beauty rest. Her face was half of her job, after all.

"You know, you could always just leave some cat-nip outside your door or something. Maybe you'll lure your lady-crush here!" Tony yelled after her. She resisted the urge to turn back around and strangle Tony with Pepper's hair tie.

It was ironic how true Tony's words really were, because just two days later, they were awoken by Jarvis sounding an alarm—meaning that Fury really wanted to talk to them.

"We've got company here on base. Someone let a stray in." Fury appeared as a hologram once they were all together in the den. He was practically sneering as he said,

"Catwoman's showed up."

Tony elbowed Natasha, and she glared back.

"Black Widow, Barton, you take care of it. I don't want to get my other men involved unless they have to."

"You're sure we can't join in, Sir?" Tony asked, uncharacteristically respectful to Fury.

"I think we can handle a stray cat." Clint bristled.

"You don't understand, Buddy. I just don't want to miss the girl-on-girl action! It's gonna be quite the show!"

Natasha didn't grace this with a response, and instead swept out of the room. Clint followed close behind.

"And Natasha," Fury called out after her, "Try to capture her alive!"

"Understood, Sir." She said quietly to herself, secretly thankful that she wouldn't have to extinguish such a promising life.

Clint picked up his bow and arrows along the way as they headed to where the video had been cut off on the base. It was just on loop, and they both wondered who was brilliant enough to tamper with S.H.I.E.L.D technology.

Catwoman had already been inside for at least thirty minutes, and that was plenty of time to steal if you were good enough to bypass the security.

"There!" Natasha said, running after a shadow that she saw going into the boiler rooms. Clint ran after her, and they stepped lightly within the gloom. Someone, probably Catwoman, had cut the lights.

"Here, kitty kitty kitty!" Clint sang to himself, listening for any sounds in the base. Selina, who was hiding behind a large pipe, held her breath as he passed. A drop of sweat fell down her temple. She started to slink out but was blocked by Black Widow, who grabbed her shoulder.

She spun out of the red-head's grip and aimed a kick at her head with the momentum, which Natasha blocked easily. Natasha tried to get Catwoman off balance by jabbing her from both sides, but Catwoman held her ground, even landing a couple of hits herself. When Natasha missed a kick, Selina grabbed the other woman's leg and tried to throw her. Natasha just continued with the momentum and back flipped away.

Clint, who had been waiting to get a clean shot, stared after the woman in amazement. "Jesus, she's fast!"

Maybe even faster than me. Black Widow thought, but barked, "Don't just gawk at her! Move!"

Selina wasted no time getting out of the boiler room, booking it until she got back to a room with access to the venting system. She punched a button which did exactly what she'd hoped, shutting a metal door behind her. She slid on the floor underneath it as it closed.

Her heart was slamming in her chest as she reached the grate. She snorted. For as advanced as S.H.I.E.L.D defenses were, she couldn't believe how easy it was to get around once you were in.

She took out a pen-like item that shot out a red energy beam, strong enough to cut through small amounts of metal. It did the trick on the grate, and soon she was sliding in. Just moments later, she heard the door behind her explode into pieces, and the Avenger's voices.

As she climbed through the vent system, she thought only of getting out of the ship. She'd parked the Bat-cycle (as she called it) on the ground, and she didn't think that the SHIELD base had moved. She just needed to get out onto the top floor, where she could propel herself down.

Meanwhile, Natasha and Clint realized what she had done.

"All of the vents lead to the top of the base." Natasha said. "We just need to get below her... and then force her out."

"Alright." Hawkeye agreed. They went up a floor and Natasha pointed at the ceiling. She could barely make out a squeaking sound of movement from above them.

She nodded, and Clint loaded up and arrow. When she mouthed "now", Clint let his arrow fly. There was a small boom, and a portion of the ceiling fell, leaving Catwoman clinging from the edge of the metal tube that she'd been crawling in.

Natasha shot a bullet at her at a wicked speed, but missed as Selina dropped to the ground in a graceful roll. She came to a standing position and eyed the SHIELD assassins.

"I didn't think they'd send the big dogs after me... I'm flattered." She said, trying to distract them. It was obvious that Natasha was having none of it. She kept the gun trained at the woman.

"Come on, why don't you loosen up a bit, Widow? You've already got me cornered." She said.

"Animals that are cornered have the sharpest claws." Natasha threw back.

"Well... you got me there." Selina smirked, and whipped a few spherical things out of her belt, throwing them at the agents with lightning speed. She'd "borrowed" the ball-things from Bruce Wayne before she'd left, and she'd had no idea what they did... but apparently they provided a smoke cover. Natasha pulled the trigger instinctively, and Clint sent out an arrow aimed at Catwoman. Seeing both coming, she had time to dodge the bullet as she did a back flip away from them, the arrow only grazing her shoulder. She hissed as another arrow bit deeper into her side. Hawkeye was a better marksman than she'd thought, able to shoot using senses other than his sight.

"Courtesy of Bruce Wayne." She smirked, kissing the spare bomb in her hand reverently and tucking it back under her belt. Sometimes it rocked to be in a relationship with a super-genius who had enough money to make great tools.

Ignoring her pain, she ran at the wall furthest away from Natasha and Clint, using it to give her height as she pushed off it with her foot. She turned mid-air, wincing as her wound flared at the movement, and threw her hands out to catch the ledge that she'd fallen from. She grasped it and started to pull herself up.

Natasha coughed and blinked as tears streamed from her eyes. The entire room was full of black smoke. She blinked enough of the stinging away and saw Catwoman scrambling up onto the next floor.

No! She thought, but was mildly impressed at the woman's ingenuity. She touched Clint's shoulder to let him know that she was there, and then said, "I need a boost."

They'd been in enough battles together for him to know what she wanted with very few words. He kneeled down and braced his hands so that she was able to fit her foot onto it. With a surge of strength, Natasha launched herself from Clint's grasp. She leapt higher, higher into the air, and reached for Catwoman's still dangling foot. The two fell in a tangle of struggling limbs with a resounding thud. Both women were on their feet almost instantly, though Selina was feeling the brunt of the fall. She let out labored breaths through her bruised ribs.

The smoke was just thin enough for Clint to see the end of the brawl unfold. Catwoman was avoiding Natasha's strikes, but it was obvious that her pain was slowing her down. Natasha took out her gun, which to Clint's astonishment, Catwoman pushed away with one hand, and her other fist collided hard with Natasha's jaw. This sent Natasha sprawling, while Clint couldn't suppress a laugh. No one ever punched the Black Widow!

Natasha threw herself at the Catwoman with a seemingly renewed vigor, quickly subduing her opponent. A few punishing kicks and jabs later, Natasha was poised above Catwoman with her boot crushing the cat-buglar's windpipe and her gun trained at the woman's head. Both were panting heavily, and Clint had to admit that it was one of the most erotic things that he'd ever seen.

I guess Tony was right.

About twenty minutes later, Selina woke up in a cell combined with an interrogation room. They'd knocked her out after the fight.

Wonderful. she thought. I guess I should be getting used to this, though.

And she realized that she was lucky to be alive. Seeing the barrel of a gun so perilously close to her head still sent chills through her. She may have been a thrill seeker, but she wasn't seeking death. She was a thief first and foremost out of necessity. Her joyride through S.H.I.E.L.D had been an exception... a misguided exception.

She found herself staring into the eyes of her almost-killer, and her sidekick.

"Just relax, try to make yourself comfortable." Clint said from where he was seated backwards in his chair. "I hope you enjoy your stay at Chez S.H.I.E.L.D."

"Well, this wasn't exactly how I planned on spending my Saturday night." She gave Clint a forced smile. She wriggled her hands, which were bound by metal cuffs to the chair. Her side hurt much less than before, and she wondered if they had something to do with that.

"That was certainly an impressive demonstration... Miss Selina Kyle." Natasha said thoughtfully. She was seated on the table. Her nose was swelling slightly, to Selina's satisfaction.

"You know who I am, then." Selina's eyes narrowed, and she shook her head. "And you probably knew I was coming from the beginning. Bruce warned me about you guys... you really are in a league all your own."

"Yet you still though it was a good idea to try and steal from us?" Clint said with amusement.

She shrugged. "I wanted to see if the rumors were true."

"And do we live up to your expectations?" Natasha asked a little cruelly. She began cleaning her gun with a cloth, hoping to make the buglar squirm.

"Unfortunately, yes. Still trying to decide if getting my ass kicked was worth it." Selina grumbled. Natasha could see that the brunette was scanning around her for a way out.

Good, the spy thought, She hasn't given up yet. She's vigilant... also good.

"So you weren't here to steal something in particular?"

"Ah, so it's interrogation time." Clint told her. "You'd better just fess up. Tasha is no fun when she's mad."

"Let's don't, and say we did?" Selina suggested, winking at the archer. "Unless you want to bring out the whips and chains. In that case, be my guest."

"Sorry, that's a no go. Whatever Tasha's got planned is probably ten times worse. If it were me, I'd just try to make this as painless as possible."

Selina seemed to ponder her words for a moment. "I was curious, more than anything... but I have heard whispers. There's talk of an enormously powerful item that you people now have in your possession. It's said to contain enough energy to destroy the world... if it fell into the wrong hands. Just think of the possibilities, huh?"

Natasha felt a cold shock go through her. The woman was talking about the tesseract.

"And how is it that you found out about this story?" She said stiffly. Outwardly, she looked completely unfased though. Keeping her emotions in check was one of her many talents.

"A little bird told me. And before you ask, I couldn't tell you where she is right now. Last I heard from her, she was in Cabo... but I can guarantee that she won't be there when you look."

"You won't give up the identity of this "little bird?"" Natasha guessed.

"I'm sure you'll hear about her soon enough, so no harm in a little gossip between us women. She's known as the Red Fox in the underworld," Selina said, "You should all consider yourself lucky that she isn't swayed by physical things. Not even S.H.I.E.L.D would stand a chance if she wanted something from you. She's the queen of secrets... and something tells me that S.H.I.E.L.D has a lot that they're trying to hide."

Natasha's brain was going a mile a minute. This Red Fox person sounded like she was a possible threat... but she'd never even heard of her.

"So... what are you people going to do to me, anyway? Because I think I'd like to request a phone-call."

"We're one step ahead of you, Miss Kyle," Clint grinned, "Luckily, you had your kitty-tags on. We'll get you home safely, don't worry."

.

Bruce Wayne received a phone call from Phillip Coulson that night.

"I don't suppose that you're missing a few important things, are you, Wayne?"

"Not that I know of... why?" He asked, puzzled.

"It looks like some smoke bombs have walked out of your hands."

He groaned. "You must have found my lost cat. My things have a habit of disappearing when she's around."

"I expect you want her back, then?" Coulson fought hard to keep his voice professional, because he could imagine Bruce Wayne's frustration on the other end.

"Sometimes, I wonder. She's really nothing but bad luck."

There you have it... a sexy Selina Kyle mixed with the deadly Black Widow. I hope that I did okay with the fight scenes, because it's hard to translate them from my head into words! Review, pretty please, I love my readers even more when they do.