Technically, this is set after 'Casey Jones vs The Underworld, in that it accounts for everything that happened prior and not anything after, since nothing else has aired yet. But since a new episode's meant to air in, like, five days, my canon could be jossed pretty quickly, which is why I posted it now instead of waiting 'til I'd finished the whole story as I planned.

Also, first TMNT multi-chapter fic. So, yeah, that's a thing :)

Disclaimer: I don't own any version/incarnation of TMNT, otherwise I wouldn't be writing fanfiction. I would, you know, be making the rest of Season 3. OMG WAITING IS KILLING ME.

She was everywhere. No matter which way he turned, which way he swung, the clash of metal on metal told him she was present. It was a type of fighting he recognised from Raphael: inescapable.

Only, this was still very different to Raphael's style. She wasn't just in front of him, she was in front of him, a few inches closer than she needed to be. She didn't just stand behind him, she stood behind him, breathing down his neck and leaning into his shell. Her body curving over his back was all he could think of, even as she pressed her sword to his throat from behind. The intoxicating scent of her that lingered after her departure and the memory of her velvety voice stood out beyond the small fact of the matter that she had thrown a knife at his head. Above his head. It was above his head, to help him beat Snakeweed. No matter what Raph said, Leo knew.

He could see that little hint of goodness hidden beneath her dark exterior, the small glint of genuine delight as he had grabbed her hand to stop her reaching for her weapon.

Nobody had believed him at first, of course. And by the time they did... Things just got worse.

And now, he was searching. Scouring the city from his rooftop position, praying silently that he would see her. New York City was big, but not infinite. Eventually, he would find her. Unless you're too late, he thought, bitter yet fearful.

She used to be everywhere. Now, he just hoped she was somewhere.

"Almost there..."

Baxter Stockman flew to a different table in his laboratory, vials clasped in his fingers, for once able to see a benefit in his grotesque fly mutation. He darted from here to there in the room using his wings with much more speed than his old legs could have granted him.

"Almost there..."

When a furious hiss echoed through the room with a sickening bang, Baxter's eyes flicked over to the thick glass cage nearby. The wall that faced him was spattered with blood and venom, with several broken scales gathering in the sticky substance. The mess was stomach-churning, but not as much as the creature creating it. She shrieked and thrashed, slamming herself into the walls of her cell repeatedly. He wondered briefly which of her confines she was trying to break away from.

Carefully, he measured out each of the vials' contents, then paused. He hovered uncertainly, before combining the liquids in a beaker. The mixture fizzed, bubbled, frothed... then settled. The fly-human waited anxiously for a few moments, confirming that nothing was going to explode or catch fire. Once he was certain, he inspected the chemical. It was darker - redder - than the orange substance he had seen before, but he knew that it would work on Karai's unique DNA.

He seized a syringe and filled it with his creation, pride swelling in his chest at his accomplishment, and relief flooding his system with the knowledge that Master Shredder would finally be satisfied with his work. For once, he would not be punished for his failures.

And, on a personal note, once Karai was cured, he would be free to pursue his own retro-mutagen.

Baxter flew to the glass wall, syringe in hand. Karai had apparently given up on her attempt at freedom for now, curled in on herself in the corner of her prison. He pressed a small button on a control pad beside her cage, and a pale blue mist began to seep into the container. Within minutes, the volatile serpent girl was falling unconscious, becoming a slump of scales and flesh on the floor.

"Come on, Karai. Prove my genius..." If he could grin maliciously as a fly, he would have.

Another button on the control pad slid away the glass wall before him, allowing him access to the mutant. He buzzed closer, then pushed the needle into her neck. The sedative had stilled her, so she didn't struggle. He watched as the syringe's contents depleted, flowing into her bloodstream. When it was empty, he removed it, then exited and sealed the cell.

Karai's serpentine body twitched slightly at first, then more violently. She appeared to be convulsing, though he knew she was not conscious. Her scales began to shed, piling up on the ground around her, and her skin soon followed. It was disgusting to observe, yet oddly fascinating. Her body twisted and contorted, reverting back to its original form.

Yet he kept watching calmly. And at last, he saw something other than gross, bloody horror. Karai was sprawled on the ground, a human once more, though Baxter felt strange looking at her unclothed form. However, this had been planned for. He retrieved one of Karai's standard black jumpsuits from a box that had been sent to the lab months ago in case of this scenario.

"Stockman."

The fly-man jolted, still unsure of how a man so heavily armoured could be so silent.

"Master Shredder," he greeted him, for once anticipatory of his boss's arrival. "I have perfected the retro-mutagen for your daughter." Baxter gestured proudly to the cage.

Oroku Saki - the Shredder - stepped closer, staring at his daughter. Memories of the life he had given her, away from the monster that was Hamato Yoshi, rushed through his head, and he smiled beneath his kabuto.

"Karai..." The man stroked the glass that separated him from the girl he called his child, then turned to his servant. "Stockman, bring me her uniform and... release her."

Baxter obeyed, handing the jumpsuit to his master and opening the wall again. The Shredder held the fabric for a moment, before turning to Baxter. "Your presence is no longer required, Stockman."

Recognising the threat between the lines, Baxter attempted a bow and hurriedly left the room, leaving Saki alone with his daughter. He lifted the girl into his arms and examined her, checking for injuries and finding less than he expected. In fact, the worst injuries she had obtained appeared to be from repeatedly slamming herself into the wall in an effort to escape; red welts and bloodied bruises littered her randomly, though thankfully her face wasn't too bad. Traces of her signature make-up were smudged into her skin, and her hair was still sticky with gel.

"Welcome back, my daughter," he sighed, holding her limp form close. He knew she had the blood of his arch-enemy, but she was the last reminder he had of his beloved Tang Shen, and he refused to let go of that memory. Removing the front of his kabuto, he placed a tender kiss on her lips.

Wordlessly, he dressed her and carried her back to her old bedroom.

Thump. Thump. Thump.

Casey Jones lifted his head from the journal in his lap, glancing around quizzically for the source of the noise. Finding an unsurprising lack of things making noise in his bedroom at three A.M, Casey climbed out of bed and left the room, slinging a baseball bat over his shoulder in preparation.

The hallway was empty, with dark shadows shifting over the walls. He listened carefully, then followed the noise down the hall to his sister's room. Resolve steeled, he readied the bat and flung the door open. His fourteen-year-old sister was pacing laps around her room, fiddling with her patchy purple hair worriedly.

"Angel?" Casey balanced the bat against the wall as he closed the door behind him. "What's up, kid?"

Her eyes widened guiltily. "Uhm... nothing, Casey."

He raised an eyebrow. "Then how come you're pacin' round your room this late?"

"I just..." Angel shrugged. "I couldn't sleep."

Casey walked closer to her, placing his hands on her shoulders. "Look... I get it if, y'know, the invasion thing is still messing with your head a bit..."

Angel chewed on her lip. "... I guess, yeah. Something like that."

He wrapped his arms around her, enveloping her in an embrace. "Are you ready to tell me what happened to you yet?"

While his father had been taken to Dimension X with a lot of New York's population during the Kraang invasion, Casey knew that Angel had somehow managed to remain hidden within the city. He suspected she had found at least one ally, but she had yet to mention them.

"I..." She cuddled into him. "I don't know. It's still kinda... weird, like, to think about."

He murmured thoughtfully. "That makes sense. I feel strange thinking about it, too."

"You hid with mutant turtles in a farmhouse," she said with a giggle. "It's obviously gonna be strange to think about."

He put a finger to his lips. "Hey, remember you're not supposed to know that. And anyway, the guys aren't so strange to me now I'm used to 'em. I might introduce you someday."

She beamed up at him. "That'd be really cool!"

"I can't promise that, though," he told her, before adding, "But hey, you can totally meet April someday. She's human - well, mostly."

"Mostly?"

"Long story that I can't explain without permission." He smirked. "Sorry, Angel."

"It's okay." She pulled away from the hug and sat on her bed. "I know some freaky stuff I can't tell you, too."

"Do you now?" he asked, trying to act nonchalant and hide his fierce curiosity.

She nodded confidently. "Mm-hmm. But don't ask, 'kay? I swore not to say anything to anyone about her."

Casey tilted his head. "Her?"

"Nope. No way. Not telling." Angel clambered back under her duvet, smiling cheekily. "I swore that I wouldn't." She pursed her lips thoughtfully. "But I'll ask her if I can tell you next time I see her. If there is a next time..."

"What do you mean if there's a next time?" Casey inquired, kneeling on the edge of her bed.

Angel fidgeted with the duvet. "I haven't seen her in a while. During the invasion, she just... like, vanished. I mean, she did that kinda often, but I could always find her. But one day, she said she had to meet someone, and then... she just never came back."

"Seriously?" He ran a hand through her hair. "That must've been hard on you."

"Suppose so..." She lifted her head to smile at him. "But you guys beat those aliens pretty soon after that, so it wasn't so bad. I just miss her..."

He hugged her again. "I can imagine. After all, I was hiding out in a farmhouse for months missing you."

"I missed you too," she replied honestly. "I'm glad you're back, Case. I'm glad we're all safe now."

"Me too, Angel." Casey petted her head. "Goodnight, kid."

"Goodnight..."

Casey grinned at her as he picked up the bat, turned off the light, and shut the door. Alone in the darkness, Angel allowed herself to frown again. Casey's presence had been soothing, but it hadn't eased her fear. She fretted for her lost ally, wishing she had some way of knowing if her friend was okay.

She waited a few minutes, ensuring that Casey wasn't planning to return, before slipping a hand under her pillow and gripping the item concealed there. When the young girl managed to fall asleep, it was with the slim snake scale curled within the palm of her hand.

Sorry for the shorter chapter, but I didn't wanna stretch things out too much and make it feel forced. Hopefully, chapters will get longer as the story picks up more.

Anyway, thank you for reading, and please review so I know how terrible this surely was :P