After returning from the docks Donnie decided to analyze the sample of Karai's scales they had found on the sidewalk to see if it could tell him why she can change form, what he found was exactly what he feared. He got back to work immediately on the Retro-Mutagen but now the others were starting to grow concerned, it had been three days and he had hardly moved from his make-shift lab.
"Donnie it's late, get some sleep" Leo said, entering the kitchen of the restaurant where as usual Donnie was hunched over a microscope at his table.
"I will, in a little while. I'm almost done" Donnie replied without even looking up
"You've been saying that all day" Leo was clearly getting annoyed with his brother, he admired his persistence but for now enough is enough.
"I know but I'm so close and I have to finish this soon"
Leo grinned slightly, understanding his brother's desire to finish the Retro-Mutagen as quickly as possible, but he also understood that Donnie had barely been sleeping since they found Karai. It wasn't until Donnie felt Leo's three fingered hand on his shoulder that he finally looked up.
"Leo I swear, I'm so close. At this rate I'll have done before tomorrow" Leo's heart skipped a beat when he heard that, Donnie never gave out a time frame for when he'd finish something unless he knew he was on the last step.
"I want to save Karai too, as soon as we can. But you need to sleep, and she can wait a few more hours" Leo said in a calm voice, briefly his mind went back to when Karai had been locked up by Shredder, he had hated knowing that Mikey needed help more than she did in that moment. Now he understood that Donnie had barely slept in three days and didn't have to be reminded that Karai can handle herself, when did he get so mature?
Donnie however let out a sigh
"Look I didn't want to tell you this but I analyzed the scales we found on the sidewalk, it's bad Leo" the genius turtle shamefully admitted.
Forget skipping a beat, Leo felt his heart stop. Bad? What does he mean bad? How bad could whatever he found be?
"What?" Leo tried to ask but that was all he could get out, his body was filling with an unfamiliar sense of fear. It felt like the fear he had when he found out Splinter had been left behind, possibly dead, when they left the city. A fear of the unknown fate of someone he loves, only worse because he knows that Karai is alive, so what if they can't help her?
"Remember when I said she was becoming more snake like by the hour?" Donnie questioned and got nothing more than a nod from his older brother. "Well that's a little more true than I realized. Her DNA contains a hint of a complex chemical formula, almost identical to Retro-Mutagen, which is why she can change her form" Donnie began to explain.
"Hang on, if she's been exposed to Retro-Mutagen then shouldn't she be completely human again? And how did she get anywhere near Retro-Mutagen in the first place?" Leo questioned, knowing very well that Donnie is the only person to be able to create Retro-Mutagen.
"Like I said it's almost identical to Retro-Mutagen, it's missing April's DNA. I'm thinking that Stockman must be trying to create his own Retro-Mutagen, and accidentally spilt some into the vat Karai was mutated with. The problem is it made her DNA unstable, half her DNA is diminishing. The human half" Donnie sadly admitted
"So you're saying that… she… she could, will" Leo began to stutter as he tried to process what it was that he had just been told.
"I'm saying that if we don't act soon she could be beyond help. So far the deterioration of her human half appears to have been relatively slow, considering it's been almost five months since her mutation and she's only missing about thirty percent of it but because her DNA is unstable it could speed up or slow down at any time" Donnie explained but Leo appeared to be thinking hard about something.
"Say you do finish it by tomorrow. Say you finish it and we go out tomorrow, find her and change her back. What happens to that thirty percent?" Leo questioned, unsure if changing Karai back would still be a good idea if it meant she may have some serious problems afterwards.
"That's the good news. Stockman's flawed Retro-Mutagen doesn't destroy the DNA it attacks, rather it stores it away somewhere, like how some diseases can be carried without the host getting sick" Donnie explained, prompting Leo to let out a sigh of relief.
"So she'll be ok?" The older turtle asked
"If we help her in time, if the snake fully takes over it won't be as simple as spraying her with Retro-Mutagen" Donnie explained and Leo nodded thankfully.
"If you don't finish by midnight wait until morning" Leo instructed, glancing at the clock to see that it was just past eleven.
"Fair enough" Donnie agreed before returning to his work.
So Donnie did finish, around two-thirty a.m.. He knew Leo and the others were worried about him but he just couldn't stop, he was getting closer and closer and finally it was done. Raph, Casey, and April left early in the morning on another scouting trip and weren't there when Donnie woke up and told those still in the new lair about the Retro-Mutagen.
"Well then what are we waiting for dudes?" Mikey questioned excitedly "let's go get Karai!" He exclaimed even more excitedly.
Donnie handed Leo the spray bottle of Retro-Mutagen
"I'm going to sit this one out if you don't mind, I didn't get to sleep till almost three" he admitted sheepishly rubbing the back of his neck.
Leo nodded with an 'I told you so' smirk but said nothing to Donnie
"Be safe my sons" Splinter warned before Leo and Mikey could set out
"Don't worry Sensei. We'll be fine and we'll bring Miwa home" Leo promised, not even realizing he had used her original name until he said it.
"So where we going?" Mikey asked as the two brothers moved stealthily through the Kraang infested city.
"She pointed east and said comet when we were at the docks, I think she was giving us a clue on where to find her" Leo answered before stoping in front of a rather large building.
"And this place is?" Mikey questioned as Leo forced open the door, noticing that it didn't look like he was the first one to do so.
"The planetarium"
The two walked into the large building and Mikey was immediately filled with a sense of awe. Once you passed the front desk the building was one large room with rows and rows of chairs going in a circle all around it. The walls were painted black so the holographic projections of the solar system could be displayed and they could give the illusion of outer space, and with no power it would be near impossible to see if it weren't for the white dome of the ceiling and few emergency lights.
"Karai, it's Leo and Mikey! Are you here?" Leo shouted as he started walking around the large room. "Donnie finished his Retro-Mutagen, we're here to help you!" He continued to shout.
As they walked Mikey knew he heard something, he couldn't pinpoint where it came from exactly but he knew he heard it.
"I know you're here Karai, I can hear you slithering!" He shouted as he scanned the rows of chairs.
Leo listened carefully, and he heard it too. He turned in the direction he thought the sound was coming from, only to be met with Karai lunging at him.
She coiled her tail around him, the way she had coiled her tail around Splinter when she was first mutated. This frightened Leo because although it didn't take much to snap her out of it then she had still done it, and now her mind was even farther gone.
"Karai.. listen.. it's me.. Leo" Leo pleaded with her as he struggled in her grip for oxygen.
She looked at him hungrily, not remembering who he was as she continuously tightened her grip on him.
"Karai…. stop, please" Leo struggled as she continued crushing the life out of him, though she was holding back. He could sense that she wasn't using all her strength, if she really wanted to she could've killed him by now.
Suddenly a throwing star came flying from across the room and hit the side of Karai's tale. Hissing at the contact Karai whipped around to find Mikey running away. Instantly she released Leo and chased after the younger turtle who ran throughout the planetarium until Karai had him backed into a corner. She loomed over him and was about to strike when he took her by surprise and jumped onto her. He wrapped his arms tightly around her neck and his legs around her waist, she thrashed about and pulled at him with her tale but it only made him hold tighter.
"Karai stop, it's us, your brothers. We can help you, we can change you back. Then we can all go home, Splinter's been worried sick about you" Mikey said softly into her ear, or at least the place where it should've been. She continued trying to throw him off her but began to calm at the mention of her father.
"It's time to go home Karai, we're not leaving without you, not this time" Mikey quietly promised, now Karai was almost perfectly still.
Deciding that she was calm enough Mikey jumped off her as Leo came over, the spray bottle in his hands.
"Hold still Karai" the blue banded turtle instructed before spraying her.
When the orange chemical came into contact with her scales Karai let out a loud hiss. It felt like water but it made her entire body go numb. Against her will she transformed into her human form before her mind began to cloud over and she was so focused on that that she didn't even feel it when her fangs morphed back into human teeth and her eyes once again let color enter her vision.
Leo and Mikey watched as Karai changed into her human form like they had seen her do before but this time, much to their relief, the scales on her face were replaced by human skin and when she picked up her head and opened her eyes they saw two golden orbs staring back at them.
"Ugh, what happened?" She asked as she started picking herself up off the ground
Leo went over and helped her to her feet
"You don't remember?" He questioned but it didn't really surprise him, Mr. O'Neil didn't remember anything after being changed back.
"Bits and pieces" Karai answered, slowly removing her hand from her head as a headache began to subside.
"How do you feel?" Mikey asked
"Like I never want to touch another snake again" she answered.
Mikey and Leo chuckled at their sister's response and once she processed what exactly had happened Karai smiled too.
Like always they moved underground to get back to the pizzeria but when Leo began climbing up the ladder to the hole in the kitchen floor with Mikey right behind him, they both glanced back to see Karai wasn't following. Instead she was just standing at the base with her arms wrapped around herself staring at the ground, like she was in a trance.
"Karai, you coming?" Mikey asked but when she didn't answer he jumped down and Leo did the same.
"Karai what's wrong?" Leo questioned as he tried to get a look at her face
"Nothing" she said, snapping her head up, but it was all too evident that she was lying.
Tears were watering in her eyes, threatening to spill. Her voice hadn't cracked yet but her face was growing red with the effort it took to keep herself from crying.
"Karai" Leo said again, she took a deep and shaky breath before her tears fell onto her cheeks.
"I can't face father" she whispered, her voice so low Leo almost asked her to repeat herself.
Leo wanted to say something, he wanted to tell her that she had no reason to worry, but he didn't know how. Fortunately Mikey did.
"That's crazy. All he wants is to see you, he understands you were mad at Shredder, he just wants you home Karai. We all do" Mikey said, not really sure if his words would be helpful.
But Karai smiled gratefully as she wiped away her tears "ok" she agreed, she would come.
Upon entering through the hole they found that not even Donnie was in the kitchen
"Just a warning, this place is a lot smaller than the lair" Leo said
"anything beats the street" Karai said back and Leo chuckled, almost envying how quickly she had regained her composure.
The three of them entered the main room and instantly it fell silent. Donnie, April, and Casey were sitting on the couch watching TV with Raph on the floor at their feet and Splinter was in his usual spot peering between the boards on the window, all five turned to look at the three.
"Miwa" Splinter said, he knew his sons would bring her home for good this time but he couldn't help it. No matter how many times they had been separated being reunited would always seem unreal to him.
He was the first to approach them, his eyes locked on Karai who was so sorry for running off that when she saw her father her confidence faded and she could only stare at the floor.
"Father I-" she began to explain but that was all she had time to say before Splinter grabbed her shoulder and pulled her into a hug.
For a brief second Karai was taken back by this but she soon returned the hug, burying her face in the fabric of Splinter's robe.
"I'm sorry" she muttered as Splinter rubbed her back gently
"Apology accepted" he said to her.
When they went to sleep that night it was the same as every other night, the teenagers forced Splinter to take the couch and once that was accomplished they all spread themselves out on the floor. April was sleeping under the counter, after waking up the first morning to find that Casey had accidentally put his arm around her in his sleep, and Karai also claimed a spot behind the counter. It was late at night and unsurprisingly Karai couldn't sleep, she glanced around the room and from where she was she could see Mikey's open eyes staring up at the ceiling.
"Anyone else awake?" She asked in a loud whisper after a moment of hesitation, there was something she had been meaning to ask Mikey but she didn't want the others hearing.
"I am" Mikey's whispered voice responded but no one else did, perfect.
"Did you mean what you said?" She questioned, Mikey only turned his head and looked at her confused
"huh?" He asked, oblivious to what she was talking about.
"I don't remember a lot but I remember the warehouse, and the planetarium. You called yourself my brother" she reminded him and she watched for his reaction.
He was lying on his back with his arms folded behind his head but he still made a shrugging motion.
"Well yeah, I mean I know Leo, Raph, Donnie, and me are adopted but we still have the same dad right?" He asked her, as if it were just now dawning on him that he was the only one who considered her a sister. "And I bet that you know if she was still alive we'd have the same mom too" Mikey continued.
Karai smiled, she figured if her mother were still alive than none of this would be happening but maybe Mikey's right, maybe somehow the turtles and Splinter still would've found each other.
"I don't know, what do you think?" Mikey questioned and Karai smiled sweetly as she looked up at the ceiling.
"I think that having brothers is going to take some getting used to" she said, a wide grin braking out across Mikey's face.
They spent the next hour or so talking, mostly it was Mikey telling Karai all of the stupid things the boys had done over the years and Karai laughing at the stories. After awhile Raph woke up and told Mikey that he was telling a story wrong then proceeded to tell it himself. This was soon fallowed by April and Leo waking up at almost the exact same time, not long after Splinter woke and then Donnie, Casey eventually woke when Mikey got a little overexcited and decided to wake the hockey player by tossing Ice Cream Kitty onto his face.
"WHAT THE? MIKEY!" Casey exclaimed, throwing the cat off his face and springing to his feet, chasing Mikey around the small room with the others all laughing.
That night no one cared. No one cared about the war going on outside the restaurant's walls, no one cared that they had all lost so much, Donnie didn't care that the most sleep he had gotten in the last four days accumulated to a total of six and a half hours, Karai didn't care that her memory of the past five months was next to nothing, and Splinter didn't care that none of his children would sleep or even keep quiet. That night all anybody cared about was holding onto the first feeling of true happiness that they had felt in a long time.