A/N.

Here it is… The Big One.

I am about to introduce the biggest plot twist this story has seen, and will see, period. I have seen this idea used in another Fanfiction, and I do know that some people use it, but it's rare. However, about a year and a half ago, my sister suggested we use it, and the idea caught on. We've had lots of fun toying around with this idea, but never had the opportunity to introduce it into one of our stories… until now.

So, this chapter will begin with the blood testing.

And as the story trope goes, that NEVER ends normally.

If you've figured it out, great! If not… buckle up. They are all in for the surprise of their lives. And they'll have no idea how to feel about it.

Also, this chapter has a mention of Avatar: The Last Airbender, which I do not own. My sister and I only recently started watching the show, and we've been loving it so far.

Without further adieu, let's go to the actual chapter! And once you're done, leave a review, favorite, follow, and as always…

Enjoy!

Chapter Ten.
Inherited Genes.
(Karai's POV).
It became very clear that as I expected, I wasn't gonna be much help with anything but the donation.

"Still, thank you for helping me set this all up," April said. "It feels nice to know I'm not alone in all this." She was right. That's been the thought motivating us for the past few hours. We aren't alone. We're all together in this. All three of us have been vigorously preparing for drawing blood, eagerly awaiting to see if we can donate.

"Anytime. Besides, Donnie needs us. This is our best option for healing him." I exclaimed.

Healing him. The words sounded so strange on my tongue. They were filled with hope, but it felt as if they were never meant to be spoken. They never would have had not been for me anyways…

"I know. Casey's idea was a stroke of genius. Donnie says he owes him now." April answered, smiling. I wasn't surprised. To be honest, if this worked, we all owed him. My entire family, that is.

"Speaking of which, we should call Casey and Donnie in here." I said.

"Oh, right! I'll go get them. We'll get started right away." said April. She rushed out of the room, leaving me alone with the equipment. Now my hope was really beginning to rise. We had been given a chance. At last, we had a solution that could free Donnie and bring him back to us. I had never been so grateful in all of my life. Sure, who knows how long it might take, and there's still Shredder to deal with, but the confirmation that Donnie may eventually be good as new was unbelievably reassuring. He would be just fine, I know it.

The door opened, and April and Casey walked in. Donnie was amazingly slung over Casey's shoulder. He didn't seem to be very happy about it, of course, but didn't complain. I couldn't imagine what he must have been feeling at that moment. This test could be the key to a cure.

"Is everyone ready to go?" April asked as she helped Casey lower Donnie into a chair.

"I am." I answered.

"So am I." echoed Casey.

"Can I have a few minutes?" Donnie tentatively asked.

We froze, then turned to look at him. There was no way he couldn't be ready. Seeing our expressions, he seemed to figure out what was going on in our heads, and shifted uncomfortably in his chair. "Don't get me wrong, it's a great idea," he started. "But there are factors of the process that aren't particularly enjoyable, and I thought I would give myself a moment to prepare for the possibility-"

"Oh shoot!" April said suddenly, causing us all to jump. "Donnie, I forgot! I'm so sorry! We don't have to start right away if you don't want to." She said, rushing over to kneel down in front of the chair.

"Why? Is something wrong?" asked Casey.

"No, no, it's just an embarrassing-" Donnie started, but was cut off by April's explanation. "Donnie has a strong dislike of blood."

I raised my eyebrows at my brother. "Really?" I asked.

He sighed, then looked up at us. "You guys know that half-staircase that hangs from the ceiling back at the lair?"

Oh, right. That was where Leo was waiting for me the night that I snuck out, and placed us all into the mess.

"Mikey fell from there when we were six, and hurt his head. That was the first time I had ever seen blood. The whole thing was so horrible, and… well, I passed out. I've hated blood ever since because of that incident. I get dizzy and nauseous because of it. I can't even look at fake blood in movies without my gag reflex going off! Blood phobia is an embarrassing thing to have as a scientist. I'm not proud of it." he finished, blushing bright red.

I didn't even think I could feel worse about the whole thing. Now we were forcing him into a terrifying situation. Why couldn't the universe just give us a break for once?

"That's why I've never seen you go up there?" asked Casey.

"I haven't been up there since that day." Donnie answered. "I'm surprised Mikey still goes up there, but he's fine with it. Me? Never."

"I found out when I stayed at the lair for the first time." said April. Then she blushed. "...I think it's best we don't talk about that at all."

To be honest, I didn't have to use my imagination to hard to figure what happened. Thankfully, Casey didn't press for details. He didn't need to know.

I knelt down next to April and placed my hand on my brother's shoulder. "Hey, it's all going to be okay. You can tell us when you're ready, and we'll make it quick and easy. How does that sound?"

He thought about it for a moment, then nodded. "That sounds okay, thank you." His voice sounded shaky. I desperately hoped it wouldn't go too badly…

Well, it didn't go badly at all, but after Donnie's blood draw, he couldn't stop shaking. I couldn't help but feel even more guilty as Casey and I brought him back to the bedroom and set him down on the bed. Then we took turns going back for our own draws, with me assisting April in hers. Afterwards, April said she would analyze the DNA, and see if anyone of us could donate. I prayed that at least one of us could.

"We might have to wait for a bit." I said as I sat back down with the boys. "She can be pretty fast with it from the look of it, but we could be here for a while."

I settled down on the bed, and looked through my pack. We had plenty of food and water. April and I had taken out the two sleeping bags to use last night, even though we got barley any sleep with her keeping watch on Donnie and me keeping watch on Casey. I still had my tanto, t-phone, and extra bo-staff. Donnie wouldn't be using that for a while, but I had taken it if he needed one just in case.

The photo of my parents. My mother radiated beauty and love for all she saw. I had never known what a mother's love was because of Shredder. I knew she would support me had she been here. Try and help us with anything she could. I wished more than anything that she were here with us right now. I just needed someone to stand with me. Make me feel like I could fix something…

"Hey, what's this?"

I looked over at Casey, who was holding up one more object in the bag. The one I had completely forgotten was with me. "Donnie," I said, taking it gently from Casey, "Look what I brought." I held up the journal for him to see, and his eyes widened in astonishment.

"That's… that's my journal. From when I was a kid!" he said. I nodded. "You left it on your desk in the lab. I'm not exactly sure why I brought it with me. I think I was hoping you might recognize it in case you didn't recognize me."

"Well then, I'm glad I did." he muttered, leaning over for a closer look. Then he looked back up at me. "How much of it did you read?"

"A bit. I skipped around."

He didn't look mad. He simply nodded. "I had to get some frustrations off my chest. Now I regret it."

I shook my head. "No, you had every right to feel those frustrations. I regret my own actions. Now that I know the truth, I can begin working my way towards being a better sister… and learning how to actually be a sister."

"Well, from what I've seen so far, I think you're doing a good job so far." Casey spoke up from where he was sitting.

Donnie smiled. "Me too. And April. And the rest of our family, in time."

At these words, I finally begin to feel some sort of peace. We are on the same side. We are working to restore peace for our family. I start flipping through the journal, looking at everything Donnie had imagined I would be like. The boys adjusted themselves so they're sitting on either side of me. Donnie points out little details about this event or that chronicled on the pages, and we often find ourselves laughing out loud.

"So… how long did you say the marker stayed on?" I struggled to say through fits of laughter.

"A whole week." Donnie answered, chuckling. "It looked so crazy that he covered up his head the whole time, even though he wanted it so badly. And Raph and Mikey had only colored it in halfway, so now Leo was stuck going around with this blue half-done arrow shape on his head!"

The picture on the page proved the whole thing was true. It contained tiny, stick-figure Leo with a small blue smudge on his head, and what looked to be the others and Splinter. Casey was laughing so hard he looked close to crying. "Did you get into trouble with Splinter?"

"I think the arrow on Leo's head was punishment enough. It was pretty scary when he caught us in the act though." Donnie explained. "It didn't help that Raph and Mikey did a bad job at explaining the whole thing. What I remember most was him cutting them off and saying, 'I don't care if you have the perfect heads for it, I don't want any more of you drawing on them!"

All conversation stopped for a full minute as we basically howled in laughter. "I can see where you were coming from," Casey said as the noise died down, wiping tears from his eyes. "Being Airbenders would be a pretty cool career."

"Yeah. We watched the entire show religiously from beginning to end. We loved it so much." Donnie explained.

"I watched it around that time, too. It was really cool. I've even tried incorporating some of those moves into my training." I said. "Maybe April's watched it. We'll have to ask when she's done. And after we get the results."

"She's gonna be sad she missed this conversation." Casey said quietly, but with a smile on his face.

The crazy fits of laughter have worn us out. Slowly, I began to realize just how tired I was. I've been going since yesterday morning. It must have been just after noon right now. My eyelids began drooping, even though my mind protested. Casey and Donnie have been sleeping longer (Donnie much longer than Casey), but they must have been feeling the same way.

"I don't think April will be to happy with us if she comes in here and finds us all asleep while she was working." Casey muttered, yawning. "I technically already did that last night, and I'm not willing to do that again and risk her being mad at me."

Donnie frowned. "Casey, I think we should let Karai get some sleep. She looks tired."

"No, I'm not…" I start, but the 'not' is slurred, much to my dismay. I wanted to stay awake, to be ready when April came in with the results. But the more I tried to deny it in my head, the more I realized that wasn't gonna happen.

"Okay, fine. Wake me up if anything happens, okay?" I asked. They both nodded. "We'll stay awake." Casey said. That was fine with me.

I moved over to one of the pillows, and was amazed at how fast I was pulled into sleep after putting my head down. Within seconds, I was out like a light.

Only to find myself awake again after a very short time. I tossed, and turned, but nothing. I was absolutely restless, despite my being so tired.

'I'm too used to always being on guard anyway.' I thought to myself.

Well, at least if April did discover something, I could be easily roused. Everything would be so much easier if one of us could donate blood for him, but I knew it wasn't that simple. The odds of that were incredibly high. And if one of us couldn't, we would have to find someone who could.

I can imagine that one of our brothers might be able to. But the question was, would they be willing? Would they have no belief in our plan and refuse to cooperate? This was exactly why we couldn't go to them, even despite the fact that it would work best with someone who was related to him, and they were his only biological family.

So that would leave us with no other choice but to go on some sort of wild goose chase, looking for someone who would be able to donate. Which also means trusting a total stranger with our secret.

If such a scenario came true, I was not looking forward to it.

I had quite a while to think to myself while sleep continued to evade me. There was simply too much to think about to relax. The possibility of Donnie's recovery was riding on this plan, this tiny stroke of luck that had been bestowed upon us, but other components could completely derail the entire thing. It was a lot to process, and the test results weren't even ready.

I should just accept that I probably won't get very good sleep for a while. I don't know how long I can go rotating between no sleep and bad sleep, but it'll have to do. Probably none of us will rest until we hear of some improvement. I can just see the coming days filled with exhaustion.

Fed up with lying there and doing nothing, I sat up to find both boys were passed out, too. Casey was sprawled out at the foot of the bed, his arms and legs hanging off either side, and he was snoring, loudly. I have no idea how I missed that. I presume I blocked it out after being lost in thought.

Donnie, on the other hand, was delicately curled into a ball nearer to the pillow. He was snoring softly, too, but whistling even louder. I guess it was the placement of his gap tooth that caused that. I didn't know how heavy of a sleeper he was, and I definitely didn't want to wake him.

Guess I was wrong about the 'none of us' part. I'll change that to 'some of us'. Better.

With nothing better to do, I picked up the journal. The first entry's handwriting was unintelligible, and looked to have been written in a hurry. The ones directly afterward weren't much easier to read, but as I went on, they got a bit better as Donnie's past handwriting improved. They went on for about five years, from the ages five to ten.

What would I have done with my brothers? Who would Miwa have been had I been brought to New York with my father? I closed my eyes and started with everything I knew about their years before I met them, and began to construct something out of a dream. Donnie's imagination. The story that should have been told, but could only be told behind my eyelids.

I would have been the eldest child. I would have protected all of my little brothers with everything I had in me. I would have raised my hand with my brothers when it came time to choose a leader. I would try to win every sparring match, like the four of them. The line between reality and this world began to peacefully blur, as my younger self interacted with the younger versions of my brothers. Acting like we were truly siblings. A real family.

Mikey would come running to me when his dreams because scary. Raph and I would go crazy on the punching bag. Leo and I would give each other advice on how best to handle our blades.

And Donnie… that was simple.

He would have been my friend. Like he is to everyone he knows. My quiet, gentle, peaceful brother with his superior mind, who only took enjoyment in his incredible inventions, who never gave himself enough credit from every wonderful thing he'd done for the family he loved unconditionally.

Just like the brother I had hurt by going after Shredder. Which placed him directly in Shredder's path, and over that mutagen.

"We can get you back," I thought as I pictured my younger self with younger Donnie from his childhood drawing, the one I had no idea he'd done for me on my eight birthday. "Your sissy won't stop until she makes things better..."

BANG!

I jolted awake, the journal still in my lap. How long had I been asleep? I had no idea I even drifted off. Casey and Donnie were also struggling awake around me, and April was at the door, and was once again shouting about a discovery-

The results!

Setting the journal carefully back on the bed, I raced out the door, through the hallways, and into the room that April must have been waiting in for hours. Casey hurried after us, with Donnie haphazardly thrown over his shoulder, evidently not done well, because what I was hearing from behind him was "Watch where you're going!", and "Slow down, Jones!"

"April, what's happening?" I asked as Casey and I helped a very cranky and disgruntled looking Donnie back into the chair. "Can one of us donate?"

April looked pale and bewildered, like she had just had a nasty surprise. I began to dread the answer she was going to give us. This may not be about whether one of us could donate after all. She may have found something wrong within Donnie's DNA. I couldn't imagine things already getting worse on top of everything he was going through-

"No," she said quietly. "None of us can donate."

My heart sank. We would need to track someone down after all.

"But that doesn't matter. There's something you need to see."

That got my attention. My mind was running rampant with all the possibilities of what the heck she could have found wrong in Donnie's blood that could harm him. We pulled Donnie's chair closer to the screen so we could see. I personally had no idea what it was, but maybe Donnie could translate-

And then Donnie went pale. His breath caught. His throat started making unidentifiable squeaking noises, and he looked just as thunderstruck as April.

"What?" asked Casey, voicing the same question on my mind. "What did you find?"

"The mutagen… from the first time he mutated." said April, slowly. I was confused, until she spoke again, much quieter. "It worked in a completely different way than we thought it did. It was so much more powerful than we thought… maybe even more powerful than Donnie or Splinter, even the Kraang knew."

Donnie looked up at me, eyes shiny and teary, and said in the shakiest voice I had ever heard:

"It says there's a match with our DNA."

It made so little sense, that I almost didn't hear him.

"What?" Casey and I asked at the same time.

"A match," Donnie said, breathing heavily and turning back to the screen. "There's a match between me and Karai. She can't donate, but it says that she… she's my…my..."

Sister.

Donnie broke down crying, but he didn't need to finish his sentence for anyone to understand. I was his sister, a half-sister, sure, but his sister all the same. And all this time, I always had been. Biologically.

I felt as if the world had fallen out from under my feet. The shock of the moment had made me go numb. But everything made sense. Father was the last person, the last male human anyways, to come into contact with Donnie and the rest of our brothers. When they mutated, since it was his DNA, he must have unknowingly become their biological father.

But that's never happened in a mutation before, not that we know of. What had happened to make Donnie and the other's mutations different? This shouldn't have been possible at all.

But now wasn't the time to wonder how this happened.

I had to slow down, and figure out what to do.

April had already taken Donnie into her arms and was trying hard to calm him down. The news had caught us all completely off guard, but it seemed to be affecting him the most. He was still in tears, clearly at a loss to explain the situation, and frightened by this new piece of information that had unknowingly had such an impact on his life.

What could I say to that? What could I say to help him? I racked my brain for anything, anything at all, when April beat me to it.

"Master Splinter did tell me once that the place where he got the four of you was… shady," she explained, trying to find the right words. "You four were sold younger than you should have been. And he said that none of you looked well, except maybe Mikey. He was glad to get you out of there when he did. Maybe it was a mix between your age and your immune system's strength."

It wasn't much to go on, and I have no idea where she pulled that out of, but it did the trick. Slowly, we watch his breathing steady, and he began to calm. "How do you know?" he asked.

"I have a feeling… and I'm pretty sure about this one." she said, her gaze cast downwards.

"He never told us it was a bad place." Donnie muttered under his breath.

"Maybe he didn't want to upset you guys." Casey offered.

I knelt down in front of his chair. "Donnie, are you okay?" I asked, genuinely worried. He sniffled quickly, and shrugged. "I don't know."

We were silent for some time, trying to absorb all of this new information at once. It must have been more than Donnie could handle, because within minutes, he was fast asleep. Once April (who still had her arms around him) had confirmed this, we began another conversation in hushed whispers. And this one got our attention.

"If one good thing came out of this," Casey started, "It's the fact that we know someone out there can donate."

April and I both raised our heads at Casey's words, and turned toward him. "What?" I asked.

"Splinter's their real dad because of the mutagen, right?" he asked. When we both nodded, he continued, "That means that there must have been another employee there working when they were born, for it to work. A lady. If no-one from Splinter's side can donate…"

"Maybe she can!" I said. "His biological mother."

"That could work," started April, "But how on earth are we supposed to find her?! She could literally be anyone! Besides, if we did find her, we would have to bring her here. She may have a family of her own, and a job that she can't leave, and she's just an innocent women. We'll be turning her whole life upside-down!"

"She's Donnie's best chance. And we need all the help we can get." Said Casey. "We can find that pet-store, figure out who was working there the day Splinter went to get the turtles, and then track her down afterwards."

"What if she freaks out because he's a mutant?" April asked. I was uncomfortable with the situation too. Here we were, about to purposely break Father's rule that my brothers could never be seen.

"Then we'll just have to deal with it. I'm sure we can think of something." Casey said.

I shook my head. "Casey, think about this for a minute. She's his mother, his blood. What do we do about that? We can't just tell her that and drag her into this! Donnie would agree if he were awake, I know it."

"We don't have to tell her." He answered. "It's cold, I know… listen, why don't we worry about finding her first? Then we'll go from there once we have all the info we need. April, do you think you and Donnie can hack in and find more information about that place?"

"Sure. That's a place to start, at least." she said. "Let's wait until Donnie wakes up though. I don't think he's gonna be very happy about the plan, and being short on sleep won't help."

"Perfect. We can talk about it with him then. April, why don't you stay with him? I want to talk with Karai for a moment."

Good. I needed someone to really talk to anyways.

Casey and I stood and left the room, with me quietly closing the door. My hand lingered on the doorknob for a moment.

"Karai? Are you okay?"

I nodded. "Yeah. I just needed to clear my head, that's all."

I really did. It a matter of minutes, those results caused everything to change at once. It was all so much to take in. Nothing would ever be the same, or go back to the way they were.

"I didn't even think… when I thought of the plan… we would find something else-"

"Your plan is still brilliant, Casey." I said, cutting him off mid-sentence. "And you are right, it's all we've got. We know this lady can donate, and that means she can save my brother. This whole mess is confusing, and stressful, but I think we should go for it, and see what happens then. And if it doesn't work, we'll figure something out."

"Are you sure?" he asked. I closed my eyes and took a breath. This was it. Ride or die.

"Positive."

A/N.
… I think I might need to clear some things up.

I wrote the first Author's Note before I wrote the actual chapter, and I fear I did a bad job at explaining.

The turtles, in this universe, were irresponsibly sold just hours after their birth. The place where Splinter bought them from was a pretty gross place, and they weren't in the best of health. The fact that they were under 24 hours old, plus the fact that their immune systems weren't the best, were the two key factors that lead to the complete DNA re-write. This kind of mutation must be incredibly rare, since such a situation is incredibly rare. Therefore, the turtles became biologically related to both Splinter, and one of the ladies working there the day they were born.

I'm sorry if this all seemed completely out of the blue and random. I was hoping to take people by surprise, like in the story. I don't wish to lose any readers because of the plot twist. The idea didn't even occur to me until now.

I'm also sorry if the writing looks rushed. This chapter was difficult to write, and if the characters are confused, half the time I'm confused on how to move the story along.

The next chapter is also a key chapter in the story, but not as important as this one. It will deal with them finding out who the mystery woman is, and then paying her a visit… both of which will be very interesting.

I'm very excited about bringing her into the story. My sister and I have been developing her character for a little over a year and a half, and she's absolutely wonderful. But will she help them?

We'll have to wait for the next chapter to find out.

Anyways, that's it for this chapter. I hope everyone enjoyed this, and once you're done, leave a review, favorite, follow, and as always…

Stay tuned! ;)