A/N.
Hi everyone!
Thank you all so much for the reviews! They were all so kind. This is definitely not a one-shot, so be prepared for more. Things get even crazier in this chapter. Now, once you're done, leave a review, favorite, follow, and as always…

Enjoy!

Chapter Two
Slipping Apart
(Casey's POV)
I got going the second I received the text from Raph.

My dad was going to kill me for running off again, but it didn't matter. I left a quick note for him and my sister, telling them that one of my friends had been seriously injured and was missing, but told them not to do anything about it, and that I would handle it. Hopefully, they'll understand, but it's not the time to dwell on that right now. I could barely wrap my mind around the news I had received.

Donnie was mutated. It was mind-blowing. We had witnessed plenty of mutations before...but never thought about what would happen if one of the turtles got a secondary mutation. What's even worse, we had no idea how to cure Donnie! He was the only one who knew how to deal with this kind of situation, but now he's gone, and we're out of options. I dashed into the lair, expecting to see everyone. But to my surprise, there was only one person in the room. And she was sleeping on the couch.

Karai.

She was the one who had witnessed the mutation up close. The poor girl must have been traumatized. I went over and sat down next to her, careful not to startle her. She's already been through enough. While I waited, I looked over her features. All the makeup had washed clean from her face, so I could see her almond-shaped eyes and pink lips perfectly. She was pretty. As a matter in fact, I dare say, pretty as April. I gazed down at her for a while, before I noticed a shadow beginning to loom over us.

I turned around to see Raph. But this was the angriest I had ever seen him. Fire literally burned in his green eyes. He was beginning to raise his fist, before I threw my arms up. "Raph, stop!" I shouted. Raph blinked, and then stared at me for a second. "Did you not know I was here?" I asked. He didn't answer, but the silence told me yes. Then, I realized why he had come out here. What I had just caught him about to do. "You...you weren't gonna...hurt Karai, were you?!" I asked.

"She deserved it!" Raph silently spat back. "She deserved it after what she caused!" I was in shock. "Dude...your own sister…"

That did it. I screamed as Raph came flying at me. He landed a few feet away, coming to the ground with a thud. It's also what got everyone up. They ran into the room, shocked to see Raph lying on the ground. Karai was just sitting there, staring off into the distance. Raph was panting. "Raph, what's going on out here?!" asked Leo. Raph turned to Leo, fire still burning in his irises, and literally screamed his next sentence.

"SHE'S NO SISTER OF MINE!" he yelled, then he charged off to his room. We heard the door slam, and a bit of dust rained down from to ceiling. Karai sighed and closed her eyes. She was clearly hurt, but she was trying to be calm. Raph's words however, stung her greatly.

I sat down next to her. "Don't even think about believing what he said. Raph's just in pain. We all are." Mikey nodded. "You're right, Casey. Are we really gonna let this bring us down?" He turned to Leo and Splinter, who hadn't left the room yet. "Are we?" he asked again. Leo sighed and hung his head. "Mikey….." then he left the room without another word. I jumped up again. "How could you just give up like that?!" I screamed. "It's not like he's dead or something! So stop acting like he is!"

Suddenly, we heard footsteps. Running footsteps. Then moans and wails echoed through the tunnel. The voice sounded familiar. I gasped. I knew who was coming. And I definitely wasn't prepared to see just how broken April's face was.

The poor redhead's eyes were bright red and puffy, her cheeks were soaked, and she was making strangled noises like a wounded animal. Her father, Kirby O'Neil, came running right after her. She must have run right out of their apartment and all the way here, and he went after her, scared that something was wrong. Well, something was definitely wrong, so he had a right to do that.

"April! How did you even hear about this?!" I asked. "I texted her." said Raph, who had silently come back into the room. "And don't believe Casey! It was Karai's fault!" I turned to April. "April, please. I'm begging you! She didn't have anything to do with it! Donnie sacrificed himself to save her!" I said. "Liar!" shouted Raph. "You're just trying to defend her because you think she's cool or something! Get your head out of the clouds and back into reality!" I stood. "You just want someone to blame for everything! I'm honestly amazed that you're not blaming yourself like Leo is!" Raph's face went red with anger, then he marched up to me. "If she hadn't run off, none of this would have happened! She led us all into his trap! She led Donnie right to the mutagen!" My face went red with anger now. "It was an accident! She didn't see that coming, none of us did! And if you can't accept that, and just always put her to blame, how good does that make you?! How does it make everyone else feel?! HOW DOES IT HELP DONNIE?!"

"ENOUGH!"

I had never, ever, heard such an infuriated voice. The cane slammed down so hard that we all jumped in shock. Splinter was panting with rage. We all instantly went pale. When I looked at the boys, they had all slightly moved closer together. I realized that for the first time in their lives, they were actually scared of their own father! Splinter saw this and instantly a look of horror crossed his face, realizing what he had just done. April's father hugged her closer. April hadn't stopped crying, but she was very quiet now. Karai was just frozen to the couch, like she had been the entire time. Kind of like me.

Ears drooping, head hung in shame and sadness, Splinter was turning away to retreat back to the dojo, when Karai bolted from the couch and caught his arm. "I love you father!" she desperately screamed. Splinter turned to face his only daughter. Karai began to cry again, softly. "I never wanted this to happen!" she said. "I'll do anything to make this right. Do it over again." Splinter pulled his daughter close. "I love you too Miwa." he muttered. "But nothing can replace your brother." With that, he was gone again, back in the dojo for who knows how long.

(Karai's POV)
April and Casey stayed the night. April's father went back to their home. I didn't sleep for the rest of the night. I don't think anyone did.

About an hour after Casey and April arrived, I got up. I couldn't stay sitting anymore. Maybe I could walk around a bit to keep my mind off of everything. But even that led back to what had happened, because I found myself at the metal doors of a room that I hadn't entered yet.

The lab. Donnie's lab.

And I somehow got the willpower to push those doors open.

There wasn't much in it. There were science-y posters all over the walls, and a bunch of lab equipment. I walked over to the desk. It had a computer (which looked like it had been built entirely by Donnie), a few papers and pencils, some beakers and test tubes, and a journal. The journal looked old, more than ten years old. Curious, I picked it up and opened it to the middle of the book. It had a child's handwriting. But that's not what shocked me. It was the contents of the journal that did.

March 23rd.
Today I had fun playing with Miwa. She and I played hide-and-seek! I found her up in the tree. She can climb really fast. Then after we ate lunch, we got to go into the lab and look at a new dictionary I got a few weeks ago. Miwa likes that it's white. White is her favorite color. I really wish she was here.

I couldn't believe it. Donnie had written this what he was a child! He had imagined that I had been there with them! I flipped through the book again.

May 18th.
Today is Miwa's birthday! She would be eight years old. I won't be seven until September 29th. That's my mutation day, you know. I gave her a drawing for her birthday. She loved it! She says that she wishes she could give one to me. Miwa likes drawings.

Underneath those sentences was a picture of a stick figure turtle and a stick figure girl with long black hair and light orange eyes, which he must have used to substitute for my amber eyes. They were both smiling and chasing each other around the room, which I recognized as the living room of the lair. I flipped through more pages, seeing more and more of these little strands of sentences involving the adventures of Donnie and imaginary Miwa, until I came to one that shook me to the core. It was recent, and no longer had a child's handwriting. And I remember the date like yesterday.

November 22nd.
I found out who the real Miwa is today. And she just so happens to be our enemy. I'm pretty sure my childhood was ruined.

I sat shocked. I looked at the next one.

December 3rd.
Karai decided to try and let Tiger Claw into our lair. But she also found out the truth. She ended up getting taken back by Tiger Claw. Leo wants to go after her, but I'm still not sure I can trust her.

The last one has yesterday's date. I could barely read it. Especially at the end.

December 10th.
We finally got Karai back today. She's settling in. But I'm not settled at all. When she came out of the dojo after spending some time with Sensei, she had a look in her eyes. Like she was plotting something. I'll keep an eye on her.

Edit: Does this really end tonight?

Once again, I found myself starting to cry as I remembered what I had said before foolishly running off to face the Shredder. "This ends tonight!" I can't even believe that I unknowingly hadn't said that about Shredder's fate...I had said it about Donnie's fate. Had he known? Had he known that he wasn't coming back, one way or another? Wherever Donnie was right now, he must hate me. I deserve it. But what good would that do?

Father was right. No one could replace Donnie. If he wasn't found, our family could fall apart. And I had just found them. I'm not about to lose anyone. Especially not one of my brothers. Not on my life.

And so, in that moment, I figured out what I was going to do.

I grabbed a bag, and put in what was necessary. Two sleeping bags, food, water, a t-phone. I sheathed my tanto, and slung a bo staff over my shoulder. I also took the journal, and a picture of my parents, before the beast I once called father set our cruel path of fate into motion. Hopefully, my family will understand my actions. I looked around the lab one final time, then slid the doors shut. The sense of warmth that had settled around me was gone now, with the rest of the lair being surprisingly cold. I snuck across the living room, and was just about to leave when a voice stopped me.

"You're going to find him, aren't you?" I froze, then turned to find Casey. He looked scared. I sighed. "Well, number one, you didn't make it very specific. Second, I did tell father that I was going make this right." Casey looked up at me with worry. "Karai, you don't have to do this all by yourself. We're with you, and sooner or later, someone's gonna make a plan. Stay with us." He held out his hand. "Stay with me."

I did a double take at his words. Then, I sighed again and pulled out my t-phone. "Give me your cell phone number." Casey quickly pulled out his phone and we exchanged numbers. "I'll keep in touch as much as I can." I said. "Keep them safe." Then without even thinking, I rushed forwards and hugged him. He seemed startled at the sudden embrace, then wrapped his arms around me. "I won't tell anyone about this." he said. I nodded. "Good." I started up the steps, then turned once more. "Goodbye Casey. I'll see you soon."

Then, without looking back, I stepped from the lair, and headed for the surface.

A/N.
Once again, thank you all so much for being here and reading this! Next chapter is really gonna bring on some excitement. Both clans will find out about a certain kunoichi's leave from the city, and she'll make a visit to an unlikely location. Will she find Donnie there or not?

Now, once you're done, leave a review, favorite, follow, and as always…

Stay tuned! ;)