A/N: Here is a new, edited version of chapter 1! Chapter two's update will be coming soon. Feel free to skim over the introduction to the characters. I wrote that mainly for my friends who don't watch the show.

Chapter 1

"Home sweet home!" yelled 15-year-old Michelangelo as he burst through the doors to the home. He was only one of the quadruplets. His three brothers, Leonardo, Raphael and Donatello followed close behind.

"It is good to be home." Donatello agreed, heading for his computer.

You may think that the boys were normal teenagers, but they weren't. They were mutant turtles, raised by Splinter, a mutant rat. Splinter taught them Ninjitsu. Each turtle wore a different coloured bandana and carried a weapon of choice.

Leonardo (Leo) wore a blue bandana and carried twin katanas. He was the unofficial leader of the boys. Leo was quick thinking in emergencies. He was the sober type and took Ninjitsu very seriously.

Raphael (Raph) wore a red bandana and carried twin sai blades. Raph was very hot-headed. His temper sometimes got out of control. Most of the time he tried to control it.

Donatello (Donny or Don) wore a purple bandana and carried a Bo staff. Don was the brainiac of the group. He was constantly working on new inventions. He could fix any machine.

Michelangelo (Mikey or Mike) wore an orange bandana and carried two numchuks. Mike was the wise guy. He had a pun or wisecrack for everything.

"Hey guys, where's Splinter?" Raph asked, looking around.

"I don't know, but he's not here." Leo replied, after checking Splinter's room.

"Maybe he went out to look for us." Mike suggested.

They decided to wait a while for him to return. If he didn't return before dawn, they would start scouring the city for him. During this time waiting, Raph was even more short-tempered, for he wanted to go look for Splinter now. Leo kept to himself, making plans and Don worked on his inventions. Even Mikey was quiet.

The clock chimed midnight.

"We should turn in guys." Mike yawned. The others immediately stopped and gaped at him. "What?" he asked.

"You want to go to bed Mikey?" gasped Don. Usually Mike liked to stay up as late as possible.

"Ya feelin' alright?" Raph placed his hand on Mike's forehead.

"I'm worried about Splinter." Mike confessed sadly, pushing away Raph's hand.

"We all are, Mikey, but for once you're right. You all should turn in. I'll stay up a while more just in case he comes home." Leo decided. The four said goodnight and Raph, Mike and Don headed reluctantly up to their rooms. Leo turned off the lights.

He didn't have long to wait. Shortly after the three had gone to bed, someone opened a hidden door near the kitchen. Nearly completely silently, it crept through the home, yet Leo heard it. He could tell by the sound of the footsteps that it definitely was not Splinter.

Donny had left his Bo staff by the couch where Leo was, so Leo picked it up and headed in the direction of the footsteps. The person was headed towards Splinter's room. When he was close enough, he jumped on whoever it was and pinned them to the ground with the Bo. A loud bang activated the clapper lights. Leo gasped.

He was staring into the brown eyes of another turtle, like he and his brothers. A magenta bandanna framed the surprised eyes. She looked a little annoyed (and maybe scared) that she had been seen.

"Who are you?" he asked.

"I'll tell you if you get off, Leonardo," She groaned.

"Sorry." He apologized as he got off and helped her to her feet. Her bandanna hung like pigtails and came only to her shoulders. Now that she was standing, Leo could see that she was a little shorter than he was. "How do you know my name?"

"I've always known your name." she replied. "I know I owe you an explanation. I don't want to wake the others, so please, follow me." She hurried off and Leo dashed after her. The blue-masked turtle watched in awe as she entered a doorway - which he knew wasn't there before when the four arrived home - by the kitchen. She flicked a light switch and turned to face him.

"Leonardo, I--"she began.

"Please, call me Leo." He corrected her.

"Leo, I'm your sister. My name is Cassiopeia. I know that it's a bit of a mouthful so just call me Cassi. I was raised away from you and the others. I don't know why. Master Splinter just said we would meet one day, when we were ready."

A voice from the door interrupted them.

"Who are you?" Don asked, staring with shocked eyes at Cassi.

"Don, this--"Leo was cut off.

"Who's the babe?" Raph was leaning against the doorway.

"Raph, Cassi is--" He turned back to Cassi. Leo was cut off once more.

"Got a girlfriend, bro?" Leo didn't need to turn around to know who was behind him. Cassi smiled warmly at the other three and walked over to them. There was recognition in her eyes, and Leo guessed that she already knew who they were as well.

"Donatello, Raphael and Michelangelo. It's great to finally meet you. I've waited a long time for this day. I'm Cassiopeia, your sister."

Mike groaned. "Why? Why our sister?"

Cassi ignored him and continued. "Just call me Cassi."

"We don' need no baby sis to carry 'round and protect!" snapped Raph. Cassi's eyes blazed with anger.

"I'm fifteen too, Raphael! I don't need protecting with this beauty!" With that, she pulled out the sword that was strapped to her shell. Electricity bolts flared madly around it. The boys backed up. None of them could believe their eyes.

"The Sword of Tengu!" gasped the four together.

"But, we blew that up, didn't we?" asked Mike.

"Yeah, you did." She nodded. "This is a copy I made. It works even better than the real one." There was a hint of pride in her voice.

"You made it?" Don asked in shock.

"Yep!" she said as she put it away. Her smile faded. "Have you guys seen Splinter lately? He usually comes to train me at night, but he never came tonight. I was going to get him when Leo jumped me."

"Sorry about that." He apologized. "No. He wasn't at our place." Leo told her. Concern and anger flashed in her eyes.

"We can't just sit here then! We have to find him!" Cassi half-shouted.

"My feelin's exactly!" Raph agreed.

Mikey spoke up. "We've been out all day. I'm tired. We're tired. We won't be much help if we're asleep. Can we pick this up in the morning?" After he finished, he looked just as surprised as everyone else did that he had said that.

Cassi sighed and her eyes cooled off. "You're right. You guys go back to bed. I'll meet you in the morning. If I recall right, that was your plan anyways."