Disclaimer: I do not own the TMNT.

Don noticed arcs of electrical energy surging from his lab. "Guys, get down!" He shouted. Karai overheard him and ducked behind a wall. Mikey, Raph, and Don huddled low behind the stairs. A white wash from the surge blinded everyone.

Mikey blinked away the flash and quickly scrambled over to the lab. Don shook his head and stood up he rubbed his forehead. Raph noticed Mikey headed towards the lab. "Mikey! Wait up bro!"

Mikey wobbled into the lab and dropped onto his knees next to Leo and Shredder. Both were panting, had open sores on their skin, and had steam drifting from the sores. Leo drew in a wracking breath and tried sitting up. Shredder groaned and turned onto his front. Mikey crawled over to Shredder. "Leo? Is it you?" He whispered. "Michelangelo…" Leonardo rasped.

"Shutup, you're not my brother!" Mikey shouted at him, he clenched his hands into fists. Leo gave Mikey a shocked look. "M-Mikey, please…" He began. Mikey glared at him. Shredder looked down to see his stump of a right arm. Mikey sent a punch to Leo's face with tears collecting in his eyes. "Shut up!"

Leo's head smacked into the ground, he groaned and turned onto his plastron. "Mikey… it's me… please… you've got to believe me…" Leo whispered.

Mikey shook his head violently. "No, you're not Leo. You-YOU! You killed Master Splinter! You dropped his ashes on purpose!" Mikey sobbed. Leo's eyes went wide. "No…" He whispered, tears blurring his vision. "No..." He repeated. Leo turned a glare onto Shredder. "You bastard!" Leo growled at him. He trembled.

Don and Raph entered the lab then. Leo struggled to get up, he was ready to rip Shredder's throat out. Raph planted a foot on his shell, Leo's plastron hit the floor again. "So what the hell is goin' on 'round here?" Raph asked, glaring down at Leo. Mikey pointed at Leo. "He's Shredder, this is Leo… It's confusing but true." Mikey said.

Leo struggled weakly under Raph's foot. "Guys, please…"

Don rubbed his chin, still not totally convinced. Leo looked over his shoulder at them. "You have to believe me! I can't go another day having you guys think I'm Shredder, when he's right under your nose and ready to kill you! I can't live with it anymore! If you don't believe me, kill us both, at least then you'll be safe!" Leo snapped angrily, trembling still.

Raph and Don exchanged glances.

"You'd like that, wouldn't you?" Mikey whispered, standing up from beside Shredder. "Mikey, what're ya," Raph began, stepping forward. "Raph, don't you see? Leo… That thing," Mikey shouted," is trying to take Leo away from us! He can't kill us all, so he's trying to take our brother with him!"

Don stared at him suspiciously while rubbing his chin. "Mikey, I don't know about that one… It sounds very… I don't know…"

Raph nodded in agreement with Mikey. "Donnie, I think the knucklehead's right. This thing is trying to play us like usual. And didn't he try to kill Mike?"

Leo shook his head and slammed his fist on the ground. "You guys aren't even being rational!"

Don glanced at the sudden display of frustration and nodded. "Leo would never lose his cool like that."

Leo stared at them in disbelief.

"However, we can't be totally sure." Don interjected. "I need to run some tests… and… we have yet to hear from the other suspect."

All eyes turned to the Shredder, who was staring at his stumpy right arm in disbelief.

No one noticed the dark shadow at the entrance to the lab. The shadow turned and fled the scene.

~.~.~.~.~

Leo sat restrained in a chair; his wrists were tied to the arm rests and his ankles to the legs of the chair. He glared daggers at the Shredder who was equally bound, with the exception of his stump limb, and sitting across from him.

His brothers stood around them, with arms crossed. Leo's glare was filled with animosity, and each of the brothers could sense it. Donatello cleared his throat.

Leo slowly turned to the turtle in purple, his glare replaced by an emotionless face.

"We're going to refer to both of you by your physical identity while we remain in the dark. These tests were mostly scientifically based and reflect on your thought processes. It came close, with Leo at five out of eight and Shredder at six out of eight tests correct." Don stated, reading off a sheet. He looked at Leo with a hateful glare that was echoed by his brothers.

Shredder looked up, his eyes glowed with glee and hidden malign intent.

Leonardo stared at the ground with an emotionless expression. "I never thought it would end this way…" He thought to himself. Leo took a deep breath and looked up at his brothers. "I suppose you plan on executing me now…" He said shakily.

"You don't even need to ask." Mikey spat, glaring angrily.

Leo inhaled and clenched his fists. "I respect your decision, but I cannot allow it. He is too dangerous."

He suddenly leapt out of the chair, dropping a piece of glass he had used to loosen his bonds. Leo quickly yanked a sai out of Raph's belt and charged at Shredder.

The tall human quickly leapt from his chair, he had cut at his bonds as well, and dodged the initial strike. Leo growled angrily and ran after the fleeing figure. "Shredder! Come back here you coward! You murderer!" He roared. Mikey, Raph, and Don quickly followed suit after recovering from the initial shock.

Leo hurled the sai at Shredder's ankle; the human leapt up and stumbled as he landed before continuing his run. Leo snatched one of his katanas from the ground and chased him through the entrance of the home, into the sewers.

~.~.~.~.~

Mikey had sprinted far ahead of his slower brothers; he panted but kept up his pace. His feet splashed in the water with each foot step. He began to hear more sets of splashes, and caught sight of Leo's blue mask tails fluttering. He snatched his nun chucks from his belt and began building their momentum and power in spins. His eyes narrowed and he sprinted faster, legs pumping, muscles contracting. Pushing.

He swung his right hand nun chuck down, hitting the back of Leo's leg with a crack.

The older turtle cried out in pain and stumbled forward onto his face into the water. He shook his head and instinctively rolled to his right. He quickly stood up, panting. Mikey glared at him with hell-born fury. "You're not getting away this time, you monster." Mikey snarled, once again swing the nun chucks on their respective chains. Leo's chest heaved with exertion and he wiped his brow with one arm. "Michelangelo, I don't want to fight you."

"You don't get to make that decision!"

Mikey charged, swinging his nun chucks with deadly accuracy. Leo ducked and side-stepped each blow, he leaped backwards to avoid a powered attack. His hand shot out and gripped Mikey's wrist. The younger turtle flicked his other hand, sending the nun chuck down to wrap its chain around Leo's wrist. Mikey then maneuvered Leo to the ground with the crushing of the chain. Leo growled as he was forced onto one knee with his right arm behind his back. "Mikey, let me go now." He warned. The younger turtle did not heed his warning. Leo twisted suddenly with surprising flexibility, sending the turtle in orange to the ground. Leo stood up and with a second glance, ran after Shredder. His legs pumped rapidly, despite his exhaustion. He focused only on moving his arms and legs. Leonardo's breathing grew more ragged with each step. He was so exhausted and focused that he did not notice Karai until she was upon him.

A katana came down in a fiercely powerful slash. Leo leapt back with a cry of surprise. Karai charged with her katana. Leo shoved her blade aside with a slash and kicked her defenseless shoulder, sending her into the wall. Water splashed wildly with their quick movements. Karai turned and hit the wall with her back. She glared at him. "You deceived me, Leonardo!" She snarled as she stabbed forward. Leo sidestepped and trapped her arms with his right arm. Leo bared his teeth and elbowed her with his right arm once, twice, three times before sending a hefty punch with his left hand into her face. Karai stumbled back into the wall and quickly brought up her katana as Leo's slashed down.

Leo's mouth was set in a grim line and his eyes were narrowed. His katana scraped against the flat side of hers with a squealing sound before hitting the hilt and snapping it off with a screech. Karai quickly moved her katana in a circle, throwing Leo's sword arm out and stopping him from slicing her hands open. Leo quickly rolled to his right and came to his feet, evading a downward slash. They circled each other slowly, trying to anticipate each other's moves.

"I thought you were honorable, Leonardo." Karai snapped. "It seems I was proven wrong, and you have dishonored my clan! You've turned us to wretchedness!"

"Get your facts first, and then you can distort them as you please." Leo replied before charging in again. Karai ran towards him and slashed at his waist. Leo leapt up and spun, slicing at her torso. She ducked and rolled under him to slash his back. Leo quickly turned his body and brought his katana up to block the strike with a clang and a flash of sparks. He pushed down and gripped her tunic, yanking her forward and down into the water. Karai hit with a heavy splash she grunted and growled in anger. Karai grabbed a chunk of mud and flung it back. It struck Leo's eyes and the turtle reeled back, wiping at his eyes. Karai growled angrily and surged forward while Leo was unsteady. Her footsteps splashed loudly in the sewer and the air whistled as Karai slashed her katana to decapitate Leo. The young terrapin turned, avoiding the slash and trapped her arm in the crook of his elbow. He kept turning until his elbow struck her jaw hard and solidly. A heavy pop sounded and Karai screamed. She fell back and Leo released grip of her arm.

He wiped the mud out of his eyes and turned at the sound of footsteps. Mikey's form came hurtling through the darkness towards him, the whish whish of his nun chucks resounded in the air. A sudden lance of pain shot through Leo's left shoulder. He switched the grip of his sword to that of a backhand. Leo quickly stabbed behind and turned while skidding back, yanking a katana blade out of his left shoulder with a muffled cry of pain. Karai was holding her bleeding side and glaring at him angrily. Suddenly she smirked. Leo froze at that and turned around to see the Shredder step out of the shadows and run his katana through Mikey's abdomen. Mikey impacted the sword hard. The blade penetrated his abdomen up to the hilt. Mikey dropped his nun chucks with a breathless cry of anguish. Leo's eyes went wide and his mouth opened in disbelief. "No!" He screamed.