"Leo!" Raph called, starting forward. He halted when Leo swung his face to glare at him. Or, that's what it looked like. Leo still had his blacked-out mask on, so Raph couldn't really tell.

Again, Leonardo snarled, and Raph backed up, holding his hands out carefully. Don stood slowly, and Leo's gaze drilled into him.

"Leo… what's happened?" he asked through the glass, standing next to Mikey. Leo hissed then, a very clear sound. Startled, Don backed away from Mike, and Leo calmed down right away.

"My shell…" Don whispered, covering his mouth with his hand. Tears sprang to his eyes. "YOU MONSTER!" he shouted, presumably at Bishop. "You #&ing monster!"

"What's going on?" Mikey asked, putting his hand on Don's arm. However, a growl from Leo stopped him. It was motherly, which startled Mike. He retreated, and then went over the sound. It was like Leo was commanding him to stay away, but… he said it using a warm growl, like a mother would to her hatchling.

"He's… he's…" Don broke down, sobbing into his hands. Raph wrapped him in his strong arms, and Don shifted to look at Leo through the glass. "Bishop took away his rational thoughts," he said sadly.

"What?!" Mike turned to Leo, who was watching him lovingly. Mikey swallowed. "So… I'm truly his Kalian, to him?"

"Yes. And judging by the way he looked at us," Raph paused. "Bishop told him we hurt you." Mike looked up sharply. "Listen. He talked to me before April and Casey picked us up. Mikey, his new instincts tell him that you're a defenseless – well, not quite – dragonet. To him, that means that he, a dragon, has to protect you. Don and I… are outsiders to him, "dragons" who could hurt his "dragonet" by being too rambunctious. If Don's right, then Leo probably won't trust us again, and he could very well kill us. That might be why he's over there and we're in here."

Mike put his hand on the glass wall, staring at his brother… his Kavara.

"Touching," Bishop's voice said laughingly over the speakers. "So, which one of you is Koriat? Black Fire?"

Raph looked up but remained silent.

"I think I can guess anyway. You are correct, Donatello. The thing that turned Leonardo into Kavara is called RTS. Rational Thought Serum. Therefore, I call what has happened TAS. Transformation into Animal Syndrome," Bishop laughed. "It's a pity, really. He can still talk and understand English. But, I suppose that's okay. We've only given him the first dose."

"W-what are you doing?" Don asked shakily.

"We're studying dragon-turtle interactions," Stockman's voice said. "It just so happens that we have the perfect candidate. Kavara is quite… dangerous, it seems." As if in answer, Leo straightened and tried to release his hands. His shell glowed red and so did his plastron, and he stopped, looking down, and growled.

"Well, with that touching reunion, I think we're done," Bishop said. Leo's cell door opened and he turned to it, his wings unable to open because of the metal that encased the joints. Don watched as Leo seemed to swell when Stockman approached. They couldn't hear anything, but Leo's mouth moved and Stockman's hologram laughed, then shot his arms forward to grab Leonardo.

However, Leo surprised them all, running forward and under the arms. Unable to use his hands or feet, the winged turtle jabbed Stockman's robotic body with his horns. They punctured and electricity shot through both "people".

Leo was flung into the far wall as Stockman flew out the door. Shaking his head, Leonardo stumbled to his feet dazedly and ran out of his cell. His brothers tried to see him, but they were unable to as he disappeared.

"What's he up to?" Raph wondered aloud, looking at the wall. Blood was smeared on it, the dark red blood that signaled Leo was hurt. "Aw, shell."

Gunshots fired outside for a moment, and a dim roar could be heard. Then, silence. Terrible, horrifying silence. Mikey whimpered and clutched Donnie, looking towards the door. Raph shifted so his little brothers couldn't see the blood in the other cell.

Suddenly, the door clanged. It slowly opened, and Raph stepped in front of his brothers to protect them. However, he was unprepared for Leo's entrance. The turtle was breathing heavily and limping, but alive. Several dings in his plastron and shell made Donnie glad Bishop had made his bony plates metal.

He fanned his wings gently, and blinked. Donnie ran forward and hugged Leonardo. Mikey did as well, and Raph was watching fondly, wishing he had a camera.

"Leo… what happened?" Don asked finally, inspecting their brother.

"Their RTS thing worked… for a while. It seems our reptilian blood naturally filters it out into the stomach, where it is destroyed. Who'd a thunk?" Leo asked, hugging Mike and Don. "But it's over now. Let's get out of here."

Raph looked at Leo's natural shell, lying on the floor. Leonardo followed his gaze and bent to pick it up tenderly. "Hm. Well, I guess I'd better get used to the loss. This one is much better!"

Mikey smiled and rapped the metal now covering their brother's chest and back. "Boy, I'd hate to have you body slam me!"

Don was checking Leo's wings over, and found that, other than a couple bullet holes and a few bruises, they were fine. Except the right wing joint; it was shattered completely. He wondered why Leo didn't act like he was in pain, but when he looked closer, he saw that the metal of Leo's shell was moving, pushing the bone back in place and sealing it together somehow.

"Hey, your new shell's made of nano-bots!" Donnie exclaimed. "That's incredible."

"Glad you appreciate my work," Bishop's voice hissed coldly. "Too bad you won't live to get one of your own." Bishop pressed a button and Leo stiffened, then collapsed, unconscious. "It has its perks."

Donnie and Raph stood over Leo, who was being shaken by a terrified Mikey. "Don! He's not breathing!" Don's blood ran cold. Raphael growled at Bishop and launched himself at the human while Don whirled and checked Leo's pulse. Sure enough, it was gone.

"No!" He and Mike turned Leo over and Don started CPR. What killed him? Don wondered even as he bent to breathe into Leo.

"You can try to resuscitate him, but it won't work," Bishop said smugly, tossing Raph into a wall. The red-banded turtle leapt back into the fight with vigor. "He's got – oof!"

"Shut up!" Raph yelled, slamming his fist into Bishop's stomach. A small remote fell out of his hand and slid towards Mikey, who picked it up and was about to smash it when he saw an icon on it. He quickly looked at Leo's metal plastron, which held the same symbol. A green button was on the top, a red on the bottom. The red light in the middle was lit.

"Donnie! Back up a moment!" Please let me be right, Mikey fervently wished, pushing the green button and watching Leo.

His Kavara's metal plastron and shell twisted and Leo took in a breath… then another. He coughed and sat up, only to be swamped by Mikey and Donnie.

"Raph! Raph!" Mikey called, distracting their hothead brother. "Leo's okay!"

"Great! Help me kick this bozo's butt to next week then!" Raph ordered, leaping out of range of Bishop's well-aimed foot.

Leo leapt to his feet and joined Raph. Between them, they managed to knock the crazy scientist out and locked him in the cell. Gripping Leo's old shell and the remote that controlled their brother's life and death, Mikey looked around, horrified. Stockman's robotic body was completely torn apart, and three guards were dead… pretty much gutted. Leonardo's arms wrapped around him, his wings closing over them both.

"I thought I lost you," Mike whispered, leaning into Leo and dropping the shell and remote.

"You will never lose me," Leo promised, hugging his Kalian fiercely. "As I will never lose you." Leo let go and backed up, letting his wings close. Raph was staring at the gory scene around them, and Donnie was examining the hallways.

"Where do you think Master Splinter is?" he asked. Leo cursed himself; he'd totally forgotten about Master Splinter!

"I'll see if I can smell him." Leo looked around. "But with all this blood, I surely won't be able to." He kicked a corpse and walked away. Raph was staring at him, Mikey's jaw dropped, and Donnie was too engulfed with looking at the shell and remote to notice.

"This way," Leo's voice called out from the right hand tunnel. "I smell them."

After a few turns and countless hallways, the four brothers found a cell with a window. Through that window, they say Master Splinter, meditating. Leonardo opened the door forcefully – he didn't have the combo, Mikey joked – and helped their Sensei out of the cramped chamber. Then, he opened the door to April and Casey's, and they climbed stiffly to their feet and walked out, gawking at Leo.

Mikey had the remote in his hand and was looking at it thoughtfully. Leo glanced at him fearfully.

"What're you doing?" the winged turtle finally asked.

"Just thinking… This thing puts you to sleep, kinda. I wonder… Would it work to shut you up during a lecture?" Mike asked, tossing the remote from one hand to the other.

"Careful!" Donnie shouted, grabbing it from the youngster. "I don't know if we can reverse the effects of this thing yet."

"I'm just saying…"

"He's right," Raph chuckled. "We can just shut Leo off when he starts acting too bossy."

"Yes," Donnie allowed, "but if Bishop has more than one, he can also kill Leo with it."

"He's only got one," Leo said. "And you're holding it."

"How do you know?" Donnie asked, looking up and catching his brother's eye. April cleared her throat.

"Let's get outta here before guards show up!"

"Aw, don't worry. We've got Leo here to protect us," Mike told her.

"She's right. We should go." Silently, the turtles and rat and humans headed for clean air, following Master Splinter. It was dark when they got outside.

Leo breathe in happily. It was good to be alive.

A/N: Well, only one more chapter to go! Hope you've all liked it… Please, review. Until I get thirty reviews, I won't be posting the next chapter… and don't you want to know how this ends? ;-)