"Karai has not returned for some time." said Shredder to Dogpound and Fishface, "I want you two to search the city for her and bring her back."
"Yes, Master Shredder." they said in unison.
The turtles and Karai were on their way to T.C.R.I. when they saw Fishface and Dogpound.
"Karai," said Dogpound, "Your father's worried about you."
"If you're referring to Shredder tell him I know he's not my father."
"What?" said Fishface.
"Donnie ran a DNA test on her." said Leonardo, "She's actually Splinter's daughter, kidnapped by the Shredder during the fire 16 years ago."
"Since I know that, now," said Karai, "I have no problem doing this!" she kicked Fishface off the roof, his now broken legs taking the brunt of the fall.
"Great." said Raphael, "Now what about Dogpound?"
"Hadn't thought about that."
"Luckily I'm prepared for this." said Mikey as he pulled a small object from a pouch on his belt.
"An egg?" said Karai.
"No." Mikey said. And he threw the object down, surrounding them in a cloud of purple smoke. When the smoke cleared, Karai and the turtles were gone.
Back on the ground in an alleyway, Karai said "What was that?"
"One of my Ninja Smoke-bombs." said Donatello, "I drilled a hole in the top and bottom of an egg, emptied it out, let the insides dry-"
"Never mind the science stuff."
"Okay." The resumed on their way to T.C.R.I.
"What do you need me for?" asked April, still chained.
"You know how you lost your mother sometime after you were born?" said Kraang Prime.
"How did you know?"
"I have my ways of knowing, like the T.C.R.I. casualty records."
"Your mother worked for T.C.R.I., until an accident occurred days before your birth. She accidentally discovered our Mutagen lab. She tried to leave carefully, but she bumped into a Kraang outside of its exosuit. It entered its exosuit and shot at her, for fear of having their plan exposed. It missed her, but hit a tank of experimental ooze. It poured all over her. She seemed fine, and you were fine, too, when you were born. But the next day she died. Because of this near-mutation, your DNA contains some Kraang. And we need a mixture of human and Kraang DNA in order to complete the Mutagen."
"Why?" Before Kraang Prime could answer, the turtles and Karai arrived.
"What is she doing with you guys?" April asked.
"She's on our side now." said Leo.
"What convinced her?"
"Her true father."
"We'll discuss it later." said Karai, "In the meantime let's take down some Kraang."
"I'm sorry, turtles," said Kraang Prime, "I'm afraid we have you outnumbered."
"What do you need April for, anyway?" asked Donnie.
"I was just about to tell her that. Her mutant DNA is needed to perfect the Mutagen to regenerate our lost bodies."
"What?" said Raph.
"During the war between the Kraang and Utroms back in Dimension X, the Utroms created a device which caused our bodies to deteriorate. Before they fully deteriorated we developed a substance to make us able to survive with only our brains, however we still strived to recreate our true bodies. Now that there is a human with a hint of Kraang in her, we can finally succeed in our quest and defeat the Utroms!" Kraang Prime pushed a button that pulled April over a tank of goop, not the complete Mutagen, but merely an ingredient. They lowered her into the tank and extended a needle and pricked April's arm. The blood that came out mixed with the ooze. April was pulled out of the vat and some other chemicals were poured into it.
"The Mutagen has reached the point that is the point of completion, Kraang Prime." said a Kraang supervisor.
"Excellent." said Kraang Prime, "Now to test it. You there, Kraang with droid number 17976, you will be our guinea Kraang."
"Yes Kraang Prime." said the selected Kraang. It exited it's exosuit. Kraang Prime collected the new Mutagen in one of the containers and poured a little on the guinea Kraang. It grew a new body. It appeared like a lizard mutant, not unlike a somewhat altered form of Leatherhead.
"Kraang's body has been subject to the process that is the process of regeneration." said a Kraang.
"This is bad, right?" said Michelangelo.
"Unless you want the human race to be eaten by the Kraang." said Donnie.
"Okay." Mikey drew his nunchaku and swung at the newly regenerated Kraang. However they just bounced off of the scaly hide. He converted it into a Kusarigama and swiped at the monster and left a mark, but it immediately healed.
"Man," said Mikey, "this is one tough nut to crack. Also it looks a lot like Leatherhead."
"And this is only the beginning," said Kraang Prime, "soon there will be millions of these as there were before. They will reproduce and devour every life form on this Earth, we need plenty of strength to finally destroy the Utroms! Also, it is no coincidence that it looks like the creature you call Leatherhead, for he was mutated as an experiment to make new bodies for the Kraang out of Earth reptiles."
"Okay." said Mikey. The reptilian monster swiped at the turtles. The survived, however, by tucking into their shells.
"I love being a turtle!" said Mikey.
"How do we stop this thing?" said Raph.
"There's only one person I know who can defeat this thing." said Leo.
"Who's that?" said Raph.
"Leatherhead." Mikey got a pleased look on his face, Donnie got a frightened look.
"Donnie," said Raph, "no need for the long face, it'll just get longer when Leatherhead grabs it again." Donnie turned to Raphael, his eyes all white and the scene's background is of a thunderstorm (something like when Mikey brought up Leatherhead's habit in the episode "T.C.R.I.")
"How are we going to get him out of Dimension X?" said Mikey.
"We open the portal, go in, and tell him we need his help." said Leo.
"Right." said Mikey. He wrapped his kusarigama chain around the lever and pulled it. They stepped through into Dimension X.