After Donnie upgrades Metalhead's artificial intelligence, the other Turtles become suspicious of the new, sentient Metalhead. At the same time, the Turtles stumble upon the Kraang's plot where they have been capturing the mutants (ranging from Snakeweed, Spider Bytez, Dr. Tyler Rockwell's mutant form, Pete, Justin, a Parasitic Wasp, Newtralizer, Kirby O'Neil's mutant form, Slash, and a Squirrelanoid) so that they can control them.