After witnessing the Kraang in action, Karai realizes the seriousness of the alien threat and proposes an alliance with the Turtles....unless the Shredder finds out.

When Shredder plans to create an army of mutants, the Turtles must rely on the help of the Pulverizer, who was recruited into the Foot (to be expendable) and volunteers to gather information on the inside on their behalf. When he agrees to be a test subject for a stolen supply of Kraang Mutagen, the Turtles rescue him, but not before he recklessly gets himself mutated.