Shredder and the Kraang team up! Now as a combined force, the Turtles face double the threat! And with new mutants lurking throughout New York, and the return of evil villains including Karai, the Rat King, and Foot Bots determined to take down the lean, mean, green team, get ready to join Leo, Raph, Mikey, Donnie, April, and new ally, Casey Jones, as they fight back and take the ninjutsu battle action to new rooftop heights!