Casey Jones steps up and takes on pure evil. Meanwhile, the Turtles learn a shocking secret about April's past, and come face-to-face with another mutant turtle called Slash, a fungus mutant spreading through the sewers, a rewired Metalhead, and the Rat King!

Animated. Based on characters created by Peter Laird and Kevin Eastman. Originally broadcast as episodes of the television program in 2013-2014. Special features: 6 shorts: "The mutation of a scene" ; Meet Casey Jones.

Slash and destroy --The Kraang conspiracy -- The good, the bad, and Casey Jones -- Fungus humungous -- Metalhead rewired -- Of rats and men.