The team tries to deal with the possibility that Leo will not get better; a new mutant captures Raphael.

When he gets upset, Mikey flees and befriends a mutant frog in the woods, only to learn the frog and his family have nefarious plans.

When the Turtles return to the city to search for Splinter, they discover that the city has been overrun with Kraang.

Donnie finishes a new batch of retro-mutagen in hopes of saving Karai; the Turtles are hunted by Shredder's new henchmen, Bebop and Rocksteady.

The Shredder kidnaps and experiments on the Mighty Mutanimals.