Donatello experiments with mutagen in an attempt to find a cure for April's mutated father. But one of his expirements goes wrong and he is unleashed in the city.

Mikey struggles to convince the others that a new mutant is trying to attack and capture people using living pizzas.

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.

Michelangelo and Casey become friends with Mondo Gecko, a radical, skateboarding, reptilian teenager.

The Turtles must gain the trust of the Utrom Council in order to find the next piece of the black hole generator.

Raphael must overcome his fear of insects to lead the team when they are forced to battle Stockman-Fly's new insect minions.

When the Turtles and Renet return to a present-day New York City infested by an undead army of monsters, they realize they may have made the situation even worse.