When Donatello's latest invention gives failed inventor and perpetual loser Baxter Stockman enhanced abilities, the turtles must learn to use their heads instead of brute force to defeat him.

When Donatello loses confidence in his bo staff as an effective weapon, he constructs Metalhead, a fully armed robotic turtle based on Kraang technology.

When simultaneous threats from the Purple Dragons and Baxter Stockman’s mechanical Mousers force the Turtles to split into two groups, Donnie & Mikey must prove that their “B Team” is just as valuable as Leo & Raph’s “A Team.

Michelangelo befriends Leatherhead, an unstable mutant alligator who possesses a strange piece of Kraang technology, but the other Turtles aren’t sure whether Leatherhead is a friend or a foe.