When the turtles get word of the Kraang's return, they realize there is an even bigger threat coming to Earth.

Leo and Donnie disagree about their plan to stop the Kraang invasion; Donnie must step up as the leader of the bunch when Leo makes a mistake and is separated from the team.

When the Turtles are accidentally transported to the past, they happen to cross paths with a familiar ninja clan.

When the turtles get word of the Kraang's return, they realize there is an even bigger threat coming to Earth.

With the world at stake, the only thing of importance is that the Turtles complete their mission. No matter what ...

Leonardo considers asking Splinter for help while facing Shredder's new assassin; Donnie must put aside his rivalry with Casey in order to uncover a Kraang plot.

Leonardo considers asking Splinter for help while facing Shredder's new assassin; Donnie must put aside his rivalry with Casey in order to uncover a Kraang plot.

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The turtles engage in a difficult battle, as they make a desperate assault on TCRI to shut down the Kraang portal.

When Tiger Claw returns, he vows to hunt and destroy the turtles, as well as April and Casey. Meanwhile, Karai finds out the truth about her mother and real father, forcing her to make a life changing decision.

Leo stages a rescue for Karai against Splinter's wishes. While the mission is a success, Karai's knowledge of the truth makes her rush out to take her revenge on Shredder for killing her mother and lying to her for so long, leading to an unexpected turn of events.

Leo and Donnie disagree about their plan to stop the Kraang invasion; Donnie must step up as the leader of the bunch when Leo makes a mistake and is separated from the team.

After April receives a warning from her imprisoned father, she and the Turtles embark on a mission to save him and stop The Kraang from detonating a mutagen bomb in the city.

Leo takes the Turtles to train in the woods in an advanced ninja ritual; the Turtles must overcome their weaknesses and face their enemies to become a true ninja.

Leo tries to convince the team to rescue Karai; a master thief steals Shredder’s helmet.

When the Turtles go to the bizarre realm of Dimension X, Mikey is the only one who can figure the place out.

As the Turtles search for Karai, they are forced to deal with a city filled with Kraangdroids as well as Zeck and Steranko.

When Karai is brainwashed, she begins hunting the Turtles.

The Turtles must face off against a new enemy, The Rat King, who threatens not only to take control of the city, but of Splinter's mind as well.

After witnessing the Kraang in action, Karai realizes the seriousness of the alien threat and proposes an alliance with the Turtles....unless the Shredder finds out.

After being kidnapped by the hypnotized Karai, the Turtles are placed in deadly traps that they must work together in in order to escape. Splinter, in his efforts to save the turtles, is forced to face Karai in order to free her from Shredder's control.

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.

Snakeweed returns and begins abducting people. Tired of Raphael's constant criticism while trying to stop Snakeweed, Leonardo lets Raphael try his hand at leadership. While away from the group, Leonardo meets a female Foot Ninja named Karai, who tries to lure him to the dark side.

Donatello breaks into a secret Kraang detention center in order to rescue Kirby O'Neil, but ends up trapped inside with a deadly prisoner called the Newtralizer.

After encountering mutants and ninjas, Casey Jones decides to take on "pure evil" alone. When he meets Raphael, the two hot-headed fighters must put their dislike for each other aside and work together against a common foe.