When a powerful foe returns, the Turtles' only hope lies within the most dangerous place they've ever been: Splinter's mind. / The Turtles meet Splinter's distant relative and discover a powerful new ally.
The Dark Armor needs one last piece to it's completion, and Draxum wants to trade it in exchange for the lives of the turtle brothers. But Splinter wants to save them with the help of old allies before this happens.
After forgetting about a very important mission, the turtle brothers want to make it up to Splinter by becoming the best ninjas they've ever been on their mission to stop the dark armor from being re-assembled.