Beyond the human realm, there is a magical race of beings who control the tides and the changing of the seasons. One of these beings, a young girl named Chun, seeks something more—she wants to experience the human world! At sixteen, she finally gets her chance and transforms into a dolphin in order to explore the world that has her fascinated. But she soon discovers that it's a dangerous place and nearly gets killed in a vortex. Luckily, her life is spared when a young boy sacrifices himself to save her. Moved by his kindness and courage, she uses magic to bring him back to life only to learn that this power comes at a serious price. On a new adventure, she’ll have to make her own sacrifices in order to protect his soul until it is ready to return to the human world.

After supervillain Shredder escapes custody, he joins forces with mad scientist Baxter Stockman and two dimwitted henchmen, Bebop and Rocksteady, to unleash a diabolical plan to take over the world. As the Turtles prepare to take on Shredder and his new crew, they find themselves facing an even greater evil with similar intentions: the notorious Krang.