The story begins with the turtles having separated after Shredder's defeat. Leonardo is on a mission in South America, while the others are trying to find their place in the city. When an ancient power awakens and unleashes monsters into the world, the turtles must overcome their differences and work together again. With the help of April and Casey Jones, they face the industrial magnate Max Winters, who is trying to use the monsters to attain immortality.