In a world where darkness and despair are beginning to take shape, the Teenage Mutant Ninja Turtles, that legendary quartet of mutant warriors, are going through tough times. After the defeat of their arch-nemesis Shredder, Leonardo has retreated to solitary training in South America, convinced that he needs to learn to be an even better leader. Meanwhile, Donatello, Raphael, and Michelangelo have stayed in New York, leading a more normal life among the suburbs and alleys, but nostalgia and a lack of purpose are beginning to wear them down.
Everything changes when an ancient threat resurfaces: a mysterious phenomenon is opening portals throughout the city, letting loose creatures from other worlds and widespread chaos. Additionally, a businessman with dark interests is behind these events, seeking to unleash ancestral warriors he could use for his own purposes.
The Turtles, in an attempt to reunite and face the crisis, must overcome their differences and come together once more. Alongside their eternal friend April O'Neil and the brilliant master Splinter, the quartet embarks on an epic adventure that will lead them to rediscover not only their combat skills but also the bonds of brotherhood that made them invincible. Laughter, action, and poignant moments intertwine in this journey that will teach them that, despite the adversities, unity will always be their greatest strength.