The film opens with a turtley prologue that reveals their evolution and ultimate triumph over their nemesis, The Shredder. Fast forward 3000 years, we meet Yaotl, a warrior-king, leading his four generals in a conquest for global supremacy. Following the defeat of a Central American empire, Yaotl discovers that a rare celestial event, known as the Stars of Kikan, occurs every 3000 years, unlocking a powerful portal marked by a blinding light. This portal grants Yaotl immortality but turns his generals into stone, unleashing thirteen monstrous creatures that lay waste to his army and remain free to this day.
In the present, we are transported to Central America, where corrupt army officials pilfer supplies from a local village. Their search for riches ends abruptly when an unseen enemy ambushes them, leading their truck and the stolen goods back to the village by dawn. Meanwhile, April O'Neil ventures through the forest, where she encounters Leonardo. Leo is curious about his brothers' whereabouts since he left. Donatello has taken on the role of a one-turtle tech-support service, while Michelangelo runs a party planning business called Cowabunga Carl. Raphael, however, embraces the night as a vigilante known as The Nightwatcher, taking down bank robbers.
April, now running a shipping company, has come to the region to unearth an ancient artifact. Leonardo, having spent a year in Central America seeking personal growth as a leader, is hesitant to go back, fearing Splinter's disappointment. Despite April’s pleas, he remains firm, disappearing before she can press further.
Back in New York, Mikey drives his Cowabunga Carl van through the bustling streets and navigates to their lair via the sewers. Engrossed in the exploits of Nightwatcher, he reminisces about his vigilante days, drawing playful mockery from Donatello and Raphael, who are at odds over Mikey's quick adjustment to a less heroic lifestyle. Master Splinter intervenes to quell the brewing conflict as Raphael retreats to his room.
At the docks, April supervises the delivery of an ancient statue, which is the last remnant of the Four Generals that Max Winters, the head of WintersCorp, intends to collect. A mishap leads to an alarm that seals the building, just as Karai and the Foot Clan make their entrance, eager to regain power after the defeat of their former leader, Shredder. Winters has ambitious plans that involve dangerous alliances with the Foot Clan, who are quick to respond to his call for help.
As Nightwatcher, Raphael crosses paths with Casey, who unravels his secret identity. Together, they attempt to apprehend criminal elements in the city, while Splinter reveals to Leonardo the emotional toll his absence has inflicted on Raphael. Despite initial friction, the brothers unite over shared goals, but tensions escalate as they face off against formidable foes, including the Stone Generals.
Unexpectedly, during an encounter, Raphael and Leonardo collide in a fight where Raph emerges victorious, only to be haunted by the potential tragedies of their rivalry. Meanwhile, the Stone Generals have their own agenda, conspiring against Winters as they realize the stakes surrounding their immortality.
In a frantic series of events, the Turtles and their allies—guided by April and Casey—embark on a mission to thwart Winters' plans during the climactic celestial alignment. Amid chaos, they brace for a showdown inside WintersCorp, fighting not only the Generals but the monsters that emerge from the portal. Each Turtle engages in fierce combat, proving their skills against the Stone Generals, while April and Casey race against time to secure the thirteenth monster and shut down the portal.
With teamwork at the forefront, the Turtles face their adversaries valiantly. After an intense battle where April's bravery shines, they manage to disrupt Winters' plans, resulting in the monsters and Generals being banished through the portal. As they retreat, Raph offers his newfound respect to Leonardo, showcasing the growth they've both experienced.
In the aftermath, back at their headquarters, Splinter reflects on their journey by placing the helmets of their foes on display, signifying a memorable chapter in their lives. Under the glow of the city lights, the Turtles leap across rooftops, as Raph contemplates the deeper meanings of heroism and the bond of family they share, culminating in a heartfelt journey of growth, redemption, and loyalty.
