Four turtle boys who are as close as brothers have been living in a secret sewer. Under the training of their master (voiced by Jackie Chan), they become "Ninja Turtles" with superb kung fu skills. The four little turtles, eager to be accepted by humans, start tracking a mysterious criminal group with the help of their human friend April. However, with the arrival of a powerful army of mutant creatures, the Ninja Turtles, who are also mutant creatures, know that big trouble is coming...