In  Teenage Mutant Ninja Turtles: Mutant Mayhem , after years of being sheltered from the human world, the  Turtle brothers  set out to win the hearts of New Yorkers and be accepted as normal teenagers through heroic acts. Their new friend  April O'Neil  helps them take on a mysterious crime syndicate, but they soon get in over their heads when an army of  mutants  is unleashed upon them.