Jimmy "The Lightning Bolt" Lee is a former mixed martial arts champion who returns home and is asked by his father figure, Charlie, to teach a group of inner city kids martial arts in preparation for a tournament. The reigning junior national champions, the Beverly Hills Scorpions, are coached by the very cocky and arrogant Ted Barret, who is a former rival of Jimmy's. With help from local food truck vendor Big Mama, Jimmy's team becomes the Underdogs. As the Underdogs prepare for the big tournament, both the kids and Jimmy learn some lessons from each other that will make their bond stronger as they prepare for a showdown with the Scorpions.