Kurt Sloane is the younger brother of Eric Sloane, the United States kickboxing world champion. After another successful title defense, Eric is enticed by the media to compete in Thailand, where kickboxing was started, to further establish his legacy. Eric and Kurt travel to Bangkok to fight Tong Po, Thailand's undefeated top fighter. Eric is supremely confident but Kurt is apprehensive, particularly after witnessing Tong Po kicking a concrete pillar to prepare for the fight. Kurt begs his brother not to fight, but Eric dismisses any concerns.
One year after the events of the first film, it is revealed that kickboxing brothers Kurt and Eric Sloane have been killed by Tong Po in Thailand. David Sloane (Mitchell), the last surviving brother, struggles to keep the family's Los Angeles kickboxing gym afloat. He offers free kickboxing lessons to local kids, often demonstrating a technique he calls the "rock and the river" which allows him to defend against attacks while blindfolded.
The movie opens with a distressed woman being chased through a tropical forest by an unknown pursuer. It is soon revealed that the woman is attempting to escape from Frank Lane, an American running an illegal child sex ring operation in Brazil. Upon being recaptured, she is taken back to Lane's home and executed in front of the other slaves, as punishment for her actions.
The film opens with a recap of earlier events in the series as David Sloane writes a letter to his wife, Vicky. After being framed for murder by Tong Po, Sloane has spent the last two years in prison, while his wife has become the sexual captive of his old nemesis, who has since become one of the most powerful drug lords in Mexico.
After David Sloan is murdered, it's up to kick-boxing champ Matt Reeves to avenge him...