In a wooded area outside Rio de Janeiro,a beautiful girl in a dress that doesn't cover much is being chased by a man who wants to kill her.Meanwhile, kickboxing champ David Sloan and his trainer Xian are on a plane to Rio as David is about to face Argentinian champ Martine.In Frank Lane's restaurant, it appears wealthy men are being set up with hookers. And where do the hookers come from? There is a large group of young girls in a room, who are shown what could happen to them. Remember the girl who was being chased?In Rio, Marcos and his sister Isabella work together to steal the camera David and Xian brought with them. David chases Marcos and discovers he is one of a large group of kids who are basically homeless, though their shelter is an unfinished hotel. David and Marcos become friends, and David and Xian try to keep Marcos and Isabella safe while working to improve their circumstances.Before the big fight, David participates in an exhibition to benefit the homeless. The people in charge of a fundraiser don't seem to get the irony of treating the very people they are helping as second-class citizens.In an exhibition, no one is supposed to get hurt. Martine doesn't seem to understand that and David gets involved when he sees how Martine's opponent is treated. They will get a rematch.Frank is Martine's manager and he becomes friends with David. But the audience knows he wants something. Marcos wants to set David up, and he too has a good time dancing. David gets to demonstrate his skills.Eventually, David and Xian must fight, using weapons rather than just their bodies. David also gets a new trainer who is quite brutal compared to Xian. And the outcome of the fight with Martine could have deadly consequences for one of the stars.