A drifting ex-soldier turns underground fighter with the help of a just-released ex-con, pitting him against corrupt cops and hired killers now gunning for him and all those he cares about.
After facing brutal humiliation in the ring, a young karateka travels to China in order to study the ancient art of Shaolin Kung Fu, becoming the first American Shaolin.
Raised as a slave, Danny is used to fighting for his survival. In fact, his "master," Bart, thinks of him as a pet and goes as far as leashing him with a collar so they can make money in fight clubs, where Danny is the main contender. When Bart's crew is in a car accident, Danny escapes and meets a blind, kindhearted piano tuner who takes him in and uses music to free the fighter's long-buried heart.
Russian inmate Boyka, now severely hobbled by the knee injury suffered at the end of Undisputed 2. No longer the feared prison fighter he was, he has declined so far that he is now good only for cleaning toilets. But when a new prison fight tournament begins - an international affair, matching the best fighters from prisons around the globe, enticing them with the promise of freedom for the winner - Boyka must reclaim his dignity and fight for his position in the tournament.