Heavyweight Champ George "Iceman" Chambers is sent to a Russian jail on trumped-up drug charges. In order to win his freedom he must fight against the jailhouse fighting champ Uri Boyka in a battle to the death. This time he is not fighting for a title, he is fighting for his life!

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.