Ryan Cole (Scott Adkins), a retired underground fighter, has put his violent past behind him and now lives a quiet life running a gym for troubled youth. But when his younger brother, Jake, a small-time gambler, gets into trouble with a powerful crime syndicate known as The Blood Circle, Ryan’s world is shattered. Syndicate leader Viktor Dragunov forces Ryan to enter a brutal underground tournament in exchange for Jake’s life.

Ryan enters The Blood Circle, a no-holds-barred fighting tournament featuring the world’s deadliest fighters. Each round brings more violence, and Ryan faces off against mercenaries, assassins, and martial arts masters. Meanwhile, he learns that the tournament is more than just a fight: it’s a front for a sinister organ trafficking operation, where losing means death.

Ryan forms an uneasy alliance with Mei Ling, a rogue assassin seeking revenge against Dragunov. Together, they conspire to bring down the union from within.