In the wake of a botched bust meant to shut down an organ-trafficking ring, undercover cop Kit (Wu Jing) has his cover blown. As payback, the sinister gang sends him to a Thai prison run by a corrupt warden (Zhang Jin), who swaps Kit’s identity with that of a prisoner facing a life sentence.

Meanwhile, Chai (Tony Jaa), a guard at the prison, is desperate to find a bone-marrow donor who will save his daughter’s life. Though aware of Kit’s wrongful imprisonment, Chai has no choice but to thwart the innocent man’s escape attempts as he tries to save enough money for the life-saving operation. These two trapped men will end up fighting to save themselves as well as the lives of their loved ones, and no prison can hold them.