In 2001, when all prisons have been
privatized, super-strong and durable Ricky Ho is sent to one for manslaughter after killing a crime boss responsible for his girlfriend's death. The prison is divided by
cardinal directions, with each wing having a member of the "Four Heavenly Kings" ruling over it. Ricky is placed in the North wing, where he witnesses an inmate named Wildcat disfigure an elderly inmate. Ricky partially blinds Wildcat, who then pays obese inmate Mad Dragon to kill Ricky, while the disfigured inmate commits suicide after Wildcat stops his
probation from clearing. Mad Dragon attacks Ricky in the shower, but Ricky kills both Mad Dragon and Wildcat. Fearing that Ricky may inspire the other prisoners to revolt, the one-eyed Assistant Warden orders the North wing leader Ah-hai to publicly execute him. Hai
disembowels himself in shame after Ricky beats him and during the act tries to strangle Ricky with his intestines, forcing Ricky to kill him. The rest of the Gang murder Hai's godson Sa when he refuses to take revenge on Ricky, so Ricky burns their
opium farm. The Gang restrains Ricky, but before they can kill him, the Assistant Warden learns that the head Warden is returning from vacation and forces everyone back to their cells. The Assistant Warden floods Ricky's cell with
cement, freezing him in place. The Warden and his spoiled son return and the former interrogates Ricky, but is interrupted when Tai Zan, the East wing leader, bursts through a wall to fight Ricky. Ricky brutalizes Tai Zan, and the Warden tries to crush them both to death under the cell's
hydraulic ceiling, though Ricky holds it off in an effort save Tai Zan's life. The Warden shocks him with a
taser to make him stop, only for Tai Zan to hold up the ceiling long enough for Ricky to escape before Tai Zan dies. The Warden orders Ricky buried alive for a full week and promises him freedom if he can survive, which he manages to, though the warden still denies him freedom and leaves him chained up in his cell. An inmate named Freddy sneaks Ricky his food, but a snitch informs the Assistant Warden, who kills Freddy and taunts Ricky with his body. Enraged, Ricky breaks free, kills the snitch, and blinds the Assistant Warden's other eye. The inmates riot and mutilate the Assistant Warden, whom the Warden kills, annoyed with his incompetence. Ricky twists the West wing leader Huang Chung's limbs to neutralize him, while the South wing leader is killed by the Warden when he flees in fear. Having gone too long without his medication, the Warden transforms into a hulking creature whom Ricky barely defeats by shoving him feet-first into a
meat grinder. With the Warden dead, Ricky walks outside to find the guards and inmates still fighting each other. He stops the fight by presenting them with the Warden's severed head, then punches the wall of the prison, collapsing part of it with a single blow. Declaring "you're all free now", he walks through the opening in the wall to freedom. ==Cast==