-Frank Leone(Sylvester Stallone) is a skilled mechanic and pro footballer, and also a model prisoner at the end of his sentence in a low security prison. One night, while sleeping in his cell, guards arrive and forcibly take him to Gateway Prison, a maximum security prison. The warden there, Warden Drumgoole(Donald Sutherland) claims that Leone will serve hard time because he escaped from Treadmore on Drumgoole's watch. He escaped because his mentor and friend was dying; and he went to the press about the warden's treatment of prisoners, resulting in his transfer to Gateway.
-While in Gateway, Leone befriends fellow inmates Dallas(Tom Sizemore), Eclipse(Frank McRae), First-Base(Larry Romano). The 4 restore a Ford Mustang, which Eclipse nicknames Maybelline. After Leone reluctantly allows First Base to start it, he refuses to turn it off, and drives the Mustang out of the garage and as punishment, Drumgoole has Chink Weber(Sonny Landham) and other inmates destroy the car. As punishment, Leone is subjected to solitary confinement in a small, roach-infested chamber for 6 weeks. After weeks in the hole, Leone is getting beaten by prison guards when Capt. Meissner(John Amos) stops them. He learns that the warden authorized the beating
-Leone gets intimidated by prisoner Chink, who shows off his belt buckle(A Ford Mustang symbol). Chink steals Leone's food in the mess hall and taunts him. Drumgoole apparently has ordered the letters addressed to Leone from his girlfriend Melissa(Darlanne Fluegel), be stashed away, but Braden(William Allen Young), the prison's sole conscientious guard, gives them to Leone. The warden wants an excuse to slap Leone with more time, so he allows Chink and his bully friends to kill First-Base in the gym. Leone fights and defeats Chink, but does not kill him. But he gets stabbed in the back with a shank.
-Leone recovers in the prison infirmary where Wiley(John Lilla) claims to be an old friend from Treadmore. He says that Drumgoole actually has agreed to reduce Wiley's jail time if he will rape and murder Melissa. Leone goes nuts. Dallas offers help to Leone to escape and plays along but eventually delivers Leone into Drumgoole's hands. He says that he does not make deals with prisoners; Dallas will rejoin prison population, who now is known as a stool pigeon. Dallas attacks Drumgoole, whose guards pummel and almost kill the snitch. The warden leaves his men to subdue Leone, who is raging when he finds out that Drumgoole wanted him to escape so he would receive a mandatory 10 year sentence.
-Wiley shows up as one of Drumgoole's guards. The guards attempt to shove Leone's face into a cloud of hot steam but he pulls one of the guards into the steam instead. He knocks out Wiley and fights Manly(Jordan Lund), but defeats him and goes to help Dallas who is dying. Leone is then attacked from behind by Manly and Dallas, who is already dying, electrocutes himself and Manly with a high voltage cable
-Enraged, Leone breaks into Drumgoole's offic and takes him into the room with the electric chair. Leone activates the generator and secures his hand to the switch. Capt. Meissner, Braden and their men point their guns at Leone, but if he is shot he will trip the switch and kill Drumgoole. The warden confesses to his plan o increase Leone's time. Frank pulls the switch, but nothing happens as Leone removed the main fuse. Meissner's men take Drumgoole to the hole. And Meissner and Braden take Drumgoole into custody.
-Meissner makes a judicial inquiry into the matter and Leone only serves the jail time he received in the 1st place. Frank leaves prison to the cheers of the inmates. He meets up with Eclipse one last time and gets a Cuban cigar which was supposedly given to Eclipse by Fidel Castro. Leone parts ways with Meissner, saying that he will miss the tough captain's incredible smile.