After eluding numerous convictions for ten years, New York City notorious criminal Lou Gannon is finally convicted for armed robbery and murder. He is sentenced to 20 years in a maximum-security prison. Once there, Gannon is already planning his escape. He meets several inmates that he already knew on the outside. One of them is old acquaintance Doc, fourteen years into a long sentence. Doc knows the prison better than the guards themselves. Another key man is Ed 'Bugsy' Kyle. He's a violent psychopath who is the most feared inmate and who controls the rest of the inmates. Doc, Bugsy and their tight group agree to allow Gannon be in charge when he reveals that he has an escape plan involving organized help from outside the prison. Gannon's cellmate, young criminal Rudy Hernandez is a former gang member who wanted to go straight, had a job and wanted to get married to his girlfriend. Unfortunately, Rudy messed up and agreed to be the getaway driver for a gang during a hold-up. For this deed he got 5 years in prison. Rudy confesses to Gannon that he wants to be a model inmate in order to make parole for good behavior. During the following months, Gannon gets a desk job in guard captain Starkey's office while Rudy works as mechanic in the prison motor-pool. Gannon arranges the smuggling of various weapons into the prison, including a Thompson sub-machine gun that arrives in small parts concealed in blocks of soap and bales of cotton. When the inmate taking care of the smuggling chickens-out, Gannon has him killed and replaces him with the naive Rudy. When the guards discover a gun barrel in a newly arrived block of soap, the warden orders a complete search of the prison, including the goods warehouse. Feeling the heat, Gannon and his escape team decide to start a prison-riot the next day. Unbeknown to anyone, Gannon has a secret plan that would allow him to escape alone while the guards and the warden are busy with the rioting inmates.