This slice of prison life is quite realistic, though real prison inmates rarely experience such a crescendo of violence as found in the movies.
Kent Marlowe (Robert Montgomery) got ten years for manslaughter while driving drunk The warden explains that they have to put him in with hardened criminals because of the overcrowding. He notes that people want criminals put away, but they are not willing to provide the facilities. He expects that someday they will have to pay for their shortsightedness. Kent learns about Butch (Wallace Beery) right away as the tough guy takes his cigarettes, though Morgan (Chester Morris) gets them back for him. Butch gets sent to the "dungeon" for inciting a protest in the dining hall, and his knife gets passed to young Kent, who puts it on Morgan's bunk. This results in Morgan losing his parole and going to the dungeon too. Morgan plays sick and escapes by taking the place of a corpse. He finds Kent's sister Anne (Leila Hyams); fearing he is out for revenge, she is about to turn him in but changes her mind. He gets a job, and they become friends; but Sergeant Donlin tracks him down and arrests him at her house.
Butch is planning a prison break for Thanksgiving day, but Morgan refuses to join. Kent is in on it but has turned stool pigeon to get his sentence cut in half. Machine guns are waiting for them. Butch starts killing guards they have taken hostage; but Morgan manages to lock the hostages away. Butch goes looking for Morgan. As army tanks are breaking in, Kent, terrified and racked with guilt, admits he "squealed" and is killed. Butch and Morgan shoot each other. Butch dies; but Morgan, only wounded, is freed for his heroism.
This archetypal prison story shows the hellish prison life and how its social relationships are distorted as the inmates have their own code of ethics. The inexperienced Kent badly violates this and comes to a bad end. Butch is a habitual liar and cheat and so has little hope. But Morgan shows how one can overcome the odds and rise out of a dismal situation. Although he escaped on his own, he refuses to participate in a violent and foolish attempt. He is not a stool pigeon, but he saves the lives of the guards. If there is any rehabilitation, it is by the individual's efforts in spite of this dismal prison system.