[The following plot summary is based on the English-language version of this film, The Big House ; character names refer to that version.] Kent Marlowe, a frightened young man convicted of manslaughter while driving drunk, becomes cellmates with hardened prisoners "Machine Gun" Butch Schmidt and John Morgan, who are serving time, respectively, for homicide and robbery. Conditions at the prison are extremely harsh, especially in the prison mess, where the convicts are fed small amounts of spoiled, inedible food. One day, when Butch loudly objects to the food, causing an unruly outpouring of complaints from the other prisoners, Warden James Adams orders him to be placed in solitary confinement, called "the dungeon," for thirty days. Before he is taken away, Bush passes his contraband knife down a row of prisoners until it reaches an anxious Kent. When yard snitch Oliver later tells Kent that his time in prison could be significantly shortened if he passes on information to the guards, his naiveté and fear cause him to hide the knife among Morgan's things. When head guard Wallace searches Morgan's bunk, he finds the knife and sends him to the dungeon, even though Morgan was to be paroled the next day and swears that the knife is not his. At the end of his time in the dungeon, Morgan feigns unconsciousness and is taken to the prison hospital. Late that night, by sneaking away from his hospital bed and changing places with the corpse of another prisoner who has just died, Morgan is able to escape the prison in the mortician's wagon. Intending to get back at Kent, whom he deduces planted the knife, Morgan goes to a bookstore owned by his sister Anne, whom Morgan had briefly seen visiting Kent in prison. Although Anne recognizes Morgan, when a policeman acquaintance, Sgt. Donlin, comes into her shop while Morgan is there, she covers for him, saying he is an old friend named Everett. Morgan starts a job and begins to spend time with Anne and her family, and the two fall in love, but his freedom is short-lived when Donlin, who had recognized Morgan, arrests him at the Marlowes' home. Back at prison, Morgan determines that he will serve his time and start life over when he is released. Butch wants Morgan to come with him, Kent and some of the other prisoners who are planning a prison break, but Morgan refuses, saying that he plans to go straight, despite the wretched food and horrible conditions at the prison. On the day of the planned escape, just before noon, when the attempt will be made, Morgan is called into the prison office. When Butch and some of the others start to break through the prison gates, which were momentarily opened to allow fellow conspirator Gopher, the prison gardener, hand a bunch of flowers to a guard, they are greeted by Wallace's men firing machine guns at them. Butch is convinced that Morgan had revealed their plans, even though Morgan refused to give Wallace any information. Unknown to Butch, Wallace has confirmed to Morgan that Kent is the informer. After some of the prisoners are killed in the escape attempt, Butch and his remaining cohorts barricade themselves inside a cellblock and, using prison machine guns they have confiscated, threaten to kill all of the guards they have taken prisoner. Morgan risks his life to save some of the guards, despite being wounded. As tear gas canisters and finally an army tank enter the cell block, a panicked Kent is killed. Butch, who has been mortally wounded, is about to kill Morgan when one of the other prisoners reveals that it was Kent who was the informer. As he dies, Butch smiles at his friend, saying he would never kill him and was "just kidding." After the riot is quelled, Morgan is proclaimed a hero and pardoned by the governor. He promises Adams that he will go straight from now on and plans to move to the islands or another country where government lands are available. As he leaves the prison gates, Morgan is embraced by Anne, who has been waiting for him.