Plot

A tough prosecutor who has sent dozens of criminals to prison finds himself framed on a bribery charge and winds up in prison himself.

Steve Donegan (Walter Pidgeon), finishes examining a witness and returns to his office for lunch. Three reporters wait for him at his door wanting information on an indictment Donegan is seeking for racketeering at the Teleflex corporation. Steve reveals that he his flying in a star witness to be heard by the grand jury before he is summoned back to court. As Donegan delivers his closing summary to the jury, Anne Barry (Rita Johnson) insists she is victim of a frame up in the embezzlement case, which Donegan says is impossible in the court system because of all the perjured testimony that would be required. With his 500th conviction, Donegan wins the election for district attorney and begins a war on organized crime. Crime boss Joe Silenus (Harold Huber) has taken notice and bugs Donegan dinner table while he is dining with Dan Barrett (J.M. Kerrigan), a former aid. Steve and Dan discuss the deferment of a case involving one of Silenus's front men for land swindling. Barrett, however, owes money to Silenus because of his gambling habit. Silenus agrees to pay off the money Barrett owes to Donegan with a check he endorses over from Silenus' syndicate. Then Silenus plans to frame the payment as a bribe they made to Donegan so that Silenus' front man is not prosecuted. Donegan is arrested for accepting a bribe. With Barrett's testimony as a go between, Donegan is sentenced to prison for 1 year. Steve's younger brother Phil (John Arledge) is released from him job as a prosecutor. Steve encourages him to lay low until he is released rather than pursue Silenus on his own, Steve is sentenced to prison where he again meets all the men that he convicted in his anti-crime crusade. Silenus sends one of his men to the prison to give word to 'Socks' Martin (Nat Pendelton) to eliminate Donegan if the prisoner population does not take care of him on its own. Word spreads quickly in the prison of Steve Donegan's arrival. Prison doctor Malcolm Scott (Paul Kelly) warns Warden Parkhurst (Grant Mitchell) that Steve will be a marked man by his six thousand enemies, but the ineffectual warden refuses to offer Steve special protection. Even as he enters the prison, some prison workers accidentally drop platform from their work above narrowly missing Steve. When an inmate tries to stab Steve, Anne Barry, the woman he convicted of embezzlement, saves his life by warning the guards with her screams. As Dr. Scott dresses his wound, he warns Steve that some prisoners have handguns that have been snuck into them. To keep him separated from the general population, the doctor assigns Donegan to the prison infirmary where the elderly and lunatic prisoners are housed. 'Socks' Martin gets his instructions to eliminate Donegan. He injures his cellmate, so he can gain access to the prison infirmary. Steve is terrorized at nightly by the man in next bunk Bluebeard Dawson (Arthur Aylesworth) who killed seven wives. Eventually Bluebeard becomes Steve's ally, Steve's brother Phil begins to tail Silenus dressed as a chauffeur determined to prove Steve's innocence. One day, while Steve is fixing a pipe in the prison laundry, he talks to Anne Barry. She again claims she was framed. Steve argues this his case was political rather than criminal. Another inmate called 'Peachie' (Helena Phillips Evans) scratches Steve when he tries to make Anne understand. Later, Steve reconsiders his opinion of Anne's case. Steve drops a note to Anne as he is running a plumb line against the waterpipes offering to help her with her case. In the note, he requests Anne write out every name and fact she can remember. Anne returns his letter dropping it in the laundry room piping. Donegan requests the doctor return him to the general population. The doctor agrees to allow Donegan to join the other men in the dining hall. As Donegan seats himself, a chant of "Donegan" grows across the hall. After several prisoner threaten Donegan and a prisoner worker serve the soup in Donegan's lap, a riot erupts, and the prison guards fight off the inmates to save Donegan. For his part in the riot, Donegan is given two weeks in solitary confinement. Meanwhile, Phil is spotted by Silenus outside of the Chapin & Graham Company. When Donegan is released from solitary confinement, he sees a poster that he is scheduled to box 'Socks Martin' for 10 rounds the following Saturday. At first, Donegan protest the fight to the doctor, but the doctor says the fight will gain Steve the respect of the inmates by showing his courage. Steve resolves" to get that lug if he can." In the first round, Martin charges and swings wildly, but Donegan uses boxing skills to fend him off. In the second round, Steve knocks 'Socks' down, but from that point on, 'Socks" owns the fight, knocking Steve down six times, but Steve continues to get up and resume the fight. Nearing the end of the fight, Steve is knocked down two more times and gets up before he collapses on his own. He has, however, earned the respect of Martin and the cheers of the inmates. As Donegan recuperate in the prison hospital, several prisoners stop by to show their appreciation. Among them is 'Socks' Martin who tips him off that there is a prison break coming and that someone will try to kill him inside or when he gets out. 'Socks' advises Steve to join him in the prison break. Two revolvers are smuggled into the prison inside a basket of fruit intended for the prison warden. As Steve is mending in the hospital, he asks the doctor for a visit from Anne Barry but is denied by prison rules. A short time later, however, Anne shows up when she is summoned to room 309 on a work detail and Steve is able to show her a letter from his brother. The information in the letter ties ins with Joe Silenus and with both the lawyer that supposedly defended Anne and the jewelry store who was the chief witness against her. When Phil arrives at the prison to visit Steve, he is shot in a drive by shooting just outside the gates A truck blocks the murderous car's path and a violent gun battle ensues between the car's occupants and the prison guards stationed above. The shots send the prisoners into a riot and the rumored prison break begins. Phil dies in the prison hospital, and an engaged Steve seeks to join the break. The doctor tries to stop Steve, but Steve decks him and heads outside. Several prisoners including 'Socks' Martin take Dr. Scott hostage. Steve plans to escape, but after the convicts take Dr. Scott away, Anne convinces Steve to stop them. Steve prevents Martin's escape by pumping steam into a passageway leading to the unguarded back gate. The men are scalded trying to escape. Reinforcements arrive and quell the riot. With the evidence that Phil uncovered, Steve is exonerated, and he returns to his post of district attorney to clear Anne and send Silenus to the electric chair. Anne and Steve look at a model of their future home