Sabrina Downs narrates an experience that she had while serving time as a convict in the Whitehead Correctional Institute. Her story begins as she meets Frances Shephard, a timid woman that is new to the prison system, during their bus ride to the correctional facility. The women arrive at the prison, where they meet Captain Alan Dease, who proceeds to line them up and exclaim the rules of the prison and consequences for not abiding by them.
As Frances is escorted by an officer to the jail cell she will be living in, she enters to a scene of female convicts gambling, smoking, and talking amongst themselves. She attempts to move in with her cellmate Nikki Barnes, who is presumed to be the leader amongst the convicts, but is denied and instead lives with Lil' Mama, a 17-year-old pregnant convict who is deeply involved in Christianity and befriends Frances. Lil' Mama introduces Frances to another inmate named Wet, who informs her on the different crews in the prison. When asked what crime she committed, Frances confesses that she accidentally murdered her abusive husband in an effort to protect herself. The next day, Frances is familiarized with the inmates' daily routine of hard labor in what the other convicts refer to as a "sweatshop".
Michael Meadows, a law student who is hired as the new correctional officer at Whitehead, enters Dease's office and introduces himself. They have a brief conversation before Dease is called to stop a fight that has occurred between Nikki and Aisha, who the other inmates claim to be Dease's secret mistress and informer. After two officers take Aisha away for starting the fight, Dease has an intimidating conversation with Michael, informing him that he runs the prison, not Nelson, the warden. Nelson approaches Dease and they collaborate about their plans to increase their profit off the prison.
Aisha enters Dease's office to discuss her fight with Nikki and Dease slaps her in the face, telling her how unimportant she is. He presents Aisha with a gift, but refuses to give it to her until she provides him with any information about the other convicts. Dease then turns off the surveillance camera and forces Aisha to perform oral sex on him. After she leaves the office, Aisha finds Frances, punches her in the face as reprisal for confessing that Aisha caused the fight, and steals her necklace. Aisha leaves around the corner and is surprised by Nikki, who stabs her and takes one of Frances' necklace back. After the incident, Michael takes Frances to Dease's office where Nelson questions her, but Frances provides no information about what she saw and is let go. Later that night, Dease and the other officers enter Nikki's cell and beat her, claiming that they know she stabbed Aisha. According to Sabrina's narration, however, Dease secretly loves Nikki and abuses her because she does not return the feelings.
Michael enters the break room where Dease and the other guards are. They begin to discuss the possible closing of the prison and John Banks, a white officer, is concerned about finding a new job. Dease claims that the loss of jobs is associated with untrained students, such as Michael, stealing their jobs, which creates tension between the other officers and Michael. As Michael attempts to defend himself and the mistreated female inmates, Dease proceeds to yell at him that these women have no respect for society and therefore, deserved to be treated poorly. Later, Michael does his own research on the prison system and discovers that these female convicts are being exploited for cheap labor.
At night, Lil' Mama becomes very ill and the other convicts are concerned about her and her child's health. No officers come to help and Frances, who was a nurse, takes care of Lil' Mama throughout the night. During that night, Frances has a connecting conversation with both Nikki and Wet about why they were in jail. Wet shot a track runner who was sleeping with her boyfriend/husband in broad daylight and in front of 12 witnesses. Frances is then asked why she is in there and she explains that her husband was beating her, so she had finally had enough and shot him, landing her in prison. As Wet argues Frances' innocence, Nikki comments on why she was locked up for protecting herself. The next day in the sweatshop, Nikki thanks Frances for helping Lil' Mama and returns her necklace. The ladies receive bad news that Frances was denied an appeal, Nikki's children would not come to visit, and Wet gets a citation for creating a petition to end the prison's harsh working conditions. Also, Aisha returns after recovering from being stabbed. She and Nikki have an exchange of words when Aisha makes an insulting comment about Nikki's mother, tempting Nikki to fight her but is quickly broken up by close guards.
Frances, Nikki, Wet, and Lil' Mama now friends, sneak off to the kitchen where they share food and wine. They witness Dease secretly place a small bomb in the kitchen which goes off and alarms the other officers. As a result, Dease blames the incident on the inmates and has the kitchen rebuilt. After placing the prison on lockdown, Nelson approaches Dease, angry about the explosion and Wet's petition. Nelson states that he was informed that Dease created the explosion and threatens to fire Dease if he attempts any secret plans again.
During a cell search, Officer Banks enters Wet's room and begins to damage her belongings, causing an altercation between Wet and Banks and Wet being taken to solitary confinement. When she returns, Wet and the other inmates collaborate and create another petition in a few days to present to Miller, a man that Nelson hopes will invest in the prison's cheap labor. When Miller arrives to the workstation where the inmates are, Frances stands and reads the inmates' demands for better working conditions and Nikki proceeds in giving the petition to Miller. Dease and Banks begin to hit Frances and Nikki and take them to solitary confinement where they stay for 6 days. During this period, they share stories and Frances helps Nikki overcome the temptation of snorting the cocaine that Dease takes to her room. They are let out and return to their routine. During a visit from her sister, Frances discovers that her daughter Maxine has been killed in a gang shooting.
After returning from suicide watch, Frances and the other inmates devise a plan to get back at Dease with the help from Michael and Aisha, who is fed up with Dease for beating her. While Lil' Mama cleans Dease's office, Aisha enters and seduces Dease, who kicks out Lil' Mama and turns off the surveillance camera. After Lil' Mama returns briefly and turns the camera back on, Aisha makes it appear as if Dease is raping her. Caught on video, the ladies plan on giving the evidence to the governor. When Lil' Mama attempts to take the tape in Dease's office, Dease harasses and rapes her. When she returns to the jail cell, bleeding profusely and in terrible pain, the other inmates rush her to the infirmary where she suffers a miscarriage and dies. The inmates, who are violently upset, attack the doctor as he attempts to call Dease to have them escorted back to their jail cells. They hold the doctor at gunpoint and handcuff Michael to a chair. Wet shoots Dease as he enters and he in return fires a shot and hits the doctor. Nelson, informed of the situation, refuses to call the governor for assistance and instead orders the officers to be ready at the scene. In the infirmary, the convicts release Michael, handcuff the wounded Dease, and call Nelson, telling him he has one hour to get the governor on the phone. Nelson demands to speak with Dease in order to ensure that he is alive. The inmates put Dease on the phone and force him to tell Nelson that he raped Lil' Mama. When her back is turned, Dease attacks Frances and Nikki shoots Dease several times, killing him and avenging Lil' Mama's death. Sergeant Cervantes, the officer in charge, orders the inmates to surrender and Wet goes outside and kills an officer, after which Wet is shot and killed. After much thought, Frances and Nikki decide to exit the infirmary and they are killed by the officers.
Meanwhile, Aisha sneaks into Dease's office and retrieves the tape. During her final narration, Sabrina explains that after taking the evidence to a lawyer, the women file a lawsuit against the prison for their abuse and win the case. The prison is shut down and Nelson is indicted for making corrupt business deals and using the prison for his profit. Aisha is killed in a prison fight shortly after. Sabrina, now free, dedicates the inmates' victory to Nikki, Frances, Lil' Mama, and Wet for their courage.
