Canadian Royal Mounted Police officer Louis Burke, on loan to the Los Angeles Police Department in California, is wounded when he guns down serial killer Christian “the Sandman” Naylor, who killed his partner. Sixteen months later, Burke returns to Los Angeles to meet with District Attorney Tom Vogler; Sam Walden of the State Board of Corrections; Ben Keane, who heads the governor’s task force on prisons; and attorney Amanda Beckett. Vogler informs Burke that the assistant warden and nine prisoners at Harrison Prison have been murdered. Vogler wants Burke to go inside the prison undercover as a convicted armed robber. Amanda, Burke’s “wife,” will be his only contact. Later, when Burke and other new “fish” arrive at the prison, head guard Sgt. DeGraf brutally uses his baton to display the power he has over them. Prison physician Dr. Gottesman, checking for diseases, remarks to Louis Burke that he has rare AB-negative blood. A one-eyed African-American inmate trustee named Hawkins assigns Burke his cell and prisoner number. Burke’s cellmate, Konefke, tries to intimidate him with a knife, but Burke subdues him. Later, protecting Hawkins in the chow hall, Burke kicks a Chicano gang member named Perez in the face, and as guards separate them, Perez promises revenge. Sergeant DeGraf warns Burke he will not last long. When Burke tries to join Hawkins at a table, the black prisoner tells him to sit with his “own kind.” Back in their cell, Konefke warns Burke to distrust everybody. Asked about the recent prisoner deaths, Konefke says his eyesight is too poor to see anything. On her first visit, Amanda tells Burke the prisoners all died from punctures in the back of the skull, and the latest victim was Alvin Barrett. Burke asks her to smuggle in a few $100 and $50 bills, because he needs bribe money. Later, Amanda visits Tom Vogler and his wife, Helen, who are like parents to her. They celebrate Helen’s recent release from the hospital and her new lease on life. While Burke mops the prison laundry room, Perez and an Asian martial arts expert named Bruce attack him, but he kickboxes them into semi-consciousness. Amanda smuggles him $50 and $100 bills inside the binding of a book. When Burke asks Hawkins what he knows about Barrett’s murder, the trustee sends him to see Priest in the lower section of the prison where the black drug kingpin lives in luxury with Jersey and another “woman” who take female hormone pills. After Burke gives him money, Priest suggests he talk to Alvin Barrett’s cellmate, Mayerson, who is in solitary confinement, but who also works the night shift in the prison infirmary. That night, as Burke mops the infirmary, Sgt. DeGraf and guards wheel in a new stabbing victim. Burke also sees an attendant pushing a cart full of red packages marked “Hazardous.” He “accidentally” knocks one to the floor, and learns from the attendant that it contains “medical waste.” Mayerson refuses to talk about Barrett because it could get him killed. Returning to Priest’s lair, Burke uses the kingpin’s contraband telephone to call Amanda to tell her guards are involved in the killings. Later, with the help of Hawkins,, Burke gets past a guard, slips into the records room, and finds that Barrett’s blood type is written in his file, along with the letters “SL.” Burke telephones Amanda again and puts her in touch with a high school computer nerd named Douglas Tisdale. Searching for “SL,” Douglas hacks into the prison computer and finds a file called “Sleep,” locked by the password "Morpheus," the Greek god of slumber. Douglas tells Amanda he needs another day to find more information. Later, Jersey warns Burke he will have visitors that night. Meanwhile, Douglas makes copies of a prison computer file, just as someone tries to destroy it from an outside telephone number. Amanda telephones Burke that the file contains the names and blood types of all the prison murder victims, and Burke, himself, is next on the list. That night, two guards slip into the cell, strangle Konefke with a wire, and stab Burke’s blanket with an ice pick. Burke rolls out from the hiding place beneath his bunk and knocks out the man trying to kill him, but other guards rush into the cell and charge him with Konefke’s death. Burke is dragged into solitary confinement, where DeGraf clubs and kicks him. That night, Jersey is stabbed to death and Mayerson is incinerated in his cell with gasoline. The next day, when Amanda visits Burke, DeGraf and his lieutenant, Keller, strip-search her, then take her to a “conjugal” trailer to spend time with her “husband,” who has been cleaned up and released from solitary. Amanda dresses Burke’s facial wounds as she tells him that Dr. Gottesman received his medical degree in South America and has several malpractice suits filed against him. They make love. That night, with Priest’s help, Burke and Hawkins break into an infirmary refrigerator and find human hearts and livers. The next morning, Burke sees everyone in the cellblock loudly greeting a new prisoner and is shocked to see the man is Christian Naylor, the Sandman. Later, guards ambush Burke in the shower and chain him to overhead pipes. Naylor threatens him with a knife, and gloats that every prisoner in Harrison will know Burke is a cop and try to kill him. After Naylor leaves, the guards return Burke to the general population. As he is led to his cell, prisoners threaten him. Meanwhile, Amanda goes to Tom Vogler’s home to tell him they need to rescue Burke immediately. At that moment, Douglas telephones to tell her he found the outside telephone number of whoever tried to erase the computer files. When he gives her the number, she realizes it belongs to Vogler. When she confronts him, Vogler explains that he could not get his wife, Helen, a heart transplant in time because she was too far down the list. However, Dr. Gottesman found a heart and arranged for the secret operation that saved her life. Now they are making money harvesting organs from prisoners. He admits that he arranged for Naylor, the Sandman, to be transferred to Harrison Prison, in order to get rid of Burke. At that moment, Helen enters the room, and Amanda reveals that her husband murdered for her. At the prison, Burke wires the bars of his cell to a battery and amplifier, so that when Keller, the night guard, grabs them, the electric shock knocks him unconscious. Taking Keller’s keys, Burke escapes. Naylor hurries to the main switch that controls all cell doors and lets the prisoners out to chase the cop through the prison. DeGraf hits Burke with a club and, with another guard, drags the undercover Mountie to Dr. Gottesman’s infirmary, but Hawkins blows open the door with a shotgun. He and Priest rescue Burke and run. Behind them, prisoners capture Dr. Gottesman and tell him he is “just in time for surgery.” His screams echo through the prison. Hawkins is wounded, and Priest shoots DeGraf. As they hurry to a boiler room, Naylor kills Priest and goes after Burke with a wrench. As they fight, prisoners gather on tiers above them to watch. Burke kicks Naylor into a burning furnace, but he stumbles out in flames and extinguishes them by rolling on the floor. Burke kicks Naylor into a bolt in the wall, which penetrates the back of his skull. The prisoners allow Burke to walk out, carrying the wounded Hawkins to a waiting ambulance. Amanda embraces him, as police arrive at the prison.