Things get a bit lively on death row after Shirley Bellinger's execution-- Miles begins painting a self-portrait, Ginzburg's health deteriorates from AIDS and Deyell severely injures himself. Mobay's ordered to kill someone as a final test of his loyalty and a new prisoner, whom Mobay's familiar with, makes the perfect victim. A call stirs McManus' emotions again. New inmate Supreme Allah arrives creating tension and uneasiness for Arif. On his way to his son's funeral, Beecher asks Keller an intimate question. A changed Rebadow asks for permission from Morales to kill again. After a fight with the gangsters, Cyril's put on heavier sedatives. For Ryan O'Reilly, he gets the cell phone after ratting to Hoyt and he also meets Dr. Nathan's attacker.

In the Season Four finale, Hill discovers where his true allegiances lie. Redding's plot to use the Colonel against Morales has an unexpected outcome. Cloutier runs into trouble from his church on the outside and his parishioners in Oz. White gets a little too close to McManus. Beecher's agony about his parole hearing leads to a shocking climax.

Three generations of Alvarezes—all prisoners at Oz—are united when the partiarch, Ricardo, is found face down in his cell, suffering from Alzheimer's disease. Meanwhile, Beecher, who as Schillinger's "prag" has been forced to wear women's clothes, flips out after taking PCP.

The kidnapping of Beecher's children has everyone upset and Beecher inconsolable. Schillinger gets questioned and of course, claims to know nothing about the deed. Beecher decides to initiate his own investigation. Soon after, a package with horrendous contents arrives for Beecher. Meanwhile, Oz prepares for Shirley Bellinger's hanging as the death penalty protests continue. A visit from the Cardinal creates mixed feelings for Sister Pete and Father Ray. Said announces good and bad news in the state's decision for the inmates. Another Rebadow prediction comes chillingly true. O'Reily's still searching for that elusive cell phone and Dr. Nathan asks Glynn for permission to return to work earlier than expected.

A ribbon cutting ceremony, complete with the Governor doing the honors, signals the opening of a newly constructed Oz. Warden Glynn doesn't resign but he's more battle weary. White, Alvarez and other inmates in solitary are temporarily transferred to Em City while repairs are being made. As Schillinger and Robson recover from their wounds, they begin planning revenge on the Muslims. Conversely, Said plans to plead guilty for the attempted murder of Robson & Schillinger. The fate of Rev. Cloutier is revealed and inmates expecting visits from family members get shocking news.

In the "Emerald City" experimental unit of Oswald State Penitentiary, we meet some of the diverse inmates who live within a pecking order of Homeboys, Latinos, Muslims, Irish, Aryans, and Wiseguys. No clear-cut leader emerges—with the possible exception of Kareem Saïd, a Muslim author who preaches non-violence and abstinence. Saïd's arrival doesn't prevent a short-fused Mafia inmate named Dino Ortolani from ticking off just about everybody—a habit that ends up burning him.

Beecher is released from the hole and Schillinger is left eyeless and weak. A riot breaks out after two white punks get into a fight over checkers. Frustration, sexuality, hate, revenge, racism all rear their ugly heads, causing the violence to escalate.

A recovered Saïd ostracizes Mershah for turning his back on him when he was dying—and orders the rest of the Muslims to do the same. Impressed by Saïd's power, Groves makes a deadly decision in his honor. Meanwhile, Beecher, transformed by prison life, finally gets revenge on Schillinger.

Robson and Hoyt tell Rev. Cloutier to back off of Schillinger. Schillinger and Beecher have their first counseling interaction session. Tidd continues to get close to Said by defending Arif in a fight. Arif goes to Said and pleads Tidd's case to accept him into their Muslim group. Busmalis requests that he and his girlfriend be married. Glynn hosts the Warden's conference and is given an update on Hughes by Querns. Glynn soon has Hughes transferred to Oz's cops unit so he can protect him. This unit is also where Johnny Basil (Mobay) is locked up. Keller's old buddy Ronnie gets close to Beecher causing Keller to get jealous. Ronnie's offered a sentence reduction in exchange for corroborating evidence of Keller's involvement in some past murders. Beecher finds this out and warns Keller, who doesn't believe him. Keller question's Ronnie about the matter and then, comes up with his own solution. Em City inmates are selected for drug testing experiment that promises to age the person quickly therefore reducing their actual time spent in prison.

Schillinger has a disappointing visit with his "hero", Mayor Loewen. Glynn has to face up to the truth when Oz loses its first prisoner to toxic poisoning. Down in solitary, Officer Brass gets some quality one-on-one time with Morales. Cyril undergoes a round of unusual therapy, and Said gets more than he bargained for in leading the Muslims into a new business venture.

Three new inmates arrive, one of whom is close to the O'Reilys; Busmalis and Rebadow prove to be "true Romeos"; the Keller-Beecher-Schillinger triangle gets more pointed; and an awards banquet ends in a fateful discovery.

The infiltration of drugs into Oz has reached unprecedented levels, and the undercover efforts of McManus and Glynn to find out who's smuggling them in backfires in a deadly way. Despite a lockdown in Emerald City, the drugs continue to trickle in—and the blame shifts from prisoners to corrupt officials.

With Schibetta and the prison brass in a race to uncover Ortolani's killer (for very different reasons), we see how inmates react to visits from both their wives and, in one case, family members who are also in prison.

Wittlesey is transferred to Gen Pop and replaced by Karl Metzger, a Nazi. Mack and another Aryan try to escape through Busmalis and Rebadow's tunnel but the tunnel collapses and kills the two Aryans. Hill gets the idea of escaping Oz by hiding in a coffin. Sippel re-enters Oz because he can't deal with life on the outside, but Schillinger crucifies him -- literally. Alvarez gouges out Rivera's eyes and is put in solitary for life. Needing a blood transfusion for Rivera, Dr. Nathan finds that only O'Reily has the same blood type; he agrees to donate in exchange for getting his brother Cyril near him. Keller and Schillinger reveal their sordid plan of deceit to Beecher while breakingv both his arms and legs. Fortune teller Kipkemei Jara gives Adebisi hope of a new life; but he is murdered by Wangler on orders from Antonio Nappa. The grief this causes Adebisi lands him in the psych ward. Said is pardoned by Governor Devlin, but refuses choosing to return to Em City instead.

Alvarez and Guerra come up with a new way to settle their beef -- Guerra will stab Alvarez in the shoulder without killing him. Morales questions Guerra's decision to do this while he attempts to grieve for his sister. Rebadow gets more bad news about his grandson which prompts him to search for alternatives. Montgomery asks for more hush money from Ryan so Ryan devises a plan to have Montgomery eliminated. Officer Brass returns to Oz to get facts on who attacked him. Ellie O'Connor arrives as the Governor's liaison to Oz only past memories of her failed marriage to McManus return. Schibetta returns and Schillinger shanks Pancamo after learning that he had Hank killed. McManus makes an offer to Said and White to hopefully curb White's erratic and sometimes bizarre behavior. Ryan's mom, Suzanne Fitzgerald comes to Oz to instruct inmates in performance arts.

Robson returns from solitary to discover he's been kicked out of the "Brotherhood" and moved to another cell. McManus tells Glynn he'll write a letter supporting Alvarez's bid for parole. Problem is, Alvarez attacks one of the parole board members and gets thrown back into solitary. Dr. Nathan's guilt worsens as Chucky slips into a coma from the septic infection. Schillinger tells new inmate Cutler he has to kill a black inmate to join the "Brotherhood" and Cutler selects Said as his victim. White's gets this information and goes to protect Said only they get into a tussle and Cutler almost dies. Rebadow gets to go see his dying grandson only to have to return later for the boy's funeral. Busmalis gets a letter from Norma who wants to visit. She does and brings surprising news. Beecher moves to make a confession during the interaction session. The result? Schillinger gets convicted of rape and is transferred to solitary indefinitely. Father Meehan touches a nerve with Ryan and forces him to acknowledge a childhood incident that scarred Ryan for life. A stabbing intended for Redding, claims an innocent inmate instead.

With their enmity at a boiling point, Adebisi poisons Schibetta -- but not fatally. Now that his brother has turned himself in for murder, Glynn no longer owes Schibetta any favors. Sister Peter Marie figures out that Giles witnessed who killed her husband. Poet, now a published author, gets his parole, but Governor Devlin still takes away funds from McManus's high-school equivalency program. When Beecher learns his wife committed suicide, Keller offers comfort, but his advances are rebuked. Meanwhile O'Reily is in love with Dr. Nathan, and gets his brother Cyril to have her husband killed.

As friction grows in the wake of increasing deaths, Schibetta, Saïd, and Keane are brought together by Glynn, who tells them to keep their respective groups quiet or else he'll lock the prison down. The tension increases following a visit from Governor Devlin, who was responsible for the ban on smoking and conjugal visits.

Governor Devlin has reinstated capital punishment in the state, and the first Oz prisoner scheduled to die is Keane.

In addition to the name change to "Oswald State Correctional Facility," more changes abound. Newbies Coyle, Kahn, and Ricardo arrive and partner up with Wangler, Said, and Hernandez respectively. Adebisi's "recovery" prompts a return. Clayton Hughes, son of a past Oz guard who came through the ranks with Glynn, asks Glynn to hire him. Meanwhile new Officer Howell, gets friendly with McManus. A managed health care company takes over Oz's infirmary, to Dr. Nathan's disgust and Alvarez's detriment. Cyril O'Reily still has nightmares about being raped by Schillinger and Ryan schemes on revenge. Said develops an unlikely alliance as he starts a hunger fast in response to McManus rejecting his request for food in his cell during his holy season. Keller confesses his part in setting up Beecher and is immediately taken into protective custody. Beecher gets some oh-so-sweet revenge.

Glynn receives some good and bad news on the toxic-poisoning case. Meanwhile, Rebadow's relationship with Stella hits a snag; Keller and Beecher work out a mutually beneficial arrangement; Poet and Redding nearly come to blows; Hoyt is transferred from Death Row; and Robson finally gets some redemption.

Said returns from the hole ready to apologize to White. The inmate variety show takes shape with Busmalis as MC and White the featured performer. Robson's painful teeth force him to the dentist, something he secretly fears. The dentist recommends gum replacement surgery. Alvarez wants to give his dog to Rivera the Oz guard he blinded. Cyril's trial looms and Ryan's worried. Redding continues to search for culprit that gave Hill the drugs. Poet, in an attempt to hide the truth from Redding convinces Busmalis to tell Redding that one of the Italians did the deed. This results in Redding having DeSantos poisoned. Chucky's condition worsens and out of fear, he summons Sister Peter for spiritual help. Meanwhile, Sister Pete starts looking for Guenzel's attackers only the 3 who know (Said, Beecher, Schillinger) refuse to divulge.

Cyril O'Reily, Ryan's brother comes to Oz and is immediately violated by Schillinger. Ryan tries to get him away from OZ, but Cyril instead lands in the hole. El Cid tells Alvarez the only way he can "stay in the game" is to "pluck out" the eyes of a prison guard, Rivera. Bellinger and Adebisi exchanging love letters without meeting. Nappa, the new Wiseguys leader, wants Adebisi to be punished for raping his godson Peter Schibetta. Robert Sippel, a Catholic priest who spent ten years in OZ for molesting a 14-year-old boy is released and but Poet returns.

O'Reily regrets getting Cyril involved with the trial drug when it starts taking effect. Meanwhile, Giles's request for an unusual method of execution creates controversy and the Chinese refugees are deported...but not before plotting revenge on Morales.

McManus finds he is unable to turn his back on White. Beecher tells the parents of the young girl he killed that he's up for parole. Howell tries to blackmail O'Reily so she can get to Cyril, but he throws her for a loop--and then O'Reily is thrown himself by a family secret.