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.

After Hughes's attack on Devlin, Glynn withdraws from the race. Alvarez is still on the loose. Supreme Allah gets an unwanted surprise.

Idzik faces his enemies; the intrigues behind the Loewen case get more complicated; changes are made in the hospital; the Muslims run into business trouble; Rebadow and Stella get closer; and the inmates rally to support the O'Reilys.

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.

The lockdown ends. After Hamid Khan's body is taken off life support, the Muslim's choose Arif to lead them. Meanwhile, Cyril's having nightmares about delivering the fatal blow to Khan in the boxing match. Ryan asks Sister Pete to intervene. Murphy makes a suggestion to help ease some of the strain in solitary after another inmate commits suicide. Father Mukada plants an inventive idea in Beecher's head on how to deal with Schillinger. Shirley Bellinger returns awaiting her date with the noose. New inmate Mobay, arrives to Oz and his cellmate Hill is immediately suspicious. Gov. Devlin invites Glynn to be his running mate in the Gov's re-election bid. McManus gets an update on Wittlesey, who hasn't returned from vacation and a shootout in Oz results in four deaths.

Ryan and Howell get frisky. After leaving the hole and apologizing to Busmalis for the stabbing Rebadow suffers an attack due to a brain tumor. Busmalis reacts by doing what he does best--start another tunnel. Unbeknownst to the doctors and everyone else, Cyril's recovering psychologically more than he can actually show. Arif confesses to Said about his own demons and asks for forgiveness and help. Said plots with McManus to end Querns' and Adebisi's control. Hank Schillinger beats the kidnapping rap and once Beecher finds out, he plots with Pancamo for revenge. After Keller reveals his plot to kill him, Eli Zabitz asks Schillinger for protection. Schillinger agrees but sends Robson to eliminate Zabitz instead. Hughes, now raging beyond sensibility, makes an attempt on Devlin's life at a press conference. Keller and Father Ray have an intense discussion about Beecher.

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.

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.

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.

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.

Oz is in upheaval following the return of Martin Querns. Meanwhile, Howell and Robson each receive troubling news, Mukada answers an unsolved mystery, and the O'Reilys struggle to make amends. Finally, the prison production of 'Macbeth' ends with a staggering final act.

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.

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.

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.

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.

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.

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.

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.

Andy Schillinger arrives to Oz and Vern tries to get Warden Glynn to move Andy in with him. McManus is sued for sexual harassment. Sister Pete has questions after a session with Keller. Miguel gets a directive from Hernandez. Said gets old wounds opened when his sister visits. Ryan scores another victory. Officer Hughes makes a "stunning" move on an inmate and Richie Hanlon's death sentence is overturned.

Sister Pete's anger is roused and forces her to confession. Wangler and Adebisi register a complaint to the Warden. Yet another inmate meets with demise. Bellinger enlists McManus' help. Glynn and Hughes have an important conversation. Adebisi begins sowing seeds of discontent and a fight erupts in the gym resulting in a lockdown.

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.

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.

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

With a new day breaking, Officer Howell makes a gruesome discovery. Dr. Nathan takes action against medical official Garvey. Ricardo and Hughes have a brief confrontation that results in a reprimand. Said's attorney brings good news and a special delivery. Richie Hanlon explains to Shirley Bellinger why he's on death row. New prisoner Stanislofsky joins the fold. Each group in Oz prepares their boxer for upcoming matches. Hill returns from testifying against Coyle, and the jury's still out as to whether or not that was the smartest move. Said solicits assistance from Nappa, Schillinger and Guerra. Nappa turns over control to Pancamo after discovering he has a debilitating illness.

After getting pummeled by Khan in a boxing match, Kenny discovers his wife's infidelity and arranges a contract. Miguel prepares to meet his victim face to face. McManus' lawsuit starts taking it's toll as he wrestles with settling or going to court. New inmate Kosygin is mysterious at best and Stanislofsky keeps a safe distance. Busmalis gets a surprise in the mail. Hughes presses Glynn for more information about past deeds. Beecher and Andrew form an alliance that angers Schillinger and Poet and Junior get a hot reception.