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.

Mobay has his first meeting with Adebisi. Glynn fires McManus after Tim makes a foolish outburst during the slain CO's memorial service. Sister Pete still wrestles with ending her service as a nun. Beecher's dad pays a visit and gives an update. Schillinger is visited by his other son, Hank. Said's decision to help Cramer secure a new trial is met with strong opposition by the Muslims. Poet grieves and ponders his next move now that Wangler and Pierce are dead. O'Reily's plan to get the cell phone backfires and results in another inmate's death. Bellinger returns to Oz to await her impending execution.

All is crazy after Busmalis and Alvarez flee from Oz via one of Busmalis' tunnels. Hernandez discloses details about the shooting to Glynn and mentions Tarrant getting the gun from Adebisi, who got the gun originally from Clayton Hughes. Glynn confronts Hughes, Hughes confesses immediately and is quickly arrested. New inmate Morales is offered Hernandez's end of the "tit" trade only if he kills Hernandez. Morales asks Rebadow to do the deed in exchange for anything Rebadow wants and Rebadow accepts. Escapee Busmalis is caught and returned to Oz where he is rebuked by Rebadow. A "fresh from the hole" Adebisi begins implementing his plan to get a new Em City administrator. A cell phone appears and Ryan schemes to get his hands on it. Like most O'Reily schemes, someone ends up dead and this case is no different as Hoyt's recruited to do the "honors". Said scores a victory for Jason Cramer and Shirley Bellinger gets a visitor.

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.

An investigation into Goergen's death starts and Mobay's anxious when the investigator targets him first. Tensions begin to rise as Querns turns a seemingly deaf ear and blind eye to the blatant violations committed by black inmates. An inmate transfer works in Adebisi's favor. Arif challenges Querns's authority. Ginzburg's poor health forces him to request an early execution and Sister Pete convinces Glynn to make it happen. Glynn's press conference announcement forces his daughter to make a major decision. Beecher's daughter arrives alive and Keller confesses to Mukada.

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.

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

Adebisi's death still looms large over Oz. Against Glynn's better judgement and with special permission from the Gov., a TV news crew comes to Oz to film. Ryan O' Reily recognizes the star reporter as a past enemy and he immediately embarks on revenge. After interviewing inmates -- including Poet who strongly suggests the cover up can be exposed through Adebisi's video tapes-- the show's producer gets busy digging for answers. McManus discovers this and immediately tells Glynn to destroy Adebisi's tapes or face Oz possilby being shut down. The star reporter moves into a pod with Cyril for the evening to catch a "verite" view of Oz. The stunt backfires as Cyril (with prompting from O'Reilly) brutally beats the reporter.

New inmate Burr Redding arrives and stands ready to assume control of the drug business. Dr. Nathan returns. Tidd approaches Schillinger with a plan to kill Said. Several Asian refugees are housed in Em City while the government decides their fate and they unwillingly get caught in a power struggle between Morales and Redding. Glynn hires an energetic new assistant who piques everyone's interest.

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.

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.

O'Reily is in for a surprise when a visitor reveals the truth about his past, while Cyril faces trouble for his difficult behavior. Meanwhile, Morales and Redding lay out plans that could lead to all-out war in Em City.

McManus calls a superficial truce between Redding and Morales. Basil finally sees his wife, but Hughes ends up spoiling their happiness. Meanwhile, Cyril's latest outburst proves to be the last straw.

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.

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.