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.

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.

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.

After the press conference shooting incident, Glynn pulls out of the race. When a corpse is found in the laundry room, Querns demands Adebisi find out who did the deed. Soon Browne's corpse is also discovered and Querns gets worried. Querns's investigative efforts point to Supreme Allah as the culprit only Supreme's really being framed for the two killings by O'Reily and Keller. Hill pays big when he tells Mobay he knows he's undercover and Mobay comes clean about his involvement in Oz's recent crimes. Considering the words of Cyril, Sister Pete decides to remain in the Order. On death row, Deyell delivers some payback after Miles goes on another racist tirade. Vern finds out he's going to be a grandfather. Said moves in with Adebisi in order to get some proof of Adebisi's rowdy behavior. Simon finds out and delivers a tape of one of Adebisi's "parties" to Said hoping to "gain his trust" as a "brother" Said turns the evidence over to McManus. The result? Querns gets fired, McManus is reinstated and Adebisi and his cronies get moved to Unit B. Enraged about these new developments, Adebisi and Said struggle in the pod and one of them becomes Oz's latest murder victim.

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.

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.

After recovering from his shank wound, Alvarez gains a follower. Busmalis starts a letter writing campaign to get "Miss Sally's Schoolhouse" back on the air. Rebadow finds a way to raise the money for his grandson's treatment. Jia Kenmin returns to Oz after recovering from the coma induced by a blow from Cyril. After Schillinger's released, Redding and Morales form a pact to eliminate the Italians from the drug trade. Schibetta makes a move on the Aryans only it backfires with terrifying results. Kirk continues planning ways to kill Cloutier. After carrying out messages he "received" from Cloutier, Hoyt confesses to all his past murders. Cloutier makes a move that mystifies everyone.

Redding discovers that Busmalis lied about DeSantos. Furious, he confronts Morales and the confrontation gets the two of them thrown in the hole. Cyril gets convicted of the murder and Ryan tells the attorney not to appeal. Meanwhile Sister Pete, Father Meehan and Suzanne Fitzgerald meet to devise another plan in Cyril's defense. Rebadow fumes over not getting the lottery money. Mc Manus' offer to search Oz's databases reveals an inmate with the same blood history as Rebadow's grandson. Rebadow meets the man only to be rejected by him. The rumor of Robson's replacement gums coming from a black patient prompts Schillinger to consult with Aryan Nation leader. The result? Robson gets banned from the Aryans.

At the bi-annual review of solitary prisoners, the board decides to release Alvarez and Schillinger back into gen pop. Rebadow, still mourning the loss of his grandson, gets transferred to work in the library, where he is thrilled to meet the new librarian, Stella Coffo. Meanwhile, Timmy Kirk, now sentenced to Death Row, pleads to Father Mukada to help exorcize him; Ryan O'Reily seeks to prove his brother Cyril had no premeditated plans of murder; and Winthrop makes Schillinger an offer he can't refuse.