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 hack ain't comin' back, and everyone's trying to figure out who did the deed; especially Schillinger and Said. McManus hires a new officer Sean Murphy who's also a friend of Tim's. Despite Glynn's reservations, an inmate boxing program is is created and inmates get psyched for the competition. While closely shaving Hill, Coyle gives the gruesome details of his crime, which include the death of an infant and the discovery of indisputable evidence to his claim. Disgusted, Hill decides Coyle should pay and gives the info to Warden Glynn. Adebisi gets approved to work in the AIDS ward. While Howell and Wittelsey converse about McManus, he appears with bad news for Wittelsey. Meanwhile, Schillinger's son Andy has been arrested and is due to arrive to Oz any day. Keller, stir-crazy from being in protective custody, goes back to Em City with painful results. Alvarez begins deteriorating now that his medication has been eliminated.

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.

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.

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.

When Cudney threatens to spill the truth about Cyril's "wins", Ryan solicits Kosygin for help. He then schemes to have Kosygin and Stanislofsky eliminated and finally, tips off the hacks to get Hernandez and Ricardo busted. Busmalis gets a welcome visitor. Sister Pete's questions keep rising after sessions with Keller. Nappa continues working on his new project. Beecher asks Said for lessons in the Islamic faith.

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.

When his plea for an expedited return to solitary goes on deaf ears, Miguel takes matters into his own hands. Glynn finds out who raped his daughter. Hill gets sent to the hole. The boxing finals match ends in tragedy. A hack makes an exit...and an impression .....by leaving a holiday gift for an inmate.

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 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.

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.

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.

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.

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.

Guerra kills Alvarez's new follower and the guilt surrounding it forces Alvarez to make a confession to Mukada. Alvarez, Hill and Penders sign up for a seeing-eye dog-training program. Dr. Nathan attacks a patient while having a flashback of her rape. Cyril shanks and kills Li Chien, which gets Cyril sent to solitary and Ryan sent to the cage. During an interaction session Beecher attacks Schillinger after Schillinger denies ever raping him. Redding asks Glynn for control of the kitchen. Hill's grief over his dead mother and divorce from his wife send him back to drugs happily supplied by Poet. Beecher's new podmate is the son of a prominent family Beecher knew well. Because of that, Beecher decides to protect him from the Aryans at all costs.

Said and Arif go to Warden Glynn about Lalar's murder. Angry and full of rage, Said then confronts White about passing drugs. Unsatisfied with White's response, Said beats White severely, which gets Said thrown in the hole. Chucky Pancamo's condition worsens. On orders from Schillinger, Winthrop gets into a fight with Guenzel. Schillinger goes to with a deal, he'll let Beecher work for him delivering mail to Keller if Beecher has Guenzel transferred to Gen Pop so Schillinger can have him. Keller discovers the feds have compelling evidence linking him to one of the past murders. Meanwhile, Howell makes her move on Keller, Rebadow's ship comes in...for someone else and Hill becomes gravely ill.

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.

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.

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.

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.

The unexpected arrival of Mayor Wilson Loewen at Oz spurs an ironic turn involving Schillinger and Beecher. Meanwhile, Dr. Nathan discovers why solitary inmates are getting sick; a new business plan within Oz inspires Redding; Schibetta looks to puts a curse on the O'Reily family; and some Death Row prisoners get a bang out of a magazine photo shoot.

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.

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.

Everyone has a different opinion of new inmate Idzik; Alvarez receives shocking news; Redding's attempts at reform continue; Murphy makes a confession to Glynn; Morales'(David Zayas) medical suspicions are confirmed; and Beecher's devotion to Keller leads him into a perilous position.

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.

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.

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.