Oz is in upheaval following the return of Martin Querns; Howell and Robson receive troubling medical news; Alvaraez succumbs to an enticing offer.
Three new inmates arrive at Oz; Busmalis and Rebadow prove to be true Romeos; an awards Banquet ends in a fateful discovery.
Idzik faces his enemies and asks for a transfer; the Muslims run into business trouble; the inmates rally to support the O'Reilys.
Alvarez receives shocking news; Redding's battle continues; Murphy makes a confession to Glynn; Morales' medical suspicions are confirmed.
Glynn receives mixed news on the poison problem; Keller and Beecher work out an agreement; Robson finally gets some redemption.
Schillinger has a disappointing visit with the mayor; Officer Brass spends some quality time with Morales; Cyril O'Reily undergoes an unusual method of therapy.
The unexpected arrival of the mayor spurs an ironic turn involving Schillinger and Beecher; Dr. Nathan discovers why solitary inmates are getting sick.
Alvarez and Schillinger are put back in the general population; the new librarian lifts Rebadow's spirits.
Beecher clears the air about Schillinger; Cyril finds himself in the media spotlight; Morales and Urbano forge an agreement.
Redding and Morales quarrel after Hill recovers; Meehan has an idea to help Cyril; Beecher tries to help Guenzel.
Penders, Hill and Alvarez train Seeing Eye dogs; Nathan and Howell have a heart-to-heart talk; Schillinger's gripe with Said turns deadly.
Redding and Morales forge an uneasy defensive alliance; Keller returns; the Cloutier mystery deepens.
McManus wants Said to help reform White; O'Reilly's mother teaches music at Oz; the FBI stirs up trouble.
Major renovations follow the gas explosion in the kitchen; the prisoners from solitary return.
Hill learns where his allegiance lies; Redding and Morales plan a truce; Beecher worries about parole.
Howell attempts to blackmail O'Reily to get to Cyril; ex-IRA terrorist and Irish refugee Connolly makes a dangerous pact with O'Reily.
McManus starts a series of basketball games, pitting prisoners against one another; a new prisoner has information about Schillinger's son.
Hughes causes trouble in Unit J; Schillinger welcomes his granddaughter into the world; a new inmate threatens Beecher's chance at parole.
Giles stirs controversy; Alvarez despairs of ever leaving solitary; Father Mukada returns to waning influence.
Alvarez offers to be Glynn's informant; Dr. Nathan tests a new drug on the inmates; a love triangle involving Barlog, Beecher and Keller intensifies.
A new inmate arrives ready to take charge of the African-American drug scene; Tidd offers to kill Said; Chinese refugees seek shelter in Em City's common room.
O'Reily (Dean Winters) seeks revenge against a news reporter who did a negative story on him years before.
Glynn withdraws from the race after an attack on Gov. Devlin; Supreme Allah suffers the consequences of making enemies at Oz.
Keller wants to enter rehab to mollify Sister Pete; Beecher plots revenge; Said pledges allegiance to Adebisi.
Mobay pays a price for getting in good with Adebisi; Claire Howell is transferred to Em City to address the increasing lack of diversity.
Querns (Reginald E. Cathey) changes the dynamics of Em City; Mobay (Lance Reddick) takes drastic measures to avoid being exposed.
A new unit manager has unorthodox methods; Beecher worries about his missing children; a new inmate brings trouble.
Glynn discovers the source of Adebisi's gun; Mobay has to choose between taking drugs or blowing his cover.
Glynn fires McManus; Mobay's cover is threatened; Beecher testifies; Alvarez survives a murder attempt.
Warden Glynn attempts to get Emerald City back to its normal routine after two weeks of 24-hour lockdown.
A lockdown ends as New Year's Eve approaches; tensions abound between Ricardo and Alvarez, Howell and Wittlesey, Cyril and his father, and Glynn and McManus.
Sister Pete falls for Keller and reconsiders her vows; McManus is accused of sexual harassment; Adebisi promotes a race war.
Ryan's fixes are nearly uncovered even as Cyril wins another bout; the attempt at peace between Alvarez and Rivera may come undone; Said bunks with Beecher.
Said's leadership is threatened; McManus searches for allies; a crime in the kitchen puts Oz in lockdown.
Schillinger pleads with Glynn for Andrew's safety; Sister Peter Marie institutes a victim interaction program; boxing matches fire up the inmates.
Ryan fixes Cyril's first bout; Schillinger's son is imprisoned; Beecher plots, even as regretful Keller apologizes.
McManus institutes a boxing program; a new inmate confesses a horrifying crime to Hill; Alvarez, confined to solitary, goes insane.
Beecher is released from the hospital; Adebisi is released from the psychiatric ward; Ryan seeks revenge on Schillinger.
Various escape plans are hatched; Schillinger crucifies recidivist Sippel; Alvarez gouges out Rivera's eyes.
Imprisoned Cyril falls under Schillinger's sway; mob leader Nappa wants Adebisi punished for raping Schibetta.
A recovering Schibetta loses control of Oz after being raped by Adebisi; Alvarez is bumped from the Latino power seat; Beecher becomes attracted to his roommate Keller.
Adebisi poisons Schibetta; Gov. Devlin guts the equivalency program; Beecher learns his wife commited suicide.
Augustus Hill's appeal is denied; Richie confesses to the wrong killing; Alvarez is offered conflicting opportunities.
Alvarez knows who raped Glynn's daughter; O'Reily is diagnosed with breast cancer; the Aryans attempt to gain new respect at Oz; a woman arrives on death row.
Emerald City reopens 10 months after the riot; McManus attempts to help inmates receive their high-school equivalency diplomas; Glynn's daughter is raped.
Oz is locked down and Emerald City inmates are put in solitary confinement following the riot; a committee led by a law school dean investigates the riot.
A fight over a checkers game leads to a massive riot in which several officers are taken hostage; the SORT team arrives to battle the inmates.
A recovered Said has the Muslims shun Huseni Mershah; Groves commits murder in honor of Said's power; Beecher gets revenge on Schillinger.
A large number of prisoner complaints keeps the prison health ward in constant demand.
Drugs are smuggled into the prison, and officials are implicated.
Tensions flare when the governor's reinstatement of the death penalty directly affects an Oz prisoner.
Inmates' rowdiness prompts the warden to threaten a lockdown.
The search for a convict's killer begins; the inmates of Emerald City react differently to visits from loved ones.
A correctional facility stresses the rehabilitation of its inmates.