Friction is growing in the wake of two deaths so Said, Wiseguy leader Schibetta and Gangbanger Jefferson Keane are brought together by Warden Glynn, who tells them to keep their boys quiet or else he'll lock the prison down.

Governor Devlin has reinstated capital punishment in the state--and the first Oz prisoner scheduled to die is Jefferson Keane, who killed a Latino in their skirmish. Before he's executed, Keane donates a kidney to his ailing sister.

The infiltration of drugs into Oz has reached scary levels, and the efforts of McManus and Glynn to find out who's smuggling backfire in a deadly way. Despite a lockdown, drugs continue to trickle in--and the blame shifts to corrupt officials.

Ricardo is discovered to suffer from Alzheimer's; Beecher flips out and sends Schillinger to the hospital; mob boss Schibetta develops stomach problems thanks to some ground glass; and Said has a heart attack.

A recovered Said ostracizes Huseni Mershah for turning his back on him when he was dying--and orders all the Muslims to cast him out. Impressed by Said's power, Groves decides to kill Glynn in his honor, but ends up stabbing an officer by mistake.

After a visit with his sons, Schillinger realizes he needs to get paroled. He convinces McManus to let him return to Em City with the condition that he leaves Beecher alone. Beecher comes out of the hole hell-bent on making sure Schillinger doesn't get paroled. McManus gets wind of Wittlesey and Ross' contraband operation and orders her to shut it down. Ross makes it very clear to her that this will not happen. The Muslims meet and discuss how the riot will begin. However, two rednecks beat them to it by fighting over a game of checkers. This causes all the inmates to get involved and they quickly overpower the COs who are trying to break it up. Said orders the Muslims to get out and seize control. Said pulls out the gun he acquired from a rookie CO and fires a shot into the air, causing Em City to quiet down. Said meets with Ross, Adebisi, O'Reily and Alvarez to discuss strategy and demands. Said agrees to let O'Reily, Ross and Adebisi control the main gate and Alvarez will control the hostages. Dobbins was seriously injured during the initial uprising and Hill convinces Vayhue to step up and help. Vayhue and Dobbins leave Em City only to be beaten up by SORT. The hostages require medical attention, so Alvarez and Said vote in favor of a doctor. However, Adedisi, Ross and O'Reily vote no. Governor Devlin orders the National Guard to surround the prison and take it back, but Glynn and McManus think they should see the demands first. McManus volunteers, to Devlin's disgust, to enter Em City to deliver food and check on the hostages. He tries to get COs Armstrong, Mineo and Wittlesey free in exchange for himself. He gets Armstrong and Mineo released, due to their injuries but Wittlesey has to stay. After reading the demands, Glynn realizes that the prisoners are being quite reasonable, however Devlin orders the National Guard and SORT to re-take Em City anyway. Meanwhile Ross' men and Adebisi's are constantly fighting, so Said tells O'Reily to switch Ross' men with Alvarez's at the front gate. A short tie later, Adebisi's men start to fiend due to the depletion of heroin, resulting in a major skirmish. Just as that situation is resolved and the Homeboys are tied up, the lights go out. Said realizes the situation and orders Ross to bring out the hostages as a front line of defense. Soon tear gas is thrown into Em City, then a tractor breaks through the barricade and gunfire rings out in Em City.

Season Two premiere. In the aftermath of the riot that killed six inmates and two officers, Oz is locked down, and Emerald City prisoners are sent either to solitary or gen pop. A special committee is appointed to investigate the riot.

Ten months after the riot, Em City is reopened. A recovered McManus creates a council of group representatives to keep order, and initiates classes to help inmates get high-school equivalency diplomas.

Alvarez knows who raped Glynn's daughter, but refuses to tell the warden. Wangler is making progress at school, but his cellmate, Adebisi, isn't a fan of higher education. When Hill's judge is convicted of accepting bribes, Said takes up Hill's case.

Augustus Hill's appeal is denied, despite the efforts of Said, who has better luck with Poet's poems. Meanwhile, O'Reily survives his lumpectomy, and now focuses his attention on Dr. Nathan.

With their enmity at a boiling point, Adebisi poisons Schibetta--but not fatally. Now that his brother has turned himself in for murder, Glynn no longer owes Schibetta any favors.

Schillinger attempts to enlist Said to get him out of jail. Recovered from being poisoned, Schibetta is brutalized by Adebisi, losing 'control' of Oz. Meanwhile, Alvarez is bumped out of the Latino power seat by Raoul Hernandez, a.k.a. El Cid.

Cyril O'Reily, Ryan's brother, is imprisoned and falls under Schillinger's control. Ryan tries to get him away into Em City, but Cyril winds up in the hole. El Cid tells Alvarez there's only way he can 'stay in the game.'

In the Season Two finale, Wittlesey is transferred to general population and replaced by Karl Metzger, a Nazi. Mack and another Aryan try to escape through Busmalis and Rebadow's hole. Hill gets the idea of escaping Oz by hiding in a coffin.

In the Season Three premiere, Beecher is still in the hospital after Schillinger and Keller broke his bones, Alvarez is still in solitary for blinding Rivera, Adebisi is back in the kitchen and McManus starts dating a newly arrived CO.

No one knows who killed Metzger. Meanwhile, McManus hires his friend Sean Murphy as a C.O. and he launches a boxing program. Hill faces a dilemma when a new inmate reveals a terrible crime. Adebisi sticks Nappa with an AIDS-infested hypodermic.

In the boxing program, O'Reily spikes Robson's spritzer bottle before his bout with Cyril. Rebadow's mother tries to persuade him to meet his son and grandson. Meanwhile, Nappa finds out he's HIV-positive and is moved to Cell Block E.

O'Reily and Keller plot to take care of Andrew. McManus is forced by prison brass to settle Howell's sexual-harassment suit. Hanlon's murder convictions get overturned and he's allowed back in the general population--where he finds new troubles.

Wangler 'finds out' his wife and her lover were murdered execution-style. Meanwhile, Poet and Pierce get burned by Hernandez, Ricardo and Guerra. Lockdown ensues, and Wangler finds himself vulnerable--and in a cell with Adebisi.

With Cyril scheduled to box Pancamo, O'Reily plans to use his spray-bottle trick, but first he must deal with Cudney. Alvarez sees the photos of Rivera's gouged-out eyes and goes nuts. New roommate Nat Ginzburg offers to be Nappa's secretary.

Adebisi accuses McManus of sexually harassing Wangler. Bellinger meets with McManus and requests execution by hanging. Just one problem: she's pregnant.

Brace yourself for the explosive Season Three finale! As the new millennium approaches, things are heating up in Em City as racial tensions mount. Glynn fires Hughes, but before leaving, Hughes delivers a millennium gift to Adebisi: a gun.

Season Four premiere. The world of Oz--an experimental prison within a prison known as the Emerald City--reopens its doors with the inmates still on a 24-hour lockdown and prison officials struggling to end the hostilities.