The daily lives of prisoners in Emerald City, an experimental unit of the Oswald Maximum Security Prison where ingroups - Muslims, Latinos, Italians, Aryans - stick close to their mutual friends and terrorizes their mutual enemies.
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.