Because of the issues surrounding the death of Scott Ross, Tim McManus transfers Diane Wittlesey out of Emerald City to Unit B. McManus selects as her replacement Karl Metzger, familiar to some inmates from his prior assignment in "Ad Seg" (Administrative Segregation), to become the new "Head C.O." of Emerald City. Metzger then makes life easy for the Aryans, who begin a violent rampage against other inmates. Metzger assists Schillinger and the Aryans with the crucifixion of Robert Sippel, a paroled former priest and child molester imprisoned in Oz.
Inmates Mark Mack and another Aryan discover Agamemnon Busmalis and Bob Rebadow's tunnel. They inform Rebadow and Busmalis they will turn them in unless they switch pods so Mack and his Aryan brother may escape. Mack then asks Metzger to change cells with Busmalis and Rebadow. Metzger asks McManus for permission, who tells Metzger that he trusts him to make the decisions. Metzger swaps out Mack and the Aryan with Busmalis and Rebadow. Busmalis comments to Rebadow that he had weakened the supports in the tunnel. During the night, while Mack and the Aryan are attempting their escape, the tunnel collapses, killing both. Metzger also assists Vern Schillinger in his war against Tobias Beecher. Metzger takes Tobias Beecher to the gym, where Schillinger and Chris Keller break his legs and arms.
After Mack and the other Aryan's death, Metzger takes eventual revenge on Busmalis. While cleaning a cell window, Busmalis is choked by Metzger and thrown down the stairs, ending up in the hospital. Rebadow tells McManus Metzger is favoring the Aryans. McManus researches Metzger's past and discovers that he was a member of a white supremacist group (perhaps not coincidentally, he shares his surname with, Tom Metzger, the leader of White Aryan Resistance, one of the most prominent white supremacists in America). Metzger also has a tattoo common with the Aryans in the prison. He asks Leo Glynn to fire him, but Glynn refuses to do so without solid evidence against Metzger. McManus asks Beecher and Busmalis to testify against Metzger, but both refuse.
Beecher meanwhile is released to Oz from the hospital and is looking for vengeance. Beecher is seen constantly sharpening his nails, which he had not cut since being assaulted. Chris Keller begs Beecher for forgiveness, to which Beecher says he must tell McManus that he, Schillinger, and Metzger were involved in his assault. Keller emerges from their cell and demands to see McManus, making Metzger suspicious. Metzger takes Beecher to a dark place in the prison, asking what Keller is planning to tell McManus. There, Beecher suddenly attacks, slices Metzger's face and throat using his nails as razor sharp knives. Metzger tries to call help, but dies before he can speak in the radio. Beecher then returns to his cell, cuts off his nails, and flushes them down the toilet.