A Latino Correctional Officer and a former member of the Los Diablo gang, he is an enemy of Latino inmate Raoul "El Cid" Hernandez. After seeing Rivera at work, Hernandez tells disgraced Latino Miguel Alvarez that he can get back into El Norte by blinding Rivera. Alverez attacks Rivera and uses a scalpel to gouge his eyes. Alverez hides out in Father Mukada's office but is quickly caught and is charged with attempted murder and sent to solitary confinement. In Season 3, at the request of Father Ray Mukada, Alvarez is released from solitary on the condition that he attend interaction sessions with Eugene and his wife Tina. These sessions do not go well and Alvarez is sent back to solitary. Later in Season 5, a guide dog program is set up in Oz, Miguel enrolls in it to redeem himself. He asks that Rivera get his dog and Rivera cautiously accepts despite his wife's objections. This is because he wants to make life easier for those who take care of him. Alvarez teaches the dog how to guide and respond in both English and Spanish commands. The Riveras speak Spanish at home and as a result, Miguel does a good thing for a man he wronged.
Eugene starts his job in Oz and works at Emerald City. Shortly after, he sees an old enemy: Raoul Hernandez. Hernandez tells Miguel Alvarez if he gouges out Rivera's eyes, he will let Alvarez back in the game. Alvarez attempts to see his father, Eduardo Alvarez, for advice, but as Eduardo cannot talk after The Haitian cut out his tongue, Alvarez is left without answers. He blinds Rivera with a scalpel and is sent to solitary.
Alvarez is let out of solitary, as Sister Peter Marie Reimondo wanted to interact with Alvarez and Rivera in a controlled setting. Rivera's wife, Tina, doesn't take kindly to the sessions; it's revealed that Eugene wants to kill himself -- he wants Tina to have a life. Alvarez is shown what Rivera's eyes look like and it devastates him.
Alvarez tells Rivera that it wasn't personal, it was to earn his way back into El Norte. Rivera attempts to ask why Alvarez went for him instead of Diane Wittlesey, Karl Metzger, Tim McManus, or Leo Glynn, but Tina interrupted before he got his answer.
As part of a work program, Alvarez trains a dog, which he names Julie, to serve as Rivera's sight companion. Although Tina objects, Rivera recognizes that Julie is Alvarez's way of atoning for his crime and accepts her.