The Old Head is the eighth episode in Season 1. The plot features the continuation of the protagonist Michael Scofield's escape plan and reveals the identity of Caroline Reynolds.
Michael finds out a storage room, fundamental to the escape because it is the only building directly over the pipes, has been converted into a break room for the guards, and the team must find a way to set it on fire so that Abruzzi can get them assigned to PI work there. They have to convince Westmoreland, who is a trustee (and thus has access to the break room freely), to help them burn it down.
Michael approaches him with his cat (who ran away during the riots), but he refuses to help. Meanwhile, Bellick starts an investigation into Bob's death, and upon hearing rumors that he died outside of Westmoreland's cell, he goes to question him. Westmoreland doesn't say anything, afraid of being considered a "snitch". Bellick tells him that if he doesn't get an answer before he leaves the cell, their friendship is over. Westmoreland still doesn't cooperate, and Bellick pets Marilyn, saying "...nice cat." A while later, Westmoreland returns to his cell and finds Marilyn dead on his bunk, and spots Bellick looking down on his cell from the second level.
The next day, when Westmoreland goes to deliver the coffee to the break room, he looks at a pack of Bellick's cigarettes and his lighter. Meanwhile, while Michael and Lincoln do PI work, a fire erupts in the break room. Michael approaches Westmoreland and thanks him, but Westmoreland responds with "I didn't do it for you." The group begins by breaking through a drain in the floor and enlarging the hole so that they can fit through it.
Veronica and Nick are nearly killed by an explosion in Veronica's apartment, and go into hiding, because Kellerman and Hale believe they were killed. LJ's mother and step-father are killed by Kellerman and Hale, and they plant evidence in LJ's house that implicate him in the murders. At the end of the episode, the mysterious woman Kellerman and Hale have been talking with throughout the previous episodes is revealed to be the Vice President, Caroline Reynolds, the sister of the man Lincoln was framed for killing.