The Mexican Mafia began as a prison gang in California's penal system and grew into one of the most entrenched criminal organizations in the United States, controlling drug trafficking and extortion rackets that reach far beyond prison walls into the streets. This episode of the Gangland series traces that path from cellblock to street corner, using interviews with former gang members and law enforcement officials alongside archival footage and reenactments to lay out how the organization is structured and who runs it. It follows both the leaders who give orders from inside prison and the members who carry them out outside, and it covers the police and prosecutors trying to dismantle a network built to survive incarceration. The picture that emerges is of a gang whose power comes precisely from the fact that locking its members up does not stop it from operating.