The Carandiru House of Detention, in the teeming city of São Paulo, was the largest and most crowded prison in Latin America. Known as the 'Old House', it was also highly unusual in the way it was governed. Closed to the outside world, and even largely to the wardens, it was run almost entirely by the inmates themselves, who created a unique society complete with politics, hierarchies and a system of justice.

In 1989, at the height of the AIDS epidemic in Brazil, with only a handful of physicians attempting to treat an inmate population of over 7,000, the medical situation at Carandiru was dire. A city doctor, Drauzio Varella, volunteered his time at Carandiru over the course of thirteen years, in an effort to combat the rampant disease. As he gained the inmates' trust he was given access to their society, where he was overwhelmed by the profound humanity and freedom of spirit shown by these men, despite their terrible crimes and the inhuman conditions in which they lived. Lockdown is Varella's powerful depiction of life on the inside, wherein he recounts the prisoners' colourful and surprising stories. The book ends with the massacre by the police of the prisoners that ultimately brought down the 'Old House'.