In São Paulo's House of Detention, prisoners welcome the Doctor, who has recently arrived, eager to begin an AIDS-prevention program. The Doctor is faced with extremely serious problems inside Latin America's largest jail: overcrowded cells, decaying facilities, diseases such as TB and the beginnings of an AIDS epidemic. The inmates have access to neither medical care nor legal assistance. Carandiru, housing 7,000 prisoners in a facility meant for 3,000, is a huge challenge for the newcomer.

But after working there for a few months he perceives something that will transform him: the inmates, even in this appalling situation, are not demonic figures. In his daily contacts with the prisoners, the Doctor witnesses solidarity, organization, and above all, a great will to live. The Doctor earns the respect of the inmates and with respect comes secrets. The inmates start to tell him their life stories. His meetings with patients in the ward become "windows" into the world of crime. But the overcrowding and primitive conditions eventually lead to tragedy.