simon schama on his friend. >> he was an irreplaceable union of head and heart. he had a mind like a razor blade. >> hello. statistics about karachi are quite disturbing. it is one of the most densely populated areas in the planet. an estimated 21 million people call it home. there are even more startling facts about karachi. heroine is cheaper than food. it is a city of addicts. we have this report. >> in this sprawling port city, there is an estimated half a million heroin addicts. that is one in 40. this state has very little public health provisions, so it is up to charities to close the gap. this foundation it was once thought to be the world's largest drug rehabilitation center. without the resources to offer conventional treatment like methadone, 4000 patients are given only paris see small -- paracetemol to help with the pain. every day, the foundation is called by the families of the addicts so desperate for help they are willing to have their loved ones locked up. >> what are you doing? >> [speaking foreign language] [siren] >> [unintelligible] >> they