The human body manufactures its own painkillers to ensure survival when injured. This program shows how opium and its derivatives, heroin and morphine, hijack that natural pain-numbing ability. Illustrating the brain's ability to alter its own chemistry when attacked by drugs, the program depicts the process by which brain receptors become desensitized and thus addicted. Tranquilizers - and the potentially lifelong physical dependency and psychological problems they can cause - are also studied.