In 1998, the antiretroviral drug efavirenz was approved for treatment of HIV infection. Though the drug was highly effective, patients soon began to report bizarre dreams, hallucinations, and feelings of unreality. When South African tabloids started to run stories of efavirenz-motivated rapes and robberies, scientists began to seriously study how efavirenz might produce these unexpected hallucinogenic effects. Hamilton Morris travels to South Africa to interview efavirenz users and dealers and study how the life-saving medicine became part of a dangerous cocktail called "nyaope."