One hundred years ago, a mysterious and alarming illness spread across America's South, striking tens of thousands of victims. No one knew what caused it or how to treat it. People were left weak, disfigured, insane, and in some cases, dead. Award winning science and history writer Gail Jarrow tracks this disease, commonly known as pellagra, and highlights how doctors, scientists, and public health officials finally defeated it. Illustrated with 100 archival photographs, includes stories about real life pellagra victims and accounts of scientific investigations.