Who killed five American nuns in 1992, and why has no one been held responsible? FRONTLINE and ProPublica investigate a mystery from the midst of Liberia’s bloody civil war, in which hundreds of thousands of Liberians died. The five sisters were on the front lines, tending to the sick and distributing medical supplies. “There are no problems in this world,” one of them liked to say. “Only challenges.” (Source: Frontline)
