In this perfect match of author and subject, Pulitzer Prize–winner Samantha Power tackles the life of Sergio Vieira de Mello, whose work for the U.N. before his 2003 death in Iraq was emblematic of moral struggle on the global stage. Power has drawn on a staggering breadth of research (including 400 interviews) to show us a heroic figure and the conflicts he waded into, from Cambodia’s Khmer Rouge to the slaughter in Bosnia to the war-torn Middle East. The result is a peerless portrait of humanity and pragmatism, as well as a history of our convulsive age.