Samantha Power found her voice as a journalist in the darkest corners of the world, reporting from the front lines of civil wars in Eastern Europe and Africa. As her new book on the late Brazilian diplomat Sergio Vieira de Mello hits shelves this month, some influential people are paying attention to that voice—including Barack Obama, whom Power advises. In Chasing the Flame: Sergio Vieira de Mello and the Fight to Save the World,Power explores the legacy of Vieira de Mello, who was killed in a 2003 truck bombing in Iraq. His death, Power writes, was a blow to early humanitarian efforts in Iraq from which the United Nations and the United States are still recovering. Iraq, meanwhile, is still waiting for a rescue. Power discusses and signs copies of her work at 7 p.m. Tuesday, Feb. 19, at Politics and Prose, 5015 Connecticut Ave. NW. Free. (202) 364-1919.