Fighting back tears the U.S. Ambassador to the United Nations, Samantha Power, is standing before the Genocide Memorial in Kigali, Rwanda. It is almost 20 years since up to one million Tutsis and moderate Hutus were slaughtered in the April 1994 genocide. Power has intimate knowledge of the details and chronicled all of it in her Pulitzer Prize winning book, A Problem from Hell: America and the Age of Genocide. Still, on her third visit to the genocide memorials, Power is overwhelmed by what she has just seen.