As the Nazi invasion of the Soviet Union swept over vast areas of Ukraine and Belorussia from the summer of 1941, over three million Jews were deliberately targeted for annihilation. Shot, hung, butchered, a million and a half Jewish souls were buried in vast pits in Babi Yar, Rumbula, Mariupol, Minsk, Kyiv and Riga. Many accounts began to flood into the Soviet Union where journalist and writer Ilya Ehrenburg began gathering testimonies of the mass murder. This became The Black Book, a chronicle of the Nazi extermination of Soviet Jews. Historian Catherine Merridale travels to Riga, Latvia and Yad Vashem, where the Black Book was smuggled, to uncover this complex story of loss, silence and rediscovery.