Historian Niall Ferguson lays out a provocative thesis: the twentieth century's carnage was not two World Wars bookending a Cold War but one extended episode of violence, concentrated in a few unstable borderlands he calls the world's "kill zones," from the Balkans to Manchuria. Ferguson narrates on location, walking sites in Eastern Europe and East Asia where ethnic mixing, economic shocks, and declining empires combined to produce mass killing on a scale no earlier century matched. Archival footage of the trenches, the Holocaust, Stalin's purges, and Japan's war in China is cut against Ferguson's argument that race hatred and imperial collapse, not ideology alone, drove the century's worst atrocities. He challenges easy explanations that blame fascism or communism in isolation, pointing instead to specific geographic and demographic conditions that recur wherever the violence flares. The film builds toward the mid-century decades as the hinge of the whole story, when the century's death toll peaked. It is Ferguson's case for rewriting the standard timeline of modern war.