On 27 August 1883, the volcanic island of Krakatoa in Indonesia's Sunda Strait tears itself apart in a series of eruptions loud enough to be heard thousands of miles away. This film reconstructs the event hour by hour, using dramatized scenes alongside expert testimony to show what happened to the people living on the surrounding coasts of Java and Sumatra: tsunamis wiping out entire villages, a rain of pumice and ash blotting out the sun, and a pyroclastic surge of superheated steam, sulfuric acid, and ash rolling across the strait fast enough to kill from a distance. More than 36,000 people die, many of them not from the blast itself but from the burns and drowning that follow in its wake. Volcanologists and geologists explain the mechanics behind the collapse, how a chamber of magma emptied itself so violently that the island's core caved into the sea, triggering the waves that did most of the killing. The film treats Krakatoa as both a human catastrophe and a case study in how little warning a volcano can give before it ends a region.