Nazi Germany's economic planners had a problem: no reliable source of fat and oil for a country preparing for war. Their solution was whale blubber, and between 1936 and 1939 the regime built the third largest whaling fleet on Earth, seven purchased factory ships and more than fifty catcher boats fitted with modern harpoons, to close what officials called the "fat gap." This film traces that industrial effort into the Southern Ocean, where at least 15,000 blue and fin whales were killed in three seasons, and uses interviews with some of the last surviving eyewitnesses to reconstruct life aboard the factory ships and the scale of the slaughter. Archival footage of the hunts and the rendering operations sits alongside expert commentary on how the whale populations targeted have still not recovered, decades later. The film's real subject is the collision of natural history and war economy: how a resource extracted from the sea became fuel for margarine, explosives, and ultimately German rearmament.