On April 2, 1979, a mysterious powder wafted unseen into the air from a chimney that rose 25 meters above a Soviet military camp some 1,400 kilometers east of Moscow. Over the course of the next few weeks, at least 80 residents in the surrounding Central Asian city of Sverdlovsk, now known as Yekaterinburg, fell ill with what at first seemed like flu. After a few days, however, they developed massive internal bleeding, among other problems, and 68 or more of them died.