The Uranium Mining and the production of Yellow Cake is the first link in the chain of nuclear development. It has managed again and again to keep itself out of the public eye. The third largest uranium mine in the world was located in the East German provinces of Saxony and Thuringia. Operating until the Reunification, it had the code name WISMUT - German for bismuth, though it supplied the Soviet Union exclusively with Yellow Cake. The film accompanies for several years the biggest clean-up operation in the history of uranium mining.