The first Western journalists to film in Russia's secret city in the Ural mountains: a walled city which was so secret it had no name and featured on no maps. It also harbored a huge secret: in the 1950's whilst developing Russia's hydrogen bomb an explosion larger than Chernobyl took place and an area the size of the UK was evacuated in 3 days. This exclusion zone has been studied by Russian scientists for decades. The film makers accompany truck drivers to dump radioactive waste in the most radioactive lake in the world, lake Karachai, where the waste from the explosion was buried. The film uncovers what happened during the explosion and what the consequences are for the people and wildlife today.