Iain explores man's relationship with fire. He begins by embarking on an extraordinary encounter with this terrifying force of nature - a walk right through the heart of a raging fire.Fire has long been our main source of energy, and Iain shows how this meant that the planet played a crucial role in Britain's industrial revolution, whilst holding China's development back.Along the way he dives in a mysterious lake in Oregon, climbs a glacier of salt, crawls through an extraordinary cave in Iran and takes a therapeutic bath in crude oil.