Beneath Yellowstone National Park a super-volcano has started rumbling. It's been there for a very long time, though most Americans are not aware of it. Every three hundred thousand years or so it erupts with devastating consequences. Scientists say it's getting ready to erupt. Naysayers say it's a hoax. The Interior Department closes the park and orders an evacuation. Most people comply, and those who don't stay behind knowing they're risking a very violent death. Millions will die. And the lives of every survivor will be changed forever. There really is a super-volcano beneath Yellowstone National Park. It really has erupted in the past and WILL erupt again. And when it does scientists say it'll take up to twenty percent of the United States with it. You do not want to be in that twenty percent.