Under Yellowstone, America's first national park, lies the Yellowstone Caldera, a giant hot spot for volcanic activity. What scientists call a supervolcano. Now after hundreds of thousands of years lying dormant it threatens to erupt. This eruption could wipe out much of the United States killing millions. Suddenly, without warning, a small part of the caldera bursts. Temperatures plummet and the sky fills with dirty, black clouds of volcanic ash and destructive lightning. Lava erupts from the earth, boils over the crater rims, and rushes across the country side at speeds over 100 miles per hour vaporizing forests, animals, and tourists. As the rest of the caldera puffs and steams and threatens to explode, it's up to Yellowstone's top scientist and an adrenaline junkie Park Ranger to halt the erupting caldera. They must plug the lava, as well as stop the poisonous volcano clouds from spreading before the sky turns black and the entire world is frozen in a permanent, apocalyptic volcano winter.