Under the bubbling hot springs and geysers of Yellowstone National Park is a supervolcano. Most people don't know it's there. The caldera is so large that it can only be seen from a plane or satellite. It just could be overdue for an eruption, which would change the landscape and climate of our planet.

For Alex, being left alone for the weekend means having the freedom to play computer games and hang out with his friends without hassle from his mother. Then the Yellowstone supervolcano erupts, plunging his hometown into a nightmare of darkness, ash, and violence. Alex begins a harrowing...