Yellowstone National Park sits on top of one of the largest volcanic systems on Earth, and this BBC two-part film imagines what happens when it finally erupts. The first part is a dramatized disaster scenario, following scientists, park rangers, and a family caught inside the caldera as tremors build toward a full eruption, complete with ashfall reaching across the United States and a mile-high plume disrupting the atmosphere. The second part steps back into documentary mode, with volcanologists and geologists explaining the real science behind the dramatization: the caldera's history of eruptions roughly every 600,000 years, the monitoring equipment tracking ground deformation and gas emissions, and the evidence used to model an event nobody has ever recorded firsthand. The blend of reenactment and expert interview lets the film make a specific, testable claim, that a Yellowstone supereruption would be a continent-altering event, then show the actual data supporting or complicating that claim.