Lightning kills more Americans in an average year than tornadoes, and this film sets out to explain why something so common remains so poorly understood. Meteorologists and storm researchers walk through how a bolt forms, why it is nearly impossible to predict exactly where it will strike, and what happens to a body or a building when it does. Survivors describe being hit and living with the aftermath for years, while scientists explain the tracking networks and warning systems now used to give people a few extra seconds to get indoors. The film also makes the counterintuitive case that lightning is not simply a hazard to be eliminated: it plays a role in the nitrogen cycle that sustains plant life, meaning a world with none of it would be worse off, not safer. The recurring advice, delivered plainly rather than dramatically, is the same one meteorologists have pushed for decades: when thunder roars, go indoors. Part of the Fatal Forecast series on natural disasters.