More than 90 percent of all species that have ever lived on Earth are extinct, and the film opens with that number before asking why extinction happens in sudden pulses rather than a steady drip. Across the last 500 million years, at least a handful of events have wiped out 50 to more than 90 percent of species on the planet within a geological instant, and the film lays out the physical evidence for what causes them. Volcanic eruptions and asteroid or comet impacts are treated as the leading suspects, each capable of throwing enough debris into the atmosphere to block sunlight for months, killing plants first and then the animals that depend on them. The film also covers the second wave of damage: toxic gases and heat-trapping emissions released by the same events, which can trigger runaway warming once the dust clears. The causes remain contested rather than settled, and the film presents them as live scientific arguments rather than a solved case, using the geological record itself as the evidence on screen.