Seven scenarios for human extinction, ranked in countdown order by ABC's 20/20 team and narrated by Keith David. The list starts with gamma-ray bursts and black holes born from dying stars, then moves to artificial intelligence and the risk of machines turning against their creators. A supervolcano eruption at Yellowstone takes the fifth spot, discussed through the geology of the caldera sitting beneath the park. Asteroid impact, nuclear war, and pandemic disease follow, each weighed by scientists for how plausible and how survivable it would actually be. The program saves its final and, by its own argument, most urgent threat for last: climate change already underway, illustrated with interviews on rising sea levels, more frequent natural disasters, and ecosystems under stress. The structure is a straight countdown from the most remote danger to the one already in progress, and the film's case rests on that ordering, treating cosmic catastrophe as a thought experiment and climate change as the threat already inside the house.