Comets get treated as both origin story and threat in this Spark science documentary, which lays out the dual case scientists make about them. On one side, researchers argue that comets acted as cosmic delivery trucks, seeding early Earth with water and organic molecules that made life possible. On the other, the film walks through the physics of impact: a comet strike can release energy equivalent to a trillion tons of TNT, enough to end civilizations rather than start them. Interviews and animated reconstructions cover known close calls and past impacts, along with the tracking systems astronomers currently use to spot incoming objects long before they arrive. The back half turns to defense, examining proposed methods for altering a comet's course, from kinetic impactors to more speculative nuclear options, and asking how much warning time any of them would actually need to work. It is a survey of where planetary defense science stands now, built on the tension between comets as life-givers and comets as extinction-level threats.