It is 120K years AD. Humanity has suffered 53 nuclear holocausts (this was made possible by advanced recovery methods researched over time). Peace for 18000 years is being upheld by an artificial intelligence which governs a flying city, eradicating advanced human settlements which threaten to develop into nuclear threats. A group of cavern dwelling humans aim to destroy this flying city by detonating a hydrogen bomb at the right place at the right time.