In 1899, an eccentric inventor perfects an anti-gravity substance and builds a makeshift spacecraft, taking his neighbor and the neighbor's fiancée along on a journey to the Moon. There they find an underground civilization of insect-like Selenites and narrowly escape back to Earth, unknowingly leaving behind a contagion that a UN expedition decades later finds has wiped out the lunar city entirely. Adapted from H.G. Wells's novel, with stop-motion effects by Ray Harryhausen.