The narrator recounts an accidental partnership with an eccentric inventor who develops cavorite, a substance that neutralizes gravity, enabling them to build a spherical craft and travel to the Moon. On the lunar surface they explore landscapes, observe unfamiliar ecosystems and an organized insectile civilization, attempt communication and face conflicts that separate the companions. The account blends personal adventure, scientific speculation, dispatches sent back to Earth, and detailed natural history of lunar life, concluding with the surviving narrator returning to relate the observations and messages received from his absent companion.