In 2099, Earth shifts off its axis and begins rotating at an angle of 90 % relative to the 20th‑century equator. Three years of natural disasters follow. When the crisis subsides, the planet’s ten‑billion population has perished, leaving only two million colonists on the Moon. Some of those on Earth return to repopulate the world by establishing seven new cities, while the Moon’s remaining colonists fear that their former neighbors could pose a threat. In response, they build a ring of defensive satellites to trap any returnees on the newly repopulated homeworld.