After a series of portentous dreams, Richard Moss is drawn to a secluded spot in Ashdown Forest. He witnesses a spacecraft landing and is taken to a distant planet called Terra Nova where inhabitants of Earth migrated 5,125 years ago. Terra Nova is ruled by a 'Great Leader' named Ezra who oppresses his people. Richard is imprisoned but then rescued by a cosmonaut named Noah and he joins the resistance, forcing Ezra out of power.

Richard learns he was brought to Terra Nova to equip him to return to Earth to help avert a similar disaster recurring there. He hears a Mayan prediction of an impending cataclysmic event as another cosmic cycle of 5,125 years is about to end. A deadly asteroid is heading for Earth which will lead to the extinction of its inhabitants unless a way can be devised to divert it.