After Earth is rendered uninhabitable, Androids Mother and Father start a new settlement and family with human embryos on the planet Kepler-22b. Twelve years later, only one child, Campion, remains, and the arrival of an Ark of surviving humans called the Mithraic presents a threat that Mother has no choice but to confront.

Father tries to teach the children how to hunt some of Kepler-22b’s mysterious creatures for food. Meanwhile, the Mithraic make a stunning discovery that potentially fulfills a Mithraic prophecy, and a debate about how to proceed ignites a conflict between Marcus and the Mithraic leader, Ambrose.