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.

After a confrontation with Marcus, Mother discovers and takes five Mithraic children (Hunter, Tempest, Paul, Holly and Vita) back to her settlement. While Mother, Father and Campion, adjust to living with a new group of Earth-born children, Marcus struggles to survive alone on Kepler-22b.

After the Mithraic kids fall sick, Campion believes Mother is poisoning them and plans an escape. As Mother and Father attempt to prove otherwise, Marcus and Sue work to convince the other surviving Mithraic to mount a rescue of the children, desperate to get their son Paul back.

As Marcus continues to embrace his Mithraic devotion, Sue worries he may no longer have her and Paul’s best interests at heart. Meanwhile, Mother experiences what she believes to be malfunctions, and Hunter works on a secret project with Father.

Sue is determined to keep the children safe, and in doing so, struggles with whether or not she can trust Mother. Meanwhile, a new threat arises and an increasingly erratic Marcus causes the Mithraic to question their leader.

Paul begins displaying troubling behavior not unlike that of Marcus, leading to a shocking discovery. Father struggles with human-like emotions. Mother and Father discover a startling secret about the planet they’re on, just as a new threat arrives on Kepler-22b.