When a widower with ten children marries a widow with eight, can the twenty of them ever come together as one big happy family?

The space family Robinson is sent on a five-year mission to find a new planet to colonise. The voyage is sabotaged time and again by an inept stowaway, Dr. Zachary Smith. The family's spaceship, Jupiter II, also carries a friendly robot who endures an endless stream of abuse from Dr. Smith, but is a trusted companion of young Will Robinson