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
Set fifteen years in the then-future year 1983, the series tells the tale of the crew and passengers of a sub-orbital transport ship named Spindrift. In the pilot episode, the Spindrift is en route from Los Angeles to London, on an ultra-fast sub-orbital flight. Just beyond Earth's boundary with space, the Spindrift encounters a magnetic space storm, and is dragged through a space warp to a mysterious planet where everything is twelve times larger than on Earth, whose inhabitants the Earthlings nickname "the Giants". The Spindrift crash-lands, and the damage renders it inoperable.
Newspaper reporter Tim O'Hara finds a crashed alien spaceship that contains one live alien. Not wanting to be discovered by the authorities, the Martian assumes the identity of Tim's Uncle Martin and begins to repair his spaceship so that he can return to Mars.
