Following a tense effort to rescue John Robinson from deep space, the Jupiter 2 is drawn inside a massive alien spaceship. There, the family confronts a strange race of bubble creatures.
The Jupiter 2 lands on a planet Dr. Smith mistakenly believes is Earth. When Smith is lured out of the ship by cyborgs masquerading as earthlings, the Robot saves him - and the family - in the nick of time.
When Dr. Smith and Will discover a magic wish-granting machine, the family becomes intoxicated with greed. But the party ends when a strange alien creature reclaims the magic machine.
A strange galaxy tribunal imprisons the family, and attempts to try the crew members for crimes committed in outer space. The Robinsons are vindicated, while Smith is excused by reason of insanity.
A friendly little dog survives the crash of a space capsule and leads Professor Robinson and Don West to Judy, just in time to save her from the claws of a giant hairy mutant.
