The Jupiter 2 is pulled into a giant alien spaceship where there are advanced bubble-like creatures. While John and Don look for maps and equipment Dr Smith and Will look for trouble.

John discovers that the planet they are on will travel further from the sun.In an attempt to survive the Robinsons pack up and head south. Dr Smith stays at the Jupiter 2 site while the Robinson family encounter a terrifying cyclops and an ancient deserted city.

Jimmy Hapgood lands on the planet and the Robinsons befriend him. After helping him fix his spaceship the Robinsons try to convince him to take Will and Penny back to Earth with him. Dr. Smith tries to get aboard the ship instead and take their place.