In the year 1997, the Robinson family is cryogenically suspended before their launch into space in the space-saucer Gemini 12 on man's first mission to colonize a planet orbiting Alpha Centauri.
Soon after leaving Earth, a meteor swarm sends the Gemini 12 spiraling out of control, ending in a crash landing on an unknown planet. The Robinsons survive the crash and set up camp, but their preparations to head south to avoid the sudden onset of the cold season are hampered by One-Eye, the giant cyclops, trapping John and Don in a cave.
After Will saves the men, and Penny is recovered after a turtle ride, the travellers journey to the tropics encountering along the way, the One-Eye again, fierce electrical storms, an underground city and a stormy sea crossing where they become caught in a whirlpool.
The Jupiter 2 lands on a planet which apparently serves space as a junkyard. The Robinson's food supply is dwindling, so Dr. Smith tries to sell the robot and the ship in order to get food.moreless
Doctor Smith uses the space pod to land on a planet that the Jupiter 2 is passing by. It turns out that on this planet, plants are the highest form of life and some of them are quite intelligent. One of these plants, a large carrot, captures Smith and tries to change him into a plant.moreless
Dr. Smith disposes of a plant that has grown out of control. However, the plant manages to attach itself to the Jupiter 2, apparently believing that Smith is its mother. Meanwhile, the ship comes under attack by a space warrior.moreless
The galactic showman, Farnum B, returns, this time as the producer of the Miss Galaxy Beauty Pageant. And he wants Judy to be in the contest, only she wants no part of it. Dr. Smith submits her anyway by forging her name to the contest roster.moreless
Don West and Dr. Smith are installing some equipment when Dr. Smith comes across an alien prison escapee. The prisoner alien makes Dr. Smith change jackets and then runs away. When the prison guards catch up with Smith and West, they arrest them for aiding the escape of a prisoner.moreless
Rocketing through space, the Robot suddenly announces that the Jupiter 2 is approaching Alpha Centauri. Everyone is surprised, and the ship lands on a planet, where they are greeted by a group of people who appear to be teenagers from Earth. It turns out that they are aliens who live like Earth-style hippies, and they are incapable of growing old.moreless
Will Robinson meets a man in a cave who may hold the solution to helping them get to Alpha Centauri.
A crew led by Captain Kraspo is searching for the missing Princess Alpha. They bring Will Robinson on board their ship, and he makes them think that Penny might be the Princess they are looking for.moreless
The space pod lands on a planet that is inhabited by creatures who all look alike but aspire to be different. They capture the Robinsons and make duplicates of them with the objective of using the duplicates to fly the Jupiter 2 back to Earth. Only Will is not duplicated and attempts to thwart their plan.moreless
The Robinsons come across a group of space hippies who are trying to destroy the planet the Robinsons currently inhabit. It is up to the Robinsons and Dr. Smith to stop them or they will all be doomed.moreless
Before leaving their planet, the Robinsons meet a boy alien called J-5. They take him with them to return him to his home planet. They meet a strange ship, which turns out to be an Earth "lighthouse" for lost ships. Thinking this ship will help them with extra fuel and star charts they celebrate. However, when J-5 learns that they don't have enough fuel to take him home, he angrily sets about to destroy them all with a creation of his imagination.moreless
Dr. Smith and Penny are entrusted with a valuable amulet after saving an alien's life. However, trouble soon arrives in the form of space thugs, and they want the amulet.