In the year 1997 the Robinson family take off to colonize Alpha Centauri. A spy from a foreign country AKA Dr. Smith becomes trapped aboard trying to sabotage the project. The ship is whisked off course and into a meteor storm due to Dr. Smith's extra weight upsetting the navigational computers. Smith desperately tries to save himself by reviving the crew. The result: the Robinson family becomes lost in space.

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.

Penny "imagines" a new companion, which is a disembodied life force living below the surface. Dr. Smith accidentally injures Penny, leading to the creature taking his anger out on the entire planet.

The Robinsons can not understand the language of a visiting family also on the planet. The aliens are called Taurons, and come to use the planet as a new colony. However Dr. Smith causes problems between the two camps when he panics and draws a gun on the new family. The Taurons end up not liking the planet and want to be alone, so they leave.

The women of Lost in Space are featured in their very own episode while the boys are out installing communications equipment. Smith is left in charge (boy is that a mistake) and he ""cleans"" their weapons, but cannot remember how to rebuild the weapons. This leaves the J2 crew defenseless.

A creepy creature stalks the Robinson women however they think a small dog is to blame for raids on food and other mischief.

The Keeper, played by Michael Rennie, is a zoo keeper. He wants to take the children and add them to his collection.

This episode is the only two parter from the series.

Dr. Smith holds a seance to contact his Uncle Thaddeus. Instead a spirit creature is contacted and creates havoc for the Robinsons. It is later discovered that the ""spirit creature"" is a physical creature, rendered invisible by the properties of the ""ionized gas"" in the bog from which it came.

An alien boy is sent to Priplanis to validate his prince status. Will is drawn into a battle to the death unbeknowest to his father. Once his real intentions are known John substitutes himself in the challenge and the Alien Ruler substitutes himself for his son.

The Beverly Hillbillies move to Priplanis. One of the aliens turns into a werewolf at night. The leader is a articulent female which Smith tries to court so he may have transportation back to earth. Don falls for the sexy alien daughter.

The Intergalactic Delivery Service comes to Priplanus. Once again Dr. Smith seeks transportation and has Will "test drive" the spaceship. Will returns much smarter than when he left. Smith realizing the same could happen to him, the increase of intellect, boards the spaceship. His trip, however, ends in his rapid aging and subsequent impending death. To make matters worse, the owner of the spaceship has returned to take the vehicle back, stranding Will and Dr. Smith in their altered state.

Dr Smith and Will befriend an old miner named Nerim. After a series of earthquakes indicates that the planet is breaking up, Dr Smith tries to convince them that it is merely the effects of mining, and no harm will come to the planet. John informs him that he is wrong and that the Robinson family will be departing within the day. It is a race against time to escape the crumbling planet.

When an alien believes that the Jupiter 2 has fired a missile at them that alien puts the crew in grave danger for there lives.

Will and Dr Smith discover an old, abandoned Android Machine. When Dr Smith plays with the buttons on the machine, he accidently orders an Android. He thinks he has it for free, and uses her as his personal slave, assuming she has no human emotions. What will he do when the owner, Zumdish, and his guard turn up...demanding payment?

When Dr Smith's cousin Jeremiah Smith arrives on the planet, everyone welcomes him, except Dr Smith. Dr Smith alienates himself from the family, and refuses to return until his cousin leaves. It is later discovered that Jeremiah's reaosns for being on the planet are far deadlier than anyone imagined.

Dr Smith, Will and the Robot discover an old harp under a carved out rock. They discover that in playing the right tune, it unlocks a passage to another world. In travelling here, Dr Smith meets an alien who believes to be the devil, and believes the place to be Hell. When he leaves, and the Alien shows up on the planet, Dr Smith is frightened. Judy befriends the alien, and is accidently taken to the other world. It is up to Don and John to save her, and finally Dr Smith realises it is not hell, and merely a prison world for a criminal.

Athena the girl from the green dimension who hypnotised Dr Smith during thier space flight arrives on the planet. She still is in love with Dr Smith, which he uses to bribe her to help him see the future. However, he promises to go back to the green dimension with him, and when Athena's previous suitor arrives and turns Will green, Dr Smith must find a way to save himself and Will. Urso, Athena's suitor challenges Dr Smith for the lady, customary in the Green Dimension, and after seeing the future, Dr Smith fears the worst. Athena realises he cannot be with her, and leaves with Urso, but not before Urso restores Will's colour.

Dr. Smith's finds an alien ship and wants to use it to get back to earth, but he doesn't count for the owner of the ship admiral zahik to turn up and wreck his plans.

Penny meets up with Verda the Android Dr Smith ordered, who is on the run from a super android, IDAK. She is now much more human-like. IDAK however is faulty and is incapable of crushing anything or anyone. Another OMEGA-IDAK is released, and vows to ""crush, kill, destroy."" Verda hides with the Robinsons but out of fear she and Panny run, when Zumdish and his guard arrive to get her. IDAK is defeated, and Verda and the faulty IDAK take off together, obviously in love.

Will returns to camp following a cosmic storm. John and Maureen are not there as they are at the weather relay station for a few nights. When he gets there, the rest of the family are acting strange. He finds out they are androids, sent to learn how to cope like the Robinsons and teach the rest of their race when they return home. The real Robinsons, are kept in a tube, as they are not allowed to come in to contact with thier double. Will must teach them to become like their counterparts.

After Dr Smith is turned away from camp yet again, he awakes from a nap to find he has been tied up by little mechanical men. The Robinson's camp is invaded the mechanical men of INDUSTRO, who claim that they want a leader..their leader. The Robinson's learn that the Robot is what they want, and that if he is not surrendered the mechanical men will attack. When the Robot surrenders, the mechanical men realise he is not the ""evil"" leader they wanted and they subsequently switch his personality with Dr Smith. An attack occurs when Dr Smith returns to camp wth the voice and personality of the Robot, which Don finds hilarious, and uses to full advantage. An attack ensues and the mechanical men are defeated and turn Dr Smith and the Robot back.

The beginning of the third season finds the Robinsons having to quickly leave the planet they are on, which is a similar plot to the beginning of the second season. Once in space, the robot is swept overboard and has to be rescued. Then the Robinsons find a prison ship filled with cryogenically preserved prisoners. The prisoners have been interred past their normal sentences due to a malfunctioning timepiece on the prison ship. Professor Robinson repairs the timepiece and frees the prisoners. Robby the Robot makes another appearance, threatening Professor Robinson and Major West.

Dr. Smith, Will, and the Robot are accidentally launched in the Space Pod. They land on a planet that is controlled by an alien machine that creates illusions to confuse visitors and drive them away. The Jupiter II lands and rescues them, and the robot destroys the alien machine.

The Robinson's come across a group of space hippies who are trying to destroy the planet the Robinson's currently inhabit. Up up to the Robinson's and Dr. Smith to stop them or they will all be doomed.

The Robinsons encounter two Aliens who are on a mission to seek and destroy an escaped Robot Prisoner, whom they believe to be hiding at the Jupiter Two. Meanwhile, the Robot meets and falls in love with this evil, female Robot. She tries to turn the Robot bad, but ultimately, is defeated by the Robot and the Robinsons, but not before wreaking havoc over the planet.

The Robinsons take in a Princess who is fleeing from a bounty hunter. Will is captured by the bounty hunter, who wants to trade the boy for the princess. the robot then comes up with a idea to save the day.

The Space Pod lands on a planet that is inhabited by creatures who all look alike, and aspire to be different. They capture the Robinsons and make duplicates of them with the objective of using the duplicates to fly the Jupiter II back to Earth. Will is not duplicated, and he thwarts their plan.

A crew led by Captain Kraspo is searching for the missing Princess Alpha. They bring Will aboard their ship who makes them think the Penny might be there princess, because of this the train Penny to be the future ruler of there planet.

Poor Don West is sent to a prison camp.....WITH Dr. Smith!

Don and Dr Smith are installing some equiptment, when Dr Smith comes across and alien prison escapee. The priosoner alien makes Dr Smith change jackets and then runs away. When the prison guards catch up with Dr Smith and Don, they arrest them for aiding an escape of a prisoner.