Lost in Space's only Christmas program. Will uses an alien transporter to send himself back to earth. However, many people believe the Robinson family to be dead after hearing the ship went off course. Nobody on Earth believes him, and they lock him up with the intention of sending him to a boys' home.

Will escapes the family home he's in, and wanders around these clueless bunch of townspeople, but finds carbon tetrachoride — needed for the food processors on the Jupiter. Eventually he convinces another boy, Davey, to let him out, and let him return to the planet he came from. He returns to Priplanus with this bottle. Of course no one believes his adventures until he produces the bottle, plainly labeled as coming from Earth.

Penny and Judy stumble upon a mirror. They discover someone is on the otherside. Before they know it they are transported to the mirror universe which is occupied by only one person, a boy who is lonesome for companionship.

After the entire Robinson food supply is wiped out in a freak storm a trader arrives to trade food for equipment the Robinson's possess.

Dr. Smith trades the robot for food and hoards the supplies for himself. Later, after the Robinson's discover his transaction he gets the robot back but in exchange for his own self. The Trader then wants to take Smith as a slave, to another planet.

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.

Due to Smith's actions the crew has had to land there ship on an alien planet which is run by cyborgs. Meanwhile the crew try to break free for the captors who promise them power and luxury and they have to save there robot who was crippled by a ray gun.

The Robinsons and Major West are imprisoned in their camp, after being indited to appear before the a trial in court space crimes. As the trial begins, Dr Smith's name begin's to appear and it is not long before it is realised that all of the Robinson's crimes are due to Dr Smith, and he is indited to appear before the court. Will he be found guilty?

When a troope of Galactic Gladiators arrive on the planet, they challenge Professor Robinson to a duel, which will be aired all of the galaxy. John declines saying he isn't interested in physical combat. Dr Smith takes up the offer when he makes a deal that if he wins, he will be returned to Earth. Unbeknownst to him, if he loses, which is a near-certanty, Earth will be destroyed.

Dr Smith is confronted by an identical look-alike called Zeno, who is on the run from the law. Zeno makes him trade places and Dr Smith, out of fear confesses to Zeno's crimes. He is arrested and he and Will taken away to appear in court. Will the real Zeno be caught before Dr Smith is boiled in oil?

While playing a outdoor match, Will and Smith's ball explodes, and as the smoke clears there ball has turns into gold. the ball rolls into the cave which has 3 aliens inside, the alien wants the robot , which is later stolen when Will refuses to let them have it and Smith does. Can the crew get there robot back.

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.

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.

The primitive beings are actually wards of a computer, Protinius, which can confer temporary advanced sentience on the leading man in order to communicate Protinius' will.

The episode also features a temporary camaraderie between Don and Smith, a burying of the hatchet, when Don is rescued by Smith from a pit, and then says ""Doctor Smith"" - using the word Doctor for the first time unknown ages. However, their camaraderie dissolves and the characters are back to ""normal"". Not the first time Smith has become selfless and a man of some integrity, but as usual, Smith returns to normal.

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.