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 Robinson men discover an underground civilization while exploring the planet. Will wakes a sleeping princess who wants him to remain and rule with her.

John Robinson is possessed by an alien spirit. The alien forces the family to prepare to return to the spirit's home world, even if it requires he sacrifice Will to keep his secret from the rest of the family.

Shortly after leaving their original crash-site planet, Smith spots a familiar star and, in an amazing show of stellar navigational skill, calculates the course to get back to Earth.

He extracts a promise from Don and John that they'll return to Earth, or else he'll destroy his navigation data. They agree, but inform the family at dinnertime that they are headed for Alpha Centauri after all, mainly because the Earth is on the other side of the Sun (how do they know that? - do they know the date? And besides, from Alpha Centauri, Earth revolves clockwise, visible all the time). Smith changes course 180 degrees, then clumsily jettisons most of the fuel.

They reach a refueling barge, one of several that Alpha Control put out in 1996, top up the tanks, and resume course for Alpha Centauri, not knowing that they've picked up a tailgater who follows them after Smith reverses course to Earth again.

The alarm goes off in the night, and they expend a lot of fuel pulling away from the Earth's

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?

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.

During a heat wave, Penny comes across a giant, golden man, and his owner. She is told that the creature is called Raddion, a creation which only needs human emotions to be complete. When Dr Smith is removed from the camp, he is taken by two midgets who work with Raddion, and in another atempt to be returned to Earth, agrees to get the emotions from the Robinsons. He does so by taking their pictures, and all that is needed is for the Robinsons to shake hands with him. Don protests and heads back for camp, as do the Robinsons minus their emotions. Eventually they are returned to normal and it is learnt that human emotions cannot be bought or stolen.

While the rest of the men are away, Dr Smith and the Robinson women are affronted by a mysetrious man in gold, who claims to be at war with a race of green aliens. Penny meets the green alien, and takes a liking to him, and immediately hates the Golden Man. When they are faced with the reality that their planet may be blown up due to war, Penny risks her life to save her green friend, while Dr Smith makes other startling revelations, and renders the family helpless.

Will and Dr Smith are confronted by a knight, who says he is on a quest to seek out and destroy the beast Gundemar. Penny, meanwhile, meets Gundemar and befriends her. Will becomes the pageboy of the knight. When it is discovered that the beast is woman, the knight is unsure whether he can still kill it, leading him to question his life's future.

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.

The crew are outside playing ball when a magician called Zalto. Dr. Smith uses Zalto to conjure up a space ship so he can use it to get back to earth.

Dr. smith hits his head on a rock and goes into the depths of a cave where he finds a mummy, meanwhile the crew have to blast off at 8:00am, and while the also have to rescue Dr. Smith.

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.

With the power source of the Robinson's at a low, they are unable to recharge the Robot. As a result of this the Robot leaves the group, not wanting to be a further burden to them. When they later change thier minds, they cannot find the Robot. Will and Dr Smith discover late one night, but due to the gases in the area he has grown to be bigger than a house. Will decides to only way to reverse the process is for them to go inside him, and work it internally. Will they get out in time?

Dr Smith and Will become trapped in a cave during a cosmic storm. Will is accidently pulled through a cosmic time warp, and ends up on Earth, in Scottish castle. He meets a headless ghost called Hamish who was beheaded at the Castle. Hamish is trapped there due to the callous crimes he has committed. They rest of the family manage to get Will out, but Hamish follows him. They decide to re-create the time warp, and send Hamish home, and with him Dr Smith, carrying star-charts and maps so that he may send a rescue mission to save the Robinsons. Upon re-entering the warp, Dr Smith drops the charts, and Will runs after him to give them to him. They are both taken. When they reach the castle again, Dr Smith and Will realise that they are not in their time. Also, Hamish becomes angry when he realises that Dr Smith is a liar, and has no intention of helping the Robinsons. As an act of reveng he sets out to destroy Dr Smith. In the end, Will and Dr Smith return to the planet, and Ha

Dr. Smith answers a distress call from an alien space ship. He arrives there using the Space Pod, and discovers that the aliens want him to operate on (actually, repair), their leader. It turns out that the aliens are a race of some sort of robot that survive as long as their leader, who functions as their central control timepiece, is in working order. The Robinsons come to Smith's rescue in the Jupiter II. The leader is repaired by the robot, and the extended space family Robinson leave the alien space ship safely.

In an episode reminiscent of the first season episode "The Challenge", Professor Robinson and the Robot land the Space Pod on a planet, and Professor Robinson kills an attacking monster, only to discover that he has interfered with a contest where a highly intelligent alien who aspires to rule his home planet is being judged on how well he hunts. The alien forces Professor Robinson to take the role of one of the hunted animals in the contest, allowing the Professor one weapon. The weapon has a defect that imperils Professor Robinson, but the Professor outwits the alien and survives the ordeal.

Dr. Smith and the Robot are exploring a cave. Smith pushes several buttons on a conspicuous control panel. The buttons activate a cyborg creating device. It up to Will to stop Dr. Smith.

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.

Two aliens, who are actually intergalactic bank robbers, transform themselves into Earthlings. They revive a man named Zumdish who operates a tour agency and they pretend to be his clients. The Robinson's head off and Dr. Smith is left alone, Smith's decides to turn the ship into a hotel and doesn't realize how dangerous his guests are.

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.

Dr. Smith disposes of a plant that has grown out of control, but once outside the plant attaches itself to the Jupiter 2. The plant apparently believe that Dr. Smith is its mother, meanwhile the ship is attached by a brave space warrior.

Doctor Smith uses the Space Pod to land on a planet that the Jupiter II is passing by. It turns out that the planet has evolved in such a way that 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. The Jupiter II lands and the Robinsons and West come to Smith's rescue, only to be captured themselves. Eventually they thwart the plant creature and make their escape.