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?

A person know as ' the thief from outer space' appears in a puff of smoke, will agrees help help him rescue a princess who was lost more than 200 years ago by evil vizier.

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 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.

Dr Smith discovers another Android Machine, in the middle of a dangerous fisher. When he tries to order something, he is trapped inside the machine. Later when Will tries to get him out, he too is sucked in. Zumdish arrives on the planet in order to destroy the faulty, forgotten machine. Meanwhile Will and Dr Smith discover the magical Toymaker's world, as they are mistekn for toys. They later discover they are close to earth. Will they return to Earth, be blown up, or Will Professor Robinson and the Robot be able to save them.

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.

Alonzo P. Tucker returns, this time more in keeping with the pirate character he tried to create in his first appearance. This time Tucker is searching for Billy Bones' treasure, and is using the head of Billy Bones, which is kept in a box, to help him find it. He has three cutthroats with him, and he has to find the treasure and keep the cutthroats from endangering the Robinsons. Tucker's robotic bird is back again, and continues to torment the robot.

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?

As they are rehearsing a play, Dr Smith, Will, Penny and the Robot encounter a creature who appears to be suffocating. Dr Smith refuses to help out of fear but Penny helps him. The alien puts himself in human form so that he may breathe the atmosphere. He says he is Mr Arcon. Penny takes him back to the Jupiter II to rest. Later he gives Penny a gift which he says she must guard with her life. He tells her that as long as she wears the belt, she will be safe. He disappears, and it is not long before a group of aliens turn up, looking for the belt. They inflict immense cold on the planet as a way of trying to get the belt, but Penny refuses despite pleas from Dr Smith. Dr Smith makes a copy of the Belt and tries to give the fake to Aliens. They are angry, but still want his help. They promise to return him to Earth should he get the belt. Dr Smith and Penny go through the Alien's machine, where they have created a world from the Dr Smith's memory, which will trick them in to

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.

Will is conducting an experiment in a cave and captures a man who claims to be the man who controls time for the entire universe. This ""Time Merchant"" takes Will, Professor Robinson, Smith, and the Robot, to his secret lair. From there, Smith uses the Time Merchant's time machine to return himself to Earth on the day the Robinson's departed, with the objective of NOT sabotaging the Jupiter II mission and letting the Robinsons go on their way to Alpha Centauri. The Time Merchant then announces that if Smith does not get on the Jupiter II, the ship will not fly off course and will therefore be destroyed by a collision with an asteroid several months after liftoff. So Will is sent back to join Smith and try to convince him to get on the Jupiter II as he originally did.

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.

The Jupiter 2 lands on a planet which serves 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. Can Dr.Smith be stopped?