An alien named ‘Mr Arcon’ shows up suffering ill health. He is being pursued by beings called ‘Saticons’ who are after an amulet he wears on his belt. The Robinsons harbour Mr Arcon in the Jupiter 2. Arcon gives the amulet-belt to Penny and then leaves, so as not to bring more danger to the Robinsons.
Believing Arcon is still inside the Robinsons ship, the Saticons reduce the outside air temperature to below freezing in a bid to force the family to surrender him. Dr Smith travels to the Saticons camp to negotiate a deal with them. After the Saticons show him a key-operated ‘molecular transporter’ machine, Smith agrees to deliver them the amulet in return for transportation back to Earth.
Dr Smith attempts to deceive the Saticons by making a facsimile of the amulet and passing this off as the real one. Likewise the Saticons begin planning a deception of their own. They scan Dr Smith’s memory cells, and based on his recollection of Earth, create an artificial scene of Chinatown. They believe this will fool Smith into thinking he has been transported back to Earth.
When the time comes to test the transportation machine, Smith first decides to send Penny’s pet chimp ‘Debbie’ back to see if it works. When Debbie returns holding a hotdog and an L.A Dodgers baseball pennant, he is convinced the machine has the power to return him to Earth.
Smith and Will return to the recreated Chinatown in San Francisco via the machine, but when they see a fly the size of an albatross they realize they have been tricked and are not really back on Earth. The Saticons realize they have got the dimensions of the fly and other details wrong because they based the Earth copy on Smith’s exaggeration-prone memories.
POSSIBLY THOSE WEIRD SATI’S SHOULD HAVE CHECKED OUT FLY DNA A LITTLE MORE CLOSELY – LIKE MAYBE WITH A CLUNKY 1980’S-ERA ‘BOX’ COMPUTER?
At the same time the Saticons realize they too have been deceived when they uncover the fake amulet. Will, Penny and Dr Smith are preparing to feel their full wrath when Arcon shows up. In a final battle the Saticons are destroyed. Will, Penny and Smith use the transporter to safely return back to the Jupiter 2.