The orbit of the Robinson’s planet has become erratic and dangerous. Since the planet will soon collide with a comet, the Jupiter 2 makes an emergency lift-off and departs. They manage to escape the gravitational pull of the comet and continue safely through space.
Doctor Smith records an SOS message to toss out of the ship, but when he opens the hatch, the Robot gets sucked through and out into space. No one wants the Robot to drift through space alone forever, so John puts on a spacesuit and goes out to rescue him. He doesn’t manage to do so,and the Robinsons are drawn through a supernova but luckily, the Robot manages to get back on his own.
The Jupiter 2 is pulled into a void, where they dock at a strange ship. John and Don decide to get out and look around for spare parts. They find many people aboard, all frozen. It appears to be an automated prison ship that has somehow fallen into disrepair. Its only crew is a computer and a robot guard. John discovers that the time lapse computer which was supposed to measure the sentences of the prisoners has also been frozen and stopped working long ago.
Smith, Will and the Robot later go down to investigate as well. Doctor Smith decides to thaw one of the prisoners out and is immediately attacked by the man. The prisoner, whose name is Phanzig, forces Smith to stand on a freezing pedestal and commands him to stay there. Smith disobeys and runs off, and an alarm sounds.
The robot guard hears the alarm and sets off to find the escaped prisoner. He ends up finding Don instead, and he freezes the Major and takes him away for questioning. Phanzig catches Smith once again and forces him back onto the freezing pedestal. Smith tells Phanzig that they can both escape because he has a ship, and Phanzig decides that they can work together.
Will and the Robot find John, and they all set out to look for Don and Doctor Smith. Poor Don is tied up, being questioned by the robot guard and the computer. Phanzig discovers the time lapse clocks have all been frozen and he orders Smith to help him free the other prisoners. Once free, the prisoners riot, forming a mob and rushing to the central control room.
When they arrive, they find Will, Don and John in the control room already. Phanzig says they are taking over the ship, and plan on destroying the computer and its time lapse clock. John talks some sense into them, managing to convince the prisoners to let him repair the clock instead. Once the clock is fixed, the computer announces that the prisoners are all free and will be taken back to their home planet. Phanzig and the prisoners are all very happy, and the Robinsons collect the spare parts they need and go back to the Jupiter 2.
- This is the first episode of the the third and final season.
- The Robinsons have been trying to lift off for a huge amount of time, and yet somehow do it here at the slightest notice.
- Comets are not hot. This misunderstanding of the laws of physics also complicated The Derelict. Comets are also relatively light compared to planets. Halley's Comet is only one ten-billionth the mass of the Earth. If the Jupiter 2 can lift off and get away from the planet it should have not a problem evading the gravity pull of a comet.
- This is the first episode of the third season, and there were numerous changes between this and the previous seasons. Everyone has new costumes, with the men's outfits having a more unifying theme. The opening credits were redesigned to reflect the intent of establishing an action/adventure tone. To begin with, the teaser would end on a freeze frame, then the screen would be filled with a countdown from 7 to 1, which would then lead into a new opening credit sequence and theme. This was meant to prepare the audience for a more action/adventure based series.
- This is the first appearance of the lighter, stunt Robot used for more complicated scenes. It should be noted that this second Robot was referred to as the Dummy Robot on all original series paperwork.
- In the first scene, the sand is missing from the floor of the set. This was removed to facilitate the filming of the spacewalk scene.
- Marcel Hillaire would coincidentally return in the final episode of the season (and series), Junkyard In Space.
- Several of the frozen prisoners are seen moving on their freezing pedestals.
- The prison ship "Verah Castle" is a modified re-use of the alien spacecraft model from the first season episode The Derelict.
- Since a comet is heading for the Robinson’s planet, it will most likely be destroyed. In order to save themselves, the Robinsons blast off in the Jupiter 2 and head elsewhere. What happened to the other citizens of that planet, such as Tiabo whom we met in the episode “Forbidden World”? Did the Robinsons give them warning to evacuate as well, or were they just left behind to die?
- One only needs to glance at the frozen prisoners to know they are dangerous men. Is Doctor Smith really stupid enough to unthaw a murderer just to play a string game with him? Apparently he is!
- Why were the prisoners allowed to keep their weapons?
- When Will, Smith and Robot leave the Jupiter 2 to explore the prison ship, how did the Robot climb down that tiny ladder?
- The spare parts Don and John find on the prison ship are obviously alien technology. How can they be so sure alien parts will work in an earth-made ship?
- Phanzig gives Will his strangling-rope as a gift, and Will is thrilled!
- When Will and Dr. Smith look in the first window,the prisoner can be seen opening and closing his hand.
- In the ViewMaster version of this episode, the accompanying story booklet has John use an electro-magnet to retrieve the Robot and get it into the ship before the nova explodes.