John Robinson was adrift in space after his safety line snapped when he left the Jupiter 2 to make vital repairs to the ship. Maureen suits went to rescue him, but both were trapped outside when the heat of a passing comet warped the hatch, preventing it from opening. At Will's suggestion, they were able to cool down the hatch using a fire extinguisher, and the boy's parents are able to reenter the ship.
While trying to determine the ship's position in space, Don picks up a signal from an approaching object. It turns out to be an enormous alien spaceship. Smith, alone on the lower deck, is convinced the ship has been sent by the foreign power that employed him to sabotage the Jupiter 2 mission, but when he attempts to make radio contact, he picks up only feedback. The ship does not respond to any of the Robinsons' attempt to make radio contact, but instead draws the Jupiter 2 inside it by some force the Robinsons are unable to overcome with the Jupiter 2's rockets.
The Jupiter 2 sets down inside the alien ship. John, Don and Dr. Smith go out to explore the strange and literally other-worldly ship. While John and Don attempt to extract information from what is apparently a navigational computer, Smith moves off to continue to look for his former employers. John and Don have some success, and are able to locate information on a nearby habitable planet.
Meanwhile, Will grows frustrated with waiting at the Jupiter 2, and contrary to his father's explicit orders, he ventures outside the ship to explore. He soon encounters a member of the alien crew, a blob-like creature that appears to 'speak' with electrical discharges. While Will is trying to establish communication with the creature, Dr. Smith arrives and chivvies him on. As it slowly dawns on Smith that these creatures are the crew of the ship and that it is not an Earth ship at all, he reacts in frustration and shoots the creature with whom Will was talking.
More of the creatures stir into action after the initial creature is shot, and they pursue Dr. Smith and Will through the ship. John and Don hear the disturbance and join Smith and Will in retreating back to the Jupiter 2. Even when they make it safely back to their own ship, the cannot escape—the outer hatch of the alien vessel remains firmly closed. John remains outside the Jupiter 2 long enough to use his laser to force an opening large enough for the Jupiter 2 to pass through.
Back in flight, the Jupiter 2 sets course for the planet found by John and Don in the alien records. Because the ship is in need of repairs possible only under gravity, they must soon set down, but John refuses to land until the planet has been reconnoitred. Conditions there may be too dangerous.
- The nucleus of a comet is made of ice and dust and is very cold. The writers of Lost in Space portrayed it as a blazing hot hazard. This is a huge inaccuracy.
- This episode portrays an encounter between the Jupiter 2 and an alien spacecraft in deep space. Unfortunately, this apeallingly dramatic senario is implausible. To reach another star in a reasonable amount of time, a starship would need to travel at an appreciable fraction of the speed of light, and on a precise trajectory aimed at its destination. Even if the galaxy is teeming with spacefaring alien civilizations, interstellar space is so huge that the probability of two spacecraft encountering each other, traveling at the same speed and on the same trajectory in deep space is infinitesimal. Changing speed and trajectory to match that of another ship would require huge amounts of energy, and would sacrifice the ship's ability to reach its intended destination.
- This episode marked the first portrayal of extraterrestrial intelligence in Lost in Space. To their credit, the writers plausibly envision aliens that are non-human and communicate by electrical discharges (as do electric fish in real life) and lack all knowledge of the English language.
- There is no teaser scene before the opening credits.
- Early on in various episodes,John Robinson is seen narrating a ships log. Unfortunately, this aspect of the series was dropped in the beginning of The Oasis, with only a brief quote of the log being used in One of Our Dogs Is Missing.
- The final new footage from the Alpha Control two-story set is seen, along with a brief, low quality shot of the facility's exterior.
- The shot of the Jupiter 2 approaching Priplanus (and a revised appearance), and part of the opening scenes at Alpha Control constitute the pilot's footage used in this episode.
- Will's and Smith's actions come under scrutiny a year later when the Robinsons are indicted for assorted offenses and put on trial in The Prisoners of Space.
- The interior of their derelict starship consists of sets left over from the movie Fantastic Voyage.-mainly the brain tissue sequence at the end of the film. They were lit much darker here,to make the set unrecognizable and more alien and mysterious. The Jupiter's capture by the derelict spaceship is shot using several different models and is a wonder of special effects. No expense was spared in filming this sequence and it shows the derelict's interior is obviously leftovers from the Jonah and the Whale episode of Voyage to the Bottom of the Sea, itself using sets borrowed from the film Fantastic Voyage.
- This episode's musical score is unusual in that little of it was repeated in later episodes. Aside from the famous 'Family Theme', 'Frontal Robotomy' and the moody 'Derelict Title' which plays over the last shots of Alpha Control, the other parts of the score were dropped completely. (Occasional excerpts of 'The Treatment/Swallowed' and 'Rescued from Space' are the only others to appear). For Lost in Space this is an anomaly given that almost all the show's music was repeated continuously throughout the three seasons.
- When the Bubble creatures are chasing the Robinsons to the Jupiter 2, the white shoes of the stage hands pushing the creatures occasionally come into shot.
- The bubble creatures are truly alien, amorphous blobs. They have no appendages nor any mechanisms to help them hold or manipulate objects. How they could build or operate a spaceship is a mystery, especially since the ease with which Prof. Robinson and Major West can decipher and operate the controls suggests they were ergonomically designed for humanoids.
- The plot of the Jupiter 2 coming across a derelict spaceship was reused for the Lost in Space 1998 film, although the inhabiting creatures in that version were not colonist Bubble Creatures but evil metal spiders. Also this derelict known as "the Proteus" was of human construction rather than of Alien Construction.
- When Professor Robinson is using the rescue line to return to the ship, you can see that it is a simple piece of yarn in addition to the wires that are holding him up. The yarn can be seen all bunched up and out of place.
- When Professor Robinson is firing his laser to open the derelict spaceship's outer doors at the end of the episode, you hear the laser, and see the sparks where the laser is striking the wall of the derelict spaceship, but the special effects people forgot to add the laser beam itself to the film. Also, firing the laser at the doors could weld them close, sealing both them and the Robinsons' fate.
- Not sure how Professor Robinson expects to get the J2 through a single downward cut into the "clamshell" doors, and wouldn't a cut in the doors breach the hull?
- The idea that our space pioneers would be unable to get a fix on a nearby star is unlikely. the nearest star is Proxima Centauri about 4.22 light years away, an the nearest Sun-like stars are Alpha Centauri A and B which are about 4.3 light years away, which is about 25 trillion (25,000,000,000,000) miles away. Even if the ship traveled at the speed of light for eight hours it would only be about 5 billion (5,000,000,000) miles away. Not being able to spot Alpha Centauri given these distances is the equivalent of not being able to see something a mile away by simply raising your height by about a foot.
- The landing and escape minature sequences with the Jupiter 2 are skillfully done, of a much higher quality than other network science fiction programs both earlier and contemporary.
- The derelict vessel was later re-used as the prison ship "Vera Castle" in the Season 3 premiere, Condemned of Space.
- This episode has the best of the Jupiter 2 engine sound effects of the entire series during the scene when the Jupiter 2 enters the derelict ship.
- When trapped outside the Jupiter 2, John pounds on the hatch while Don pushes from the inside. Aren’t these two acts working against each other?
- Why does everyone seem to pronounce “Alpha Centauri” differently?
- After sending everyone to bed, John makes rounds to check on them. He enters everyone’s room in turn, each time without knocking. Isn’t that a bit rude?
- Judy brings Don a drink. He thanks her, and shoves it aside and never touches it.
- Just as a side note, this is the only episode in which we hear Smith’s “evil laugh.” It’s a terrible shame, because that laugh is cool!
Next episode: Island in the Sky