At the drill site, John and Don fall into quicksand, but Dr. Smith flees in terror rather than attempt to rescue them. Arriving back at camp, he tells the others of the situation and Will runs to the drill site with a rope to rescue his father and Don. John is so angry that he banishes Dr. Smith from the camp. When he leaves, Smith takes a bottle of deutronium fuel to ensure the Robinsons will not be able to leave without him.
Later, Will follows Dr. Smith to his campsite, where Smith reveals he has found some alien plants which seem capable of duplicating any object, though we soon discover that the duplicates are in fact vegetable matter and therefore useless. Smith accidentally spills the bottle of deutronium on the plants. The fuel affects the plants in a strange way: it causes them to become gigantic in size.
The next day Judy happens on the now enormous plants. She is somehow overcome with sleep and lies down in one of the giant flowers. Later, a vegetable clone of Judy appears in the camp to take her place and to obtain further deutronium for the plants. Her personality is quite unlike the real Judy's, but her family only thinks that she is in a bad humour for some reason.
The following morning, the Robinson awake to discover the monstrous plants have grown all the way up to the Jupiter 2 itself. The plant clone of Judy had been feeding them with the Robinsons' supply of deutronium. When they discover that Judy is in fact a plant, she reveals all.
Using ATI fluid, which they have in abundance, the Robinsons begin to destroy the plants, working toward the area where they believe their Judy can be found and saved. They are able to rescue her without incident and destroy the last of the mutant plants.
- The original title of this episode was "The Cyclamen."
- Cyclamen here on Earth are frost-sensitive, so the idea of freezing them to kill them is somewhat accurate.
- Why was Judy out wondering around alone in the middle of the night? Why did Judy just suddenly get the urge to take a nap in a gigantic open flower?
- We never know what happens to the cloned Judy. She just disappears.
- Marta Kristen has said this is her favorite episode because it gave her a chance to use more of her acting skills.
- This episode sees the only use of the Chariot's powerful neutron guns (possibly the strongest rifles in the Robinsons' arsenal).
- In the first season the alien planet's biosphere seems to be dominated by native life-forms that grow rapidly and either adopt the characteristics of a host or promote gigantism . Perhaps this was an adaption to the wild climate changes or an idea borrowed from "Invasion of the Body Snatchers."
- The plants' ability to mimic and reproduce another object is used as a device in John Varley's "In The Hall of the Martian Kings" where astronauts stranded on Mars are assisted by bio-engineered plants created by the long dead Martians who made them to help potential future explorers survive.
- The monster plants - and the method of dispatching them - is the same as seen in Welcome Stranger and The Space Croppers. *Why did Don take the fuel back from Smith, but allow him to keep the Robot?
- If Doctor Smith is such a gourmand, why does he consider cans of Pork & Beans to be “necessities of life?”
- If Smith knew that the supply of Deutronium could be the key to whether he got to go with the Robinsons or not, why did he act so carelessly with the bottle he had? He scattered a handful all over the ground and then didn’t even put the cap back on! No wonder it got eaten by a plant!
- When John and Don are dragged into the quicksand pit, they sink quite rapidly until it reaches their necks, when all of a sudden they conveniently stop sinking, as the quicksand reaches just above their necks.
- All of a sudden, the Robinsons have ditched the “plasma as a source of rocket propellant” explored in “The Raft” (ep 12). Now it’s all about the quest for deutronium as a fuel source.
- Though originally a stowaway aboard the Jupiter II, Dr Smith nonetheless has his own shaving kit and shaving lotion.
- In earlier episodes, constant reference is made of the Robinsons continuing the initial journey to Alpha Centauri, but here they only talk about returning to Earth.
- Why is Judy drawn to the evil plants? It is never explained.
- It’s inconceivable that the Robinsons would even consider, let alone agree to Dr Smith’s demands of being taken back to earth leaving Don, and the family left behind. Yet we see Well and Penny starting to move all of their stuff out of the Jupiter II. Boy, that could take weeks!
- Will: [having just rescued John and Don from the quicksand] “I'd have been here even quicker if Dr Smith had told me you were in trouble”. Don: “Now he's in trouble!”
- Will: “Too bad you couldn't find the deutronium, Dr Smith, but you shouldn't have tried to trick me”. Dr Smith: “I didn't just try, I succeeded. Let's not forget that!”
- Penny: “Well, if you do stay, could you tend to my garden for me”? Dr Smith: “Your garden will wither and die, I can promise you THAT”.