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Violating orders, Doctor Smith has grown an alien plant in his cabin. Space radiation turns it into a monstrous mutant that thinks he's its “mother!” Ordered to dispose of it into the jets, Smith instead lazily flushes it out an airlock, and it promptly attaches to the ship, causing engine problems! To remove the plant, John proposes a close passage through the dense atmosphere of a nearby planet – but that planet is inhabited, and the residents do not want visitors. The Jupiter 2 lands anyway, and then discovers that the planetary inhabitants demand a high price for their safe departure!
Will: Doctor Smith, I'm not sure that's an orange tree.
Doctor Smith: Of course it's an orange tree. Any day now a crop of sweet Valencia oranges will burst forth!
The Robot: (about Doctor Smith) I have computed his condition. The good doctor is only paralyzed with fear!
Doctor Smith: Why shouldn't I be? There's just so much a man can stand!
Judy: We've been traveling in space for hours! How could a plant attach itself to the spaceship?
John: That's a good question, Judy.
Sobram: You are about to enter a restricted zone. Alter your flight pattern immediately. Leave the area. We repeat – this is a restricted zone.
John: This is John Robinson of the planet Earth. We're having some trouble up here.
Sobram: A final warning: leave this are at once! Do not attempt to enter out atmosphere, or you will be destroyed!
Don West: We're still trying to make contact with the planet. So far, no luck. Something has to be done, and we have to do it.
Doctor Smith: Did you say 'we,' Major?
Don West: Someone has to go down to that planet and convince them we're not their enemies.
Doctor Smith: And how do you propose to accomplish this miraculous mission? Do we grow wings and fly?
Don West: No. By using the space pod we can get to the attack area before the Jupiter 2. You see, the pod's small enough to go undetected.
Doctor Smith: That's a splendid idea, Major! I suggest you go along, and my blessings go with you.
Don West: I'm glad you approve, Doctor Smith. Because you're going with me.
Don West: Which would you rather face, Smith? What's inside there, or me?
Doctor Smith: Let us proceed.
Sobram Book: Hear, then, the story of this ancient world. In the beginning the planets fought among themselves. For ten thousand years, civilizations battled with each other. And then, the Sobrams appeared – a race whose sole enjoyment was the making of war. They had created an indestructible planet, capable of moving through the galaxy at will. But if the world of the Sobrams was indestructible, they themselves were not. They fought to their own extinction. Now, nothing remains of this warrior race except this world, and the history you have heard.
Sobram: The end of my life is near. But before it is over, there is a legacy I must leave.
Doctor Smith: Oh, my dear sir. I shall be more than happy to help you with your will. You see, as something of a legal brain, I can avoid all but the most complicated of probates.
Sobram: Yes, well, that's not what I meant.
Don West: Just what did you mean? And what is your legacy?
Sobram: One of you must stay behind and take over this planet. Either that, or you will all be destroyed.
The Robot: The alien seeks one thing: someone to play against him in one last war game. A game that eventually will destroy this entire world!
Don West: There's only one person I know who's totally without any standards.
(Don hauls Doctor Smith in front of Sobram.)
Sobram: Perhaps. He certainly has the sneaky look of a dirty fighter.