Someone has been stealing vegetables from the hydroponic garden at night and Dr. Smith sets up an alarm to catch the culprit. He and Will camp outside and wait, and when Smith’s alarm goes off, they get up to see who is there. The thief turns out to be a very aggressive boy who seems to be spoiling for a fight. John and Don come out to question him, and the boy introduces himself as Quano. Quano challenges Will to a fight and then goes on to make comments about women that the Robinsons find demeaning. Maureen offers him supper and a warm place to sleep, but he refuses their offer of hospitality and leaves.
The next day, Quano reappears and stares at them. He believes Earth people are stupid and weak, especially the females. Quano informs the Robinsons that his father is the Leader of his planet, and that he himself is a prince. Doctor Smith gets very excited and tries to ingratiate himself Quano, but the boy will have none of it. Quano invites Will to go hunting with him, and as they walk, Will stops to examine rocks. Quano makes fun of such pursuits and tells Will that he has come to their planet to test his strength and bravery. He takes Will to a nearby cave where a monster lurks. Quano calls to the monster so they can fight it, but as it comes toward them, Quano trips on a rock and is knocked unconscious. Quano’s father arrives in time to save them and commends Will for his bravery and for going back to help his injured son in the face of danger, but the humiliated Quano becomes jealous and angry.
Later, Quano and his father visit the Robinson campsite. Smith immediately begins to ingratiate himself, but both Quano and his father find him disgusting and dismiss him. Quano’s father, the Leader, as he is called, meets John Robinson and is pleased and impressed by his leadership and strong handshake. The Leader asks that Will be permitted to compete in a contest with Quano. John initially refuses, but Will becomes irritated with the Quano’s teasing and accepts the challenge on his own. Maureen does not approve, but her husband talks her into it.
That night, Dr. Smith sneaks over to the alien camp to spy on them. He overhears the Leader warning his son that he absolutely must beat Will in the competition, for if Quano loses, the Leader will be forced to kill all witnesses to his shame... again. Smith is horrified and decides that he must ensure Will does not win. The next day Smith starts Will on a strict regimen of exercise, although he actually plans to exhaust will so that he will lose the contest. Don realizes what he is doing and puts a stop to it, thinking Smith is just being inept or cruel.
Quano arrives and informs the Robinsons that the challenge will start at dawn. If they fail to arrive, it will be taken as an act of cowardice and a the family will suffer a penalty. Smith tries to bribe Quano into taking him back to Earth, but the boy thinks Smith is a traitorous scoundrel and orders him never to speak to him again. When morning comes, Smith, John, Don and Will to go the competition. The challenge begins with a test of strength in which Quano proves to be the victor. The second challenge is a test of fear, followed by a test of dexterity, and a test grip. By the time the final challenge is at hand, the two boys are tied. Dr. Smith makes one last attempt to ensure Will does not win by trying to convince him to throw the contest, but Will refuses to cooperate. The Leader also has a talk with his son. He does not think Quano is doing well enough, and that Will will be victorious. Since the Leader has no desire to have to kill the Robinsons, he insists that the last contest be between himself and John Robinson. The two men duel with electric swords, and although the battle is close, John wins in the end.
The Leader tells Quano there is no shame in losing, but as he is congratulating John, Quano runs off. Will says that he thinks that Quano was hurt by his father’s lack of trust and has run off to the monster’s cave in order to prove himself a warrior. The Leader rushes to his son’s side and together they face the monster. The Robinsons leave them to share the moment in private and return to the Jupiter 2.
- For the stunts performed during the scene with the Volta Blade duel between Professor Robinson and the Alien King, Guy Williams needed no stunt double, as in all episodes involving fencing. Williams, of course, was an accomplished duelist after his time on the tv show Zorro.
- The Volta blade apparatus would be reused in a considerable number of later episodes as various forms of alien equipment.
- There is a common misconception in the beginning of this episode that Quano's hurled spear shattered the Jupiter 2's viewport due to the crash of glass. The sound was actually the spear crashing to the ground after hitting the set- it would be strange if a spear managed to break the glass which had survived meteor hits.
- When Will and Quano are walking along and about to enter the cave, Bill Mumy gets his foot tangled in one of the prop vines on the floor of the set. He shakes it off without missing a beat, and keeps walking.
- Yet another warrior alien race is encountered that uses physical combat in order to establish social rank (as in "Hunter's Moon," "The Deadly Games of Gamma 6," and "Follow The Leader.") It seems Earth is unique in the galaxy in using schools, written tests, elections, debates, and the other rules of participatory government
- Features the first occurrence of the Robot's laughter, that which he says is "only [his] computers being cleared" when Dr Smith asks what else "do we have to do" for work.
- Goofs - During Professor Robinson's "Volta Blade" duel with the Leader, he splits a tree in half with his sword. One half of the large tree falls on the cord of his electronic sword, completely trapping it. In the next shot, the cord has come "untrapped" from the tree and is again swinging freely.
- Why does John just stand there silently as Quano makes all those rude, sexist remarks to his wife and daughters?
- The normally sweet and polite Penny goes absolutely wild on Quano after he makes a chauvinist comment.
- Doctor Smith invents an alarm system to catch a thief, and it works perfectly! This surprises me, because in most cases Smith’s projects explode.
- So... The Ruler just decided he didn’t have to kill the Robinsons after all? I’m assuming he made that decision when he told his son “There’s no shame in defeat,” but he never directly said that he’d changed his plans.
- Where did the castaways get a treadmill or a baseball cap and sweatshirt?
- When Smith and the Robot were chatting while waiting for Quano to walk by, you can see the Robot's left claw vibrate whenever he speaks.
- Quano is, of course, played by a very young Kurt Russell who would, 32 years later, go on to star in the movie "Soldier" where he played a battle hardened...soldier...that was bred and raised to fight but eventually must learn about his humanity.
- It is implied that Quano is not more than a year, or two at the most, older than Will. Kurt Russell was about to turn 15 when the episode was filmed and Billy Mumy was about to turn 12.
- The Ruler is played by Michael Ansara, who is also known as the Klingon "Kang" from Star Trek, Star Trek: Deep Space Nine, and Star Trek: Voyager. He is one of 11 actors to have played the same character in three different Star Trek series (reference: http://en.memory-alpha.wikia.com/wiki/Michael_Ansara)
- This Episode was repeated on Thames Television on March 7th 1969
- This Episode was repeated on Granda Television on March 27th 1969