The Enterprise crew are headed off to the planet Ekos to pick up famed cultural observer John Gill, with whom the Federation has lost contact with for some time. In a bit of Hero Worship, McCoy and Spock share a poignant discussion about their relationship with the man, with Spock admiring Gill's take on historical events as causes and effects rather than that boring system of dates and events that normal history teaches us.
Things start to get interesting, though, when a nuclear interplanetary missile is launched at the ship from Ekos — technology that shouldn't even be possible for the planet's primitive inhabitants.
Taking high orbit over Ekos, Kirk and Spock beam down in local attire to see what they can find about this turn of events, only to be more baffled when a televised message reveals that not only is the planet an exact duplicate of Nazi Germany, but that John Gill is the planet's Führer. Ambushing a pair of Nazi soldiers in order to dress as the enemy, they attempt to infiltrate the Führer headquarters to get some answers, but are caught and brought in for interrogation. There, they meet a Zeon prisoner by the name of Isak, who explains that the planet had actually been a rather nice place to visit, during the initial rule of the Führer, but turned into a nightmare once the old Nazi prejudices came up - now the Ekosians are on their way to eradicating the inhabitants of their sister planet Zeon in much the same way the Nazis tried to eradicate the Jews and other hated minorities. Using crystal transponders embedded into their flesh, Kirk and Spock manage to free themselves and Isak, and escape into the underground that Isak is a member of. However, before they can prove to the underground that they're friendly, a Nazi task force led by a young woman named Daras — crowned a hero of the fatherland in the same transmission that revealed Gill as the Führer — comes in and shoots one of the underground, threatening to kill them all if they don't comply.
Kirk manages to overpower Daras, but is prevented from killing her by the man she shot; turns out, Daras is a member of the underground, and the raid was an elaborate test to see if Kirk and Spock are friendly. Deciding things are screwed up enough without worrying about the Prime Directive, Kirk comes out and tells the group that Gill is an alien sent to observe Ekosian culture, and that something has gone horribly wrong to make him interfere with the planet's development so radically. With the underground's help, Kirk and Spock break into the headquarters, once more, just in time to catch a televised message from Gill seemingly announcing a "Final Solution" to eradicate Zeon once and for all. However, with the help of a very reluctant (and late to the party) McCoy, they're able to determine Gill is actually being drugged and kept in a stupor; a quick Mind Meld further reveals his second in command Melakon has taken over, using him as a figurehead while he wields the real power behind the swastika.
With some drugs to help stimulate him into light consciousness, they're able to get an answer to the multi-million credit question: why did Gill break the Prime Directive and use Nazi Germany as a template for his interference? As it turns out, Gill just couldn't stand idly by as the Ekosian people were tearing themselves apart by their barbarism, and thought the efficiency of the Nazis could be used to civilize them, if malice wasn't put to the fore, and it worked until Melakon took over. Eventually, Kirk manages to get Gill lucid enough to cancel the Final Solution order before Melakon kills him, who is in turn killed himself. With the Nazi planet now leaderless, all the other Nazis just step down without a fuss, and it'll be a breeze for La Résistance and Zeon to reform a whole planet full of Nazis filled with anti-Zeon propaganda.
- Actual Pacifist: The Zeon are so peaceful that Isak worries that they'll fall to the Ekosians without a fight.
- Artistic License History:
Spock: What impressed me most was his treatment of Earth history as causes and motivations rather than dates and events.
- Spock's conception of History was already outdated in the '60s.
- Kirk repeatedly refers to the SS uniforms as "Gestapo," which was the plain-clothes secret police.
- Artistic License Military: Many of the Nazi uniforms have inaccurate or mismatched rank insignia compared to history. This could be chalked up to Gill not being too fussy about the finer details.
- Blatant Lies: The Nazis announce that one of their missiles utterly destroyed an enemy space ship - that ship being the very un-destroyed Enterprise.Kirk: You look quite well for a man who's been utterly destroyed, Mr. Spock.
- Broken Pedestal: Kirk is aggrieved to find that his teacher has become another Hitler. The pedestal is repaired when he gets out of his drug induced haze and denounces the regime, just before dying in Kirk's arms.
- Chairman Obvious: Chairman Eneg demonstrates his firm grasp of the obvious.Eneg: You are not from Zeon.
- Cycle of Revenge: Averted at the end - Melakon kills Gill, while Isak kills Melakon. When another soldier raises his rifle at Isak, Eneg stops him and declares "There has been enough killing."
- Dated History: It was often thought for a while after World War II that Nazi Germany was efficiently-run because of its fast ascension from military impotency, collapse of national morale, and economic devastation to a world power and scary conquering machine. As more and more research has been unveiled, the Third Reich has been shown to have sacrificed any hope of long-term efficiency in order to implement their short-term solutions, and even those needed to be augmented by expansion into the resources of Austria and Czechoslovakia to work. Ironically, this would perfectly tie it back in with their lebensraum attempt into Zeon.
- Defector from Decadence: Daras is working with the resistance because she believes the Nazi leadership has gone off the rails.
- Does This Remind You of Anything?: Gene's not too subtle about anything in this episode. The Space Nazis' scapegoats come from the planet Zeon (Zion) and have names like Isak and Abrom. The way Melakhon talks about how Spock's physical features are obvious evidence of inferiority also evokes Nazi eugenics.
- Dressing as the Enemy: Kirk and Spock steal the uniforms of two Nazis for a disguise. Unfortunately, they make a mistake in military protocol bad enough to arouse a Nazi officer's suspicions enough for him to order Spock to take off his helmet. When Spock's ears are exposed, both he and Kirk know full well they are screwed.
- Failed a Spot Check: Kirk and Spock walk right by a Gestapo officer that is standing in broad daylight and are then somehow surprised when he "jumps" out to capture them.
- Final Solution: The plan for a Final Solution is announced midway through the episode.
- Forgotten Phlebotinum: Gee those Transponders might have come in handy in any of the other 78 episodes in which the landing party's communicators get taken away.
- Human Ladder: Kirk and Spock make one in their escape attempt. Given that they've both been whipped, it's very uncomfortable for the captain.
- Idiot Ball: A massive one for John Gill for coming up with Fascism as the best way to peacefully unite a planet, while he already has an excellent example of one in the Federation itself (which has united Earth for centuries already). Though it's interesting to note it worked, as merely an efficient state rather than 'evil nazis', the latter of which only happened when Melakon drugged him and changed things. Even still, he himself notes in his dying moments that 'even historians can fail to learn from history'.
- Inexplicable Cultural Ties: Not the case, which is noteworthy because that is often forgotten in summaries of TOS, and because the fact that it looks like this is one of the main things that tips off the Enterprise crew that something is seriously wrong despite the fact that only four episodes later they will react to another planet being very similar to an Earth society (in that case The Roman Empire) complete with names and symbols by handwaving it as just an example of natural parallel development.
- I Owe You My Life: Isak, after Kirk and Spock escape with him.
- Know-Nothing Know-It-All: Melakon attempts to analyze Spock's unusual appearance based on the regime's racial theories and declares that he exhibits "a low forehead denoting stupidity" and "the dull look of a trapped animal". Big mistake.
- La Résistance: The Ekosians who disagree with the government's plan to wipe out Zeon.
- The Man Behind the Man/The Man in Front of the Man: Melakon, officially the Fuehrer's second-in-command, combines both tropes when he's revealed to be the one behind the Zeon purges.
- Man Hug: Isak shares one with his brother Abrom after his escape.
- Meaningless Meaningful Words: John Gill's New Era Speech. Spock points out that it follows no logical pattern.
- Meaningful Name: Zeon, clearly referring to Zion, the Jewish promised land.
- Mugged for Disguise: Two Nazi officers were nerve-pinched for disguises.
- Naked People Are Funny: When Kirk asks why Bones hasn't beamed down yet, he's told the Doctor is having trouble getting his Nazi uniform on. Kirk says "I don't care if you have to send him down naked, just get him down here!" Cue Kirk's reaction when he hears the transporter beam whine start immediately after this. (Don't worry...it was the boot the Doc was having trouble with.)
- Nice Hat: That toque covers Spock's ears so well. The stolen helmet from the S.S. agent also works, until he's told to take it off.
- No Endor Holocaust: The ending implies that there won't be any anti-Zeonite sentiments left under the population, and that the army leadership will politely step down from power. Given Earth's many examples of what can happen when a political dictatorship is decapitated (as both the puppet leader and actual leader die), things could have gotten ugly very fast. Mind you, a civil war may be bad but might help it ease out of Nazification.
- No One Sees the Boss: Because the boss has been drugged into catatonia, and The Dragon has taken over.
- No Swastikas: Averted.
- Non-Lethal Deadly Weapon: Daras fires a gun at Abrom and kills him. After Kirk and Spock grab her, Spock takes her gun away from her. Abrom then gets up, revealing that her gun was filled with blanks. Spock points the gun at Daras, even though it can't shoot her. Perhaps justified by the fact that even blanks can cause serious injury from the range he is threatening her with it. (And from the look on her face when this happens, she agrees.)
- Percussive Pickpocket: Kirk stumbles into a guard in a corridor; after apologizing and moving on, he reveals to his companions that he lifted the guard's keys.
- Planetary Nation: Melakon is trying to make the planet this.
- Planet of Hats: People from the planet Zeon are identified and arrested because they wear civilian clothes. All the Ekosians we see on screen are Nazi officials.
- Pseudo Crisis: Our heroes are surrounded by Nazis! (ad break) But they're with the resistance, so it's okay!
- Puppet King: Melakon keeps Gill drugged and only trots him out to deliver the occasional speech.
- Reports of My Death Were Greatly Exaggerated: While planetside, Kirk and Spock hear a news report claiming the Ekosians "utterly destroyed" the enemy spacecraft. Kirk jokes that Spock looks quite healthy for someone who's been utterly destroyed.
- Reverse Mole: Daras and Chairman Eneg are both introduced as loyal servants of the regime before revealing that they're working with the resistance.
- Sdrawkcab Name: Chairman Eneg, probably.
- Shirtless Scene: Kirk and Spock when they get whipped. Spock's scars are tinted green.
- Staged Shooting: Used to see which side Kirk and Spock are really on.
- Take a Third Option: When Ekosians launch the invasion fleet against Zeon, Daras, the Ekosian resistance fighter, pleads with Capt. Kirk to have the Enterprise destroy it to save Zeon, saying that the loss of Ekosian lives is the lesser of two evils. Kirk balks at that and manages to get Gill to cancel the invasion instead.
- Trojan Prisoner: A couple of times when Kirk and Spock (and later Kirk and Spock and Isak) don't have enough uniforms to go around, they use the "just taking this prisoner for interrogation" method to get past guard posts.
- Well-Intentioned Extremist: Yes, Gill actually had good intentions when he recreated Nazi Germany.
- Whip It Good/A Taste of the Lash: Kirk and Spock get the shit beat out of them.
- You Have Got to Be Kidding Me!: Kirk is exasperated when Spock's Blunt Metaphors Trauma keeps him on Kirk's post-whipping back for a little too long.Kirk: I...don't care if you aim at the broad side of a barn. Just hurry, please.
Spock: Captain, why would I aim at such a structure?
Kirk: (sighs) Never mind, Spock, just...get on with the job.