The episode opens with a performance of Macbeth on Planet Q attended by Kirk and an old acquaintance of his, Doctor Thomas Leighton. Throughout the play, Leighton urges Kirk to pay attention to Anton Karidian, the actor playing Macbeth: Leighton is sure that he is actually Kodos The Executioner. (No, not THAT Kodos.)
After the play, Kirk is pretty angry with Leighton since the latter claimed he had some sort of new food concentrate to end a famine, causing the former to divert the Enterprise three lightyears off course. Leighton claims he and Kirk are two of the nine people alive that can expose Kodos and is insistent that Karidian is him, since Leighton cannot forget the voice of the man who horrifically disfigured him. Kirk will have none of it, claiming Kodos is dead and leaves, wondering what the hell he's supposed to write in his report.
The story of Kodos is revealed gradually over the course of the episode: 20 years ago, both Kirk and Leighton resided in the Tarsus IV colony, of which Kodos was the governor. When a fungal infection destroyed most of the colony's food supply, the colony's 8,000 residents faced starvation. Kodos responded to the crisis by having half the colonists executed, using his personal eugenics theories to select who would live and die. Eventually supply ships arrived much earlier than predicted, making all those deaths utterly pointless. All that was found of Kodos was a body burned beyond recognition, and he was declared dead.
Kirk decides to go over a photo record of Kodos, and notes his similarity to Karidian. He also finds that there are no records of Anton Karidian older than 20 years, the same time as Kodos' "death". Intrigued, he decides to stay on the planet a while longer and attend a party Leighton is giving hoping to trap Karidian.
At the party, he finds that Karidian isn't attending but his daughter Lenore is. Kirk turns on his usual charm and they go for a walk, during which they stumble upon Leighton's dead body. Kirk is now determined to get to the bottom of this: he calls in a favor with the captain of the ship Karidian's troupe was meant to take off world to make it leave with no prior notice, stranding them there. Lenore then asks Kirk to give them a lift, just as he planned. Kirk accepts, in return for a "special performance".
Kirk then uses the ship's computer to look up the identities of everyone who met Kodos in person other than himself. One eyewitness is Lt. Kevin Riley, whom you might remember as the terrible singer from "The Naked Time". Despite having been recently promoted, he orders that Riley be reassigned to his former position, presumably to protect him. He also gets closer to Lenore, though whether it's to get more information on her father or it's just Kirk being Kirk is up for the viewer to decide.
Meanwhile, Spock is getting suspicious about Kirk's recent behavior and decides to investigate. He manages to figure out the Karidian/Kodos situation thanks to the ship's computer and reports his findings to McCoy. Spock also discovers that of the 9 people who could identify Kodos, only Kirk and Riley are still alive. Worse, all the others died in mysterious circumstances... and always in relative proximity to Karidian's theater troupe.
Speaking of Riley, he's not taking his reassignment well. While distracted by Uhura playing him a love song on comms at his request, a gloved hand sprays an industrial lubricant in his drink, poisoning him. Luckily Uhura hears his cries, and he's transported to Sickbay in time to save him. Spock urges McCoy to save Riley, since if he dies, then Kirk is certainly next.
Riley survives, and Spock and McCoy finally decide to confront Kirk. Kirk doesn't like "meddling in his personal affairs" but as Spock points out, this affects the functioning of the ship and thus is their concern. However, he does agree that all the evidence points to Karidian being Kodos. McCoy then starts questioning Kirk's motives:
This dramatic exchange is interrupted by the loud hum of an overloading phaser, which would blow up the entire deck. After finding it and disposing of it, Kirk finally has enough and confronts Karidian. After getting evasive upon being asked if he is Kodos, Kirk makes him read an execution order which Kodos read several times to use as a voice match. Karidian starts reading but eventually keeps going, barely glancing at the paper, as if reciting the words from memory. Nevertheless he is still evasive, though he mentions that "Kodos" might be considered a great hero if the supply ships hadn't come. He asks Kirk why doesn't he kill him now if he's so sure he's Kodos, to which he replies it would change nothing. Karidian mentions how tired he is of life and that he no longer treasures it, not even his own. He ends the conversation with this:
Lenore then enters and asks Was It All a Lie?. Kirk says it was initially, but not anymore. Lenore calls him merciless and storms off.
Meanwhile, Riley overhears McCoy talking about how Karidian is suspected of being Kodos. Since Kodos murdered Riley's family, he hatches a plan for revenge.
Spock tells Kirk that Karidian's voice is a match, but Kirk isn't convinced, since it's not an exact match and there's a man's life at stake. They then receive news that Riley has gotten out of sickbay and stolen a phaser. They head towards the ship's theater where the "special performance" of Hamlet by Karidian's troupe is taking place.
Kirk finds Riley getting ready to shoot Karidian from backstage, but talks him into dropping the phaser. Karidian and Lenore arrive backstage and the former finally comes clean and explains to Lenore that this is a result of the "part he played long ago" that he never told her about that has resurfaced. At this Lenore decides to drop the bombshell: she knew all along that Karidian was Kodos and she was the one who killed all the witnesses, including Leighton and the attempt on Riley, all to protect her father. She grabs a phaser and points it towards Kirk. Karidian, completely horrified at what his daughter has become, takes the shot meant for Kirk. Lenore breaks down in tears and is led away.
Later on in the bridge, McCoy mentions how Lenore will be taken care of. Apparently she has gone completely insane and thinks her father is still alive, giving performances to cheering crowds. When McCoy asks if Kirk really cared for her, he refuses to answer and the episode ends.
The Conscience of the Tropes:
- Absentee Actor: Scotty and Sulu are absent from this episode.
- Alas, Poor Villain: Lenore breaks down in tears after having accidentally shot and killed her own father before she is taken away.
- All for Nothing: The massacre that got Kodos the moniker 'The Executioner' happened when the colony he governed lost most of its food supply. The remaining food wasn't enough to hold until ships bringing food relief were expected to come, so he killed half of the 8,000 colonists according to personal eugenics theories, making a hard decision so that at least some colonists would survive. And then the relief ships arrived early, meaning nobody had to die at all.
- Lenore trying to ensure her father doesn't get identified by witnesses who saw him only leads to him getting noticed, and when she tries to prevent his arrest she accidentally shoots him when took a shot aimed at Kirk.
- Beard of Evil: Kodos the Executioner had one. He shaved it when he changed his name to Anton Karidian.
- Berserk Button: This is one of the first episodes to introduce the Federation's hatred of eugenics. It would become much more clear in Space Seed.
- Bewildering Punishment: How Reilly views his reassignment to Engineering.
- Catch the Conscience: The reason the quote from Hamlet was used.
- The Chains of Commanding: "The chain of command is often a noose."
- Character Development: When we last saw Riley in "The Naked Time", his most prominent traits were being able to lock everyone out of Engineering and singing a horrible rendition of "I'll Take You Home Again, Kathleen". Here he's given a tragic Backstory and Revenge as a motivation. Interestingly, this was accidental - originally the character whose family died at Kodos's hands was a completely different person. However, the casting director unknowingly cast the same actor who had played Riley in that role, and they just went with it.
- Cold Equation: Kodos the Executioner/Anton Karidian used this as his excuse to execute half the colonists of the Tarsus IV colony when a fungus destroyed most of their food supply. It's worth noting that the only reason it counts as this trope was because he was wrong about one of his assumptions: it turned out that the Federation did manage to get relief supplies to the colony in time. Had he turned out to be right...
- Cope by Pretending: After she accidentally kills her father, Lenore's already dubious sanity shatters completely, and she clings to the delusion that he's still alive performing to cheering audiences.
- Cry into Chest: Thomas Leighton's widow, Martha, briefly clings to Kirk as she weeps.
- Daddy's Little Villain/Evil Parents Want Good Kids/In the Blood: Karidian is distraught once he realizes his daughter is killing people for him, having thought that she was the one part of him which remained untainted by his past.
- Dark Messiah: Kodos took control of his colony during a famine, killing off half the population to save the rest. He never really apologizes for it, either; had the food supply ships not chosen that inconvenient time to appear, Kodos might be hailed as "a great hero!" The carnage was needless but the conspirators didn't know that at the time. To save face (and coincidentally his skin), he faked his death and went underground.
- Death Ray: One of the few times that a phaser kills someone without vaporizing the body.
- Despair Event Horizon: Lenore's confession drives Karidian over the edge into anguished guilt.Karidian: Oh, my child—my child...*sobs* you've left me NOTHING!!!
- Does This Remind You of Anything?: Kodos culled people based on his eugenics theories, and has lived under an assumed name to escape the punishment for his crimes decades later. The comparisons to the Nazis (especially in the '60s when knowledge of the many fugitives living underground became prominent after the capture of Adolf Eichmann) are probably intended.
- Drinking on Duty: Spock struggles to get Bones to focus on the topic at hand due to the latter hitting the sauce pretty hard during a quiet time in Sickbay. Possibly also a case of Values Dissonance, since by present-day standards a doctor drinking in a medical facility, even if off-shift, would be seen as pretty egregious.
- Early Installment Weirdness: McCoy casually mentions that Vulcans were a conquered species. This is the only mention of any conquest of Vulcan; future episodes and series would firmly establish that Vulcans have been a more advanced species than most for centuries. Furthermore, Spock states outright that Vulcan has not been conquered within its collective memory in "The Immunity Syndrome".
- Easily Overheard Conversation: Uh-Oh! Riley just heard Bones talking to his computer! Why did they phase out the keyboard again? Though twentieth-century doctors often dictated their notes to save time, it is shocking that by the 2260s they haven't come up with something better.
- Even Evil Has Loved Ones: Karidian clearly loves his daughter, and is disappointed to find out she's been killing innocent witnesses on his behalf - he didn't want his crimes to affect her.
- Evil Redhead: Kodos when he was younger. As Karidian, his hair has grayed and his personality is much more mellow.
- Explosive Overclocking: A phaser rigged to overload is placed in Kirk's quarters. He and Spock tear the room apart to find it, because if it blows it'll take out half the deck.
- Face-Revealing Turn: We are introduced to Thomas Leighton. We only see the right side of his face for five minutes, until he says that he survived a massacre by Kodos the Executioner, at which point we see that the left side of his face is covered by a patch.
- Fake-Out Opening: A bloody dagger? In a sci-fi show? Turns out they're just watching a production of Macbeth.
- Femme Fatale: Lenore gives a hint of her true intentions when she compares herself to Cleopatra VII and Kirk to Julius Caesar. Before long, she does reveal that she is indeed "green in judgment, cold in blood."
- Future Food Is Artificial: Riley is served a lunch that looks composed of Jolly Ranchers. Yeah, that's a color found in nature. He might've liked it better if Lenore hadn't spritzed 409 into his chocolate milk.
- Hand of Death: The opening shot of the episode. Goodbye, King Duncan.
- Heel Realization: Karidian had one of these a long time before the episode began. Look at the abject horror on his face as he rereads the words he spoke as he sentenced thousands to death. Or, even before that, his cryptic reply to Kirk:Kirk: You're an actor now. What were you twenty years ago?Karidian: Younger, Captain. Much younger.
- I Did What I Had to Do: Kodos never apologizes for his actions, arguing that he'd be seen as a hero had the rescue ships not arrived early.
- Incestuous Casting: In-universe, Anton Karidian plays Macbeth and his daughter Lenore plays Lady Macbeth.
- Kick the Dog: Just to make sure we don't think the massacre was a Shoot the Dog situation that went horribly wrong, they mention that Kodos used his own theories on eugenics to select who got spared and executed, instead of a fairer/more pragmatic method such as a lottery.
- Knight in Sour Armor: Perhaps Lenore's accusation "There's a stain of cruelty on your shining armor, Captain." isn't far from the truth.
- Large Ham: And for once, it's not Kirk, who is (understandably) a bit subdued in this episode, but Karidian, who easily matches Kirk's normal standard of ham. It's most blatant when he's onstage, but it comes out at other times as well.
- Lenore too, when she reveals how insane she truly is.
- Laughing Mad: Lenore loses her marbles after the phaser hits the wrong man. Actually, a bit before that. But once Karidian dies, she checks out for good.
- Leave No Witnesses: The motive behind the recent murders. It almost leads to a variation of Nice Job Breaking It, Herod!, as Riley is ignorant of the danger until he's poisoned, thus allowing him to find out who's on board and trying to kill him.
- Literary Allusion Title: It's part of a line from Hamlet, where the title character plans to see if Claudius really did kill his brother by watching his reaction as he sees the murder scene reenacted in a play within a play.Hamlet: "I'll have grounds More relative than thisthe play's the thing wherein I'll catch the conscience of the King."
- Love Makes You Evil: Lenore's devotion to her father has made her unapologetically willing to murder anyone who could possibly reveal the truth about her father's identity. She is completely dismissive of their lives having any value whatsoever, since they are "dangerous" in that they could identify him. To protect him, she has been systematically murdering each of the surviving witnesses no matter where they were.
- Mad Artist: The Karidian Company. The script hints that "Anton" gravitated toward acting to get away from the "ghosts" and assume new identities. ("I play many parts.) His daughter is a few fries short of a Happy Meal herself.Lenore (of the ship) It will become a floating tomb, drifting through space with the soul of the great Karidian giving performances at every star he touches.
- Missing Mom: There's no mention in the episode of Lenore's mother, what happened to her, or whether she also knew that Karidian was in fact Kodos.
- Moral Myopia: Lenore challenges Kirk's right to judge Kodos for committing the massacre of 4,000 people — an event Kirk himself actually lived through and witnessed. Lenore herself had not even been born yet at the time of the massacre, and is thus judging the entire matter based solely on her love for her father, with no concern for the thousands that were executed or for the surviving witnesses she herself has been murdering in order to protect his secret identity.
- More Hero Than Thou: When they discover that an overloading phaser has been hidden in Kirk's quarters, Spock and the captain briefly have an argument over who should escape from the room and who should take the risk of staying to find it.
- Names to Run Away from Really Fast: Kodos the Executioner.
- The Needs of the Many: Kodos' rationalization for all the people he killed. It turned out to be a Senseless Sacrifice.
- Never Found the Body: Well, there was a body, but it was never positively identified as Kodos.
- Not So Stoic: When Spock discovers what Kirk is trying to hide, namely that he survived an infamous mass-killing as a kid, and that the man responsible may be aboard Enterprise, he becomes extremely animated, much to Bones's amusement.
- Parents in Distress: Lenore sees herself as just protecting her father.
- Please Wake Up: After Lenore's attempt to kill Kirk instead kills her father when he blocks the shot, her mind snaps and she starts begging him to wake up. According to Bones' final report, she clings to the delusion that he's still alive.
- Power Is Sexy: Lenore thinks so. "And this ship. All this power. Surging and throbbing, yet under control. Are you like that, Captain?"
- Reassigned to Antarctica: Riley believes being demoted back to Engineering is this, when in reality Kirk wanted to protect him from the murderer.
- Red Alert: When the overloading phaser is discovered in his cabin, Kirk, for the only time in the series, orders Double Red Alert. Justified, in that the expected explosion was only seconds away.
- Red Oni, Blue Oni: Spock and Bones, per usual. This time, Spock is Red, certain that Karidian is Kodos and urging action, while Bones is Blue, arguing that they don't know for certain and Kirk could be making a terrible mistake.
- Retired Monster: Kodos the Executioner, a notorious tyrant who had murdered thousands in a massacre decades before the date of the episode. The true villain of the episode, however, is his daughter, who tries to kill every remaining witness of the crime - this includes Kirk - to prevent her father from being arrested for it; Kodos dies when she tries to kill Kirk, taking a phaser blast meant for him, making him a somewhat tragic figure as his past crimes not only catch up to haunt him but to destroy the one thing in his life he had hoped to keep pure and untainted.
- Revealing Cover-Up: Leighton's claims regarding Kodos might have gone unheeded had Lenore not murdered him, and then tried to kill Reilly.
- Shoot the Shaggy Dog: The culling of 4,000 people was to prevent the population from starving, but the relief supplies came early.
- Shout-Out to Shakespeare: Two of his plays are partially acted. References are made to Julius Caesar, Antony and Cleopatra and As You Like It, while the title comes from Hamlet. This marks the first mention of Shakespeare in the franchise, and the first episode title to quote a Shakespeare work, marking the beginning of a very long association of Star Trek with the works of the Bard.
- Shut Up, Kirk!: Karidian appreciates neither Kirk's claims that he is Kodos the Executioner, nor Kirk's eagerness to judge Kodos's actions with the benefit of hindsight:Karidian: If you're so sure that I'm Kodos, why not kill me now? Let bloody vengeance take its final course! And see what difference it makes to this universe of yours.
- Stepford Smiler: Lenore speaks of her evil deeds with a chipper smile on her face. Pity things ended when they did. She would've made a good Ophelia.
- Stupid Evil: Lenore is murdering people who can identify her father, a poorly thought out plan which only draws more attention to him.
- Survivor's Guilt: A deleted scene would have Kirk reveal to Spock and Bones that the only reason why he escaped execution was because he met Kodos' eugenicist standards. Even in the finished episode you can sense hints of Kirk's guilt.
- Taking the Bullet: Lenore fires her stolen phaser at Kirk. Kodos jumps in front of him and takes the blast.
- The Teetotaler: Spock boasts how Vulcans never drank alcohol (what he says exactly is that Vulcans lack a weakness to alcohol). Bones doesn't see it as much of a bragging point.
- Theme Tune Cameo: A slow, muzak-esque version of the classic theme plays in the background at Leighton's party.
- Title Drop:Lenore (raving) There's no time to sleep. The play. The play. The play's the thing, wherein we'll catch the conscience of the king.
- Two-Faced: Leighton is missing half his face, along with an eye. Ironically he is one of a few eyewitnesses who can identify his attacker by sight.
- Unlimited Wardrobe: Lenore ties with Edith and Khan for the most costume and hair changes (six). Unlike the Depression-era "slum angel" and the refugee fleeing from Earth on a sleeper ship, she at least has a very good excuse (she's an actress).
- Villainous Breakdown: Lenore after revealing she had killed seven of the nine witnesses who knew her father as Kodos the Executioner ran out to the stage with a phaser, trying to kill Kirk, one of the witnesses. The mad glint in her eyes told us that she lost her mind. And when she accidentally killed her father, she broke down into tears and later on, she insistently believed that her father was still alive and still performing.
- Villainous BSoD: Lenore suffers two - one when she confesses to her crimes, ranting that she had eliminated all the "ghosts" of his past, and again after she shoots her father by accident. She sits over his body, crying that he needs to wake up because it's time to perform.
- What the Hell, Hero?: Bones tries to save Kirk from becoming He Who Fights Monsters with "Do you play God? Carry his head through the corridors in triumph? That won't bring back the dead, Jim!" Kodos also gives his daughter a rhetoric "What have you done?" when he realizes that she's been killing people to protect him.
- Whole Plot Reference: In addition to the title, this episode shares many plot elements with Hamlet: a leader's troubled conscience, his crimes being exposed during a play, and a daughter going insane (or more so, in Lenore's case) after the accidental killing of her father. Lenore recites the lines leading up to and including these over her father's body.
- You Killed My Father: Kirk has to talk Riley out of shooting Kodos, who had killed Riley's parents. In an odd juxtaposition, this happens while Kodos is playing the Ghost of Hamlet's Father, who is telling his son to avenge him (incidentally, in many productions of Hamlet, the actor who plays the Ghost also plays Claudius. That would explain why Lenore could insist that he still has a role in the play to finish).
- You Owe Me: Kirk calls in a favor to a passenger ship captain, telling him to skip picking up Karidian's acting troupe so that they have to hitch a ride on the Enterprise.