Ever since the events of "Birthright", Worf has been out of sorts. In the course of teaching young Klingons who hadn't been raised as Klingons about their own culture and beliefs, he's come to realize that he doesn't really believe those things anymore himself. So he plunges headfirst into Klingon spirituality, engaging in marathon meditation sessions and inhaling (presumably) mind-altering smoke, in the hopes of connecting with something greater than himself. Unfortunately now it's starting to affect his work performance.
After Worf explains himself, Captain Picard, ever the Reasonable Authority Figure, permits him to take some time off to get his head together. He opts to head to the planet Boreth, the most sacred place in the Klingon religion. According to Klingon scripture, before he died Kahless the Unforgettable, the great spiritual teacher and unifier of the Klingon people, pointed to a star and told his followers, "Seek me on that point of light." Boreth is the planet orbiting that star, and devout Klingons pray and meditate there waiting for his Second Coming.
Ten fruitless days of meditation later, Worf is about ready to pack it in (especially after a boy who just got there has a vision and he hasn't yet). But Koroth, High Priest of the temple, encourages him to stay a little longer. After all, the priests have been waiting 15 centuries; what's a few more days?
This turns out to be good advice. Shortly after returning to the shrine, Worf has a vision. Kahless himself appears before him, and beckons him to approach. Worf is overjoyed...then startled when he's actually able to touch Kahless. It's not a vision. He's real.
Kahless makes himself known to everyone at the temple, and tells a story about the origin of the batl'eth that the priesthood deliberately kept secret from the populace just for such an occasion. He claims that he has returned to the Klingon Empire in its hour of greatest need, to heal the fractures in the Empire caused by politics and infighting and lead it back to honor and glory. Worf tries to maintain a healthy skepticism despite his need to believe, going so far as to bust out his tricorder and scan Kahless's life signs (he's Klingon; that much he can confirm). Kahless, to his credit, takes this in stride, but when Worf persists in his skepticism Kahless finally engages him in combat. The fight ends in a draw, mainly because Kahless breaks it off before it's over to praise Worf for finally embracing his Klingon roots; Worf persisted in his convictions and showed courage in battle, rather than mere bloodlust, and that's what a Klingon should be. This is enough to convince everyone else at Boreth, but Worf is still unsure.
Meanwhile, word has reached the Klingon Empire about this purported Second Coming. The Enterprise has been asked to head to Boreth and pick up the alleged Kahless and escort him to the Klingon Homeworld. Furthermore, Klingon Chancellor Gowron himself is going to meet them halfway, and he's bringing with him a sacred relic allegedly stained with the blood of the original Kahless for DNA testing. The priests of Boreth are incensed by this act of sacrilege, but they can do nothing about it. And it turns out, they didn't have to worry. The DNA is a match. This Kahless is the Kahless.
The crew of the Enterprise puzzle over this development. Gowron, meanwhile, couldn't care less about the scientific evidence. He just assumes this whole thing is a power play by the priests of Boreth. He notes that divisions are starting to form in own ship's crew, believers versus skeptics, and that may be just what the priests want. Gowron points out that it's awfully convenient that "Kahless" first appeared to Worf, and right before he was about to leave Boreth for good. After all, if Koroth and his sect are looking to gain some serious political clout, they couldn't do much better than having the illustrious Worf, Son of Mogh, on their side.
For his part, Worf is caught in the middle. He desperately wants to believe that this is really Kahless, but he knows logically that it doesn't make sense. Furthermore, the more time he spends around Kahless, the more oddities Worf begins to notice about him: Kahless seems to have a lot of gaps in his memories. He knows the stories that have been written down in scripture, but he can't remember the fine details that someone who was actually there would remember. He can't tell the difference between a synthesized Klingon drink and a real one, even though it should be obvious to anyone who's drank it. And when Gowron finally confronts him, and they engage in combat...he loses. Gowron hands the Klingon Messiah his ass in front of all his followers, and then just smugly strolls away.
Kahless himself is shocked by the outcome, while the priests try to run damage control. And Worf has finally had enough: he demands to know what's going on here, or else he's gonna just kill them all. Finally, Koroth relents and tells the truth:
The Kahless sitting in the room with them right now is a clone, grown from some blood the order has carefully preserved. His memories are artificial, implanted from scripture, including a few passages kept secret from the general public by the priesthood (like the batl'eth origin story), just to make him more authentic. Clone!Kahless himself is confused and disturbed: he believed he really was Kahless, and he genuinely wanted to help his people regain their former glory. Indeed, the priests of Boreth had the best of intentions: they saw the corruption in the Empire, and they thought if they gave the people a figure to unite behind, things would get better.
Now in on the secret, Worf ponders what he should do: stand with the priests of Boreth in service to a well-intentioned lie, or expose them as frauds. He visits the makeshift shrine that Clone!Kahless established in the ship's holodeck, and realizes that not even seeing their Messiah defeated was enough to shake the faith of his followers. The Klingons' need to believe in something greater is just that strong...and perhaps just that dangerous. Gowron may be right, but so is Koroth.
Worf gets all the interested parties together and offers a solution: install Clone!Kahless as Emperor. The Klingon Empire being something of a representative oligarchy, the Emperor would have no political power whatsoever (in fact, the seat's been vacant for three centuries) but he could serve as a spiritual guide. After all, Koroth has a point: the Empire is in trouble. Worf knows better than anyone how corrupt things have become, and he knows that they could all use a reminder of what they were supposed to be. And even though he's not the real Kahless, this clone, who is basically the walking incarnation of Klingon scripture, could be his Rightful Heir.
Gowron agrees to this, begrudgingly, and everyone goes their separate ways. Worf returns to active duty, with the blessings of Kahless the Second, secure in the knowledge that he's living by Kahless's teachings.
Tropes Features in "Rightful Heir" include:
- Armor-Piercing Question: Gowron fires off a string of these at Kahless (in true Gowron fashion) after he quotes a well-known story from scripture. Kahless's inability to answer them starts the plot to unravel:"What was his name? If you were really there, you should be able to tell us the name of the man outside the walls. Describe him to us. What was he wearing? How tall was he? What color WERE HIS EYES?!"
- Call-Back: When our heroes are trying to figure out what exactly Clone!Kahless is, one possibility is a coalescent life-form.
- Clone Degeneration: It's not spelled out, but this seems to be the reason that Clone!Kahless absolutely sucks at single combat, despite the reputation of the original as the greatest warrior of them all. Either that, or the scriptures were exaggerating a few things...which is also not impossible.
- Reality Ensues: It's also likely that while he knows the technical side of fighting, as a newly awakened clone he lacks the built up fitness or trained reflexes that someone who has fought most of his life would have, with martial arts training involving repetition of the same moves over and over until one can do them without thinking.
- Clone Jesus: The basic plot.
- Crystal Dragon Jesus: Kahless is essentially the Klingon Jesus. In fact the central mythos around Kahless (created a new moral philosophy, promised to return one day, his followers united a huge chunk of their people under the beliefs he founded, etc.) is remarkably similar to that of Christianity. Kahless is basically what would happen if Jesus had been born on a Death World where He had to become the ultimate badass rather than the Prince of Peace.
- Did You Just Punch Out Cthulhu?: Gowron beats Kahless, the purported greatest warrior of all time, in a Klingon Knife Fight. Gowron. Which is clearly a sign that something's not right.
- Fantastic Drug: Implied. It's never specified what Worf is doing to try and alter his mental state, but it involves inhaling some kind of smoke, and he does look somewhat stoned when Riker comes to check on him. Presumably the worshipers on Boreth are doing the same; it's pretty damned hazy in that temple.
- Foreshadowing: Koroth's concerns about the corruption eating away at the heart of the Klingon Empire prove to be prophetic, as later seasons of Star Trek: Deep Space Nine will attest.
- The Fundamentalist: Koroth's sect has shades of this: they took Kahless's last words quite literally and are waiting for him in orbit around the star he pointed to. On the other hand, when his plan is exposed Koroth tries to invoke some fairly impressive Loophole Abuse: the scriptures all said Kahless would return; they didn't specify how. Nobody specifically called, "no cloning."
- Ham-to-Ham Combat: Gowron versus Kahless, which eventually breaks out into actual one-on-one combat. It's a wonder any scenery survived.
- Kicked Upstairs: Rather than killing Kahless' clone or letting him usurp the chancellorship, Worf suggests appointing him as Emperor, inspiring the people to return to true Klingon ways. He'd have no political power, but would be considered Kahless's rightful heir.
- Kneel Before Frodo: When Kahless II accepts his position as a placeholder for the real Kahless, every Klingon kneels to him. Including Gowron.
- Kung-Fu Jesus: Well, Space Viking Jesus.
- O.O.C. Is Serious Business: Worf not showing up for a duty shift is enough to alarm Riker.
- Tomato in the Mirror: Clone!Kahless has this reaction to learning the truth: he genuinely believed he was Kahless and genuinely wanted to continue Kahless's work. Learning he's just a clone is traumatizing, especially since he's something of a Fish out of Temporal Water (the original Kahless lived during the Klingon equivalent of the Middle Ages) and he doesn't even know what a clone is. Worf's bitter explanation, "They grew you in a glass tube, like a fungus," doesn't help much.
- We Can Rule Together: Clone!Kahless wants Worf by his side as he forges a new Klingon Empire.
- What Happened to the Mouse?: The episode ends implying that Clone!Kahless will have a fair amount of indirect influence on the direction of the Klingon Empire, but he's barely ever mentioned after this episode.
- Clone!Kahless does get his own eponymous novel later on, where we find that he's actually a clone of Kahless' best friend. Notable, also, that said best friend did most of what the historical Kahless is acredited doing.
- Star Trek: Online has Kahless the Emperor being instrumental in defeating the Legions of Hell who show up as Giant Space Flea from Nowhere but gets himself killed trying to slay an Iconian. Worf's opinion of the man is a Damning With Faint Praise and basically sends the Player Character to save him repeatedly.
- You Cannot Kill An Idea: The main reason Gowron agrees to the compromise to install Clone!Kahless as Emperor. He originally thought that being able to defeat Kahless in single combat for all his loyal followers to see would be enough to destroy their faith. When that turned out to not be the case, he figures that at least this way he and Kahless can appear to be on the same side and they can mitigate any unrest between their factions.Gowron: Kahless has been dead for a thousand years...but the idea of Kahless is still alive. Have you ever fought an idea, Picard? It has no weapon to destroy, no body to kill. The idea of Kahless' return must be stopped here. Now. Or it will travel through the Empire like a wave...and leave nothing but destruction behind.