Quark is having a problem. There's a drunken Klingon in his holosuite who refuses to leave until he's won a recreation of a historic battle. He enlists Odo for help, and the Klingon turns out to be Kor, much older than when we last saw him, and piss drunk. Odo convinces him that his victory celebration awaits him and manages to lure him to the drunk tank. A second Klingon arrives to claim Kor, who else is it but Koloth. And if that's not enough, Kang joins them. All three Klingons have come to be reunited for a final mission, but they didn't realize that Dax was onboard. Curzon Dax was a close friend of theirs and wants in on whatever they've got cooking.
It turns out that years ago, a Klingon criminal known as "the Albino" was raiding Klingon colonies. Kor, Koloth, and Kang, were sent to stop his raids, but the Albino escaped and swore vengeance on their firstborn sons. He made good on this threat, killing all three of their firstborn sons including Kang's son Dax, of whom Curzon Dax was godfather. Curzon joined the three Klingons in swearing a blood oath to kill the Albino someday, but he's always evaded them. Now Kang has found his location and got Kor and Koloth together for an attack.
Dax is conflicted. She knows that Trills typically do not carry over commitments from their past lives, but she still feels Curzon's outrage and desire for justice for the murder of his godson. She asks Kira about her experiencing killing during the Bajoran war for independence. Kira doesn't want to talk about it, so Dax comes clean about her reasons. Kira warns her that killing will also cause a piece of yourself to die as well. But Dax decides that she still wants in. She confronts Kor, who is busy boozing and whoring it up at Quarks, and convinces him to let her join. But he warns her that Koloth and Kang are unlikely to change their minds.
Dax finds Koloth practicing his impeccable bat'leth skills in the holosuite. She engages him a sparring session and does pretty well for herself before getting disarmed and bested. Koloth admires her warrior spirit and gives his blessing, but he warns her that Kang is dead-set against her. Dax argues that Kang has no right to deny her vengeance, so Kang angrily relents, telling her to come with them and "be damned."
Dax requests a leave of absence, but Kira has blabbed Dax's intentions to Sisko, who is furious. He denies Dax's leave and tells her that she cannot take justice into her own hands and start murdering people. Dax counters that by Klingon law, her intentions are legitimate. Sisko is unmoved, telling her that if she leaves, she may not find her position waiting for her when she returns. She leaves anyway.
En route to the Albino's stronghold, the gang ponders their approach. The Albino is holed up with dozens of guards. They discuss a clandestine approach, but Kang is adamant that they make a frontal assault for glory. All four state gravely, "It is a good day to die," but once the others have left, Dax confronts Kang on his determination to make a seemingly suicidal attack. Kang admits that he has already spoken to the Albino, who promised his pursuers a noble end to their vendetta if they will fight 40 of his guards in toe-to-toe combat. Weary of the chase, Kang agreed. However, Dax convinces him that an honorable victory is superior to an honorable death.
On the Albino's planet, the foursome stake out the Albino's compound and discover that the planned meeting ground has been covertly mined, so the Albino never intended to honor his deal after all. The gang stages a commando raid through the Albino's defenses until the Albino calls a general alarm. There's a huge brawl in the Albino's main command center, during which both Koloth and Kor are injured. Kang engages the Albino is single combat, but his bat'leth breaks, and the Albino deals him a mortal blow. Dax moves forward to strike down the now-helpless Albino, but she cannot bring herself to kill him. Kang revives long enough to stab the Albino in the back before dying. With Koloth dead of his wounds, only Dax and Kor remain alive. Kor begins singing a Klingon dirge.
Back on the station, Dax finds her post unfilled. Kira and Sisko shoot her cold glances but make no move to stop her from returning to her work.
- The Alcoholic: Kor has become one, to the disgust of his friends, particularly Koloth.
- Badass Boast: When Koloth arrives in Odo's office without being seen.Odo: How did you get in here?Koloth: I am Koloth.Odo: That doesn't answer my question.Koloth: Yes, it does.
- Bittersweet Ending: The mission is a success, and Jadzia is spared from having a murder on her conscience by Kang. But two of her good friends are dead, and once she's back at the station, Kira and Sisko just can't look at her the same way.
- Bloodless Carnage: The bat'leth is employed liberally against the Albino and his guards by Dax and the Klingons, but not a drop of blood is to be seen.
- Blood Oath: It's right there in the title. Kor, Koloth, Kang, and Curzon Dax swore a blood vow to capture and kill the Albino for killing their firstborn sons (or, in Curzon's case, his godson Dax, who was Kang's child). They've spent decades hunting him down, and Jadzia feels compelled to complete the oath even though Trill culture states she has no obligation to her past lives.
- Call-Back: Kang mentions the Klingon restaurant from Melora and Playing God in citing the decline of his culture.
- Continuity Cavalcade: Three of the most prominent Klingons to appear in TOS come back and unite for one last mission.
- Cornered Rattlesnake: The Albino is a Dirty Coward who uses dishonorable tactics and cowers behind his goons, but once his goons are all dead and he's forced to go one-vs-one against Kang, he actually proves to be quite a skilled opponent and actually manages to break Kang's weapon and fatally wound him.
- Cut His Heart Out with a Spoon: "I will cut his heart out and eat it while he watches me with his dying breath!" This doesn't exactly happen, unless it's off-screen.
- Deal with the Devil: Invoked word for word in Kang making a deal with the Albino. Appropriate, given what happened in the original episode he starred in the Original Series.
- A Death in the Limelight: For Koloth and Kang
- Dirty Coward: When confronted by the four vengeance-seekers, the Albino thrusts his consigliere in front of him.
- Dirty Old Man: Kor doesn't mind Dax being an attractive young woman. He really doesn't mind.
- Disappointed in You: Sisko and Kira's cold glances at Dax in the final scene indicate their disapproval of her actions, but they make no move against her.
- Domestic Abuser: Kang says he located the Albino from one of his "discarded wives", who feared her husband so much she'd only reveal his location in a message left after she died.
- Exact Words: Odo's justification for turning off the holosuite while a drunk Kor is inside, despite Quark's objections. Kor threatened to kill Quark, after all.
- Expy: In creating the characters of the three Klingons as they are now, Kor was inspired by William Shakespeare's Falstaff, while the other two are from The Magnificent Seven (1960) — Koloth after James Coburn's Britt and Kang after Yul Brynner's Chris.
- Faceless Goons: It saves time and money on funny rubber foreheads.
- Famed in Story: When Koloth states that he is a Dahar Master, Odo immediately adopts a respectful tone.
- The Glomp: On seeing Dax is now in the body of a beautiful woman, Kor demands a kiss. He gets a hug instead.
- Going Native: Curzon Dax made a blood oath despite being a Federation ambassador. Far from being just a political move to get the Klingons on side, Dax takes the oath so seriously she continues it as Jadzia Dax.
- Good Old WaysKang: The old Klingon ways are passing. There was a time, when I was a young man, the mere mention of the Klingon Empire made worlds tremble. Now, our warriors are opening restaurants and serving racht to the grandchildren of men I slaughtered in battle.
- Grumpy Old Man: Koloth and Kang.
- He Knows Too Much: Dax worries that the traders Kang spoke to might have warned the Albino. He replies that they'll never warn anyone ever again.
- How the Mighty Have Fallen: Dax reminds Kor of his past triumphs, leading to a rare moment of sobriety.Kor: The only weight I carry now, dear comrade, is my own bulbous body. I was once, if you remember, far less than you see, and far more than I have become.
- I Gave My Word: Interesting variation on this with Dax, as her previous host Curzon gave his word to avenge the death of his godson (Kang's son). Even though she's not required to uphold her previous host's promises, Jadzia goes through with it.
- Inadequate Inheritor: Although Kor accepts the new Dax right away, Jadzia has to prove herself to Koloth and Kang.
- Instant Death Stab: When Kang uses a dagger to stab the albino in the back at the climax, the albino instantly and wordlessly drops dead.
- Irony: Kang dies fighting in a burning house.
- It Works Better with Bullets: Dax works out a Techno Babble means of deactivating the disruptors of the Faceless Goons, so they have to rely on hand weapons.
- Killed Off for Real: Kang and Koloth die of their injuries.
- A Lady on Each Arm: Which leads to a dilemma when you're got a jug of blood wine in front of you.
- Leeroy Jenkins: Kang can't come up with a better strategy than "Attack! Attack! Attack!", prompting Jadzia to peg him as a Death Seeker.
- Legendary in the Sequel: The three Klingon captains Kirk faced are living legends by now.
- Loophole Abuse: Although Klingon blood oaths are forever, Kang wants to let Dax out of theirs, since Curzon was the one who swore the oath and Jadzia is an entirely different person. Nothin' doin'.
- Lured into a Trap: The Albino has secretly contacted Kang, offering him a chance for a glorious death in a battle with forty of his mooks. Turns out there was actually a large bomb under the place where this fight is supposed to take place. Fortunately Dax makes Kang tell the truth and comes up with another option.
- Mundane Made Awesome: Koloth is shown cutting his food with exact strokes of his knife, just to show how he's constantly maintaining his skills.
- Mythology Gag: When Kor pulls open the holosuite doors, the sound effect of doors opening from The Original Series can be heard. Fitting, considering Kor was a prominent antagonist back during Kirk's time as captain of the Enterprise.
- No Name Given: The villain is only ever referred to as the Albino.
- No Sympathy: When Quark complains about Kor threatening to kill him, Odo gives a mock "Awww..."
- Not Too Dead to Save the Day: Kang is fatally wounded in the final confrontation, but he turns out to have enough life left in him to get back up and kill the Albino when Dax is unable to do it, before dying properly.
- Outliving One's Offspring: Cruelly invoked by the Albino, who took vengeance on Kor, Koloth, and Kang by killing each of their firstborn sons.
- Papa Wolf: Kor, Koloth, and Kang are ultimately driven by this trope—the Albino deliberately used a virus to kill each of their firstborn sons as revenge for them thwarting his raids. Curzon Dax was also involved, as he served as godfather to Kang's boy.
- Pre-Asskicking One-Liner: Delivered to the Albino courtesy of Kang.Kang: Look upon your executioners, killer of children!
- Red Right Hand: The villain is an albino Klingon simply called "the Albino."
- Releasing from the Promise: Kang and several others try their best to convince Jadzia that she has no part in Curzon's oath. But she refuses to release herself.
- Retired Badass Roundup: Dax has to work at getting all three Klingon legends to support her joining and to work together for one last glorious battle.
- Revenge Before Reason: According to Trill tradition, Dax has no obligation to anything promised by a past host, in fact Trill society dictates near-total disconnect from past lives, and the Klingons aren't pressuring her either.
- Screw the Rules, I'm Doing What's Right!: Jadzia's way of justifying herself to Sisko.
- Something Only They Would Say: Jadzia convinces Kor of her previous identity as Curzon Dax by making comments about the old Klingon's anatomy that only a close friend would know.
- Space Pirates: The Albino led a bunch of these before Kor, Koloth, and Kang put a stop to his operation.
- Stating the Simple Solution: When the four are wondering whether the Albino is actually in his compound, Koloth declares that he will go and find out. Kor asks how, and Koloth snaps, "I'll ask somebody!" (Of course, he's implied to be rather... forceful with his questioning.)
- Status Quo Is God: Sisko promises dire consequences for Jadzia and her future in Starfleet should she disobey his orders and go after The Albino. When she returns, Sisko and Kira shoot her dark looks but allow her to work at her station. Nothing is ever made of the incident. The very next episode starts with Kira cheerfully inviting Dax to dinner.
- Stealth Expert: Koloth is one. He manages to sneak up on Odo as well as around the Albino's base.
- Strike Me Down with All of Your Hatred!: With the Albino mocking Dax while her bat'leth is at his throat. Kang mistakes her lack of resolve for her letting him land the death blow himself. (Doesn't he?)
- Sword over Head: Dax balks at killing the Albino. Ironically this is mistaken for Only I Can Kill Him by Kang, who stabs the Albino In the Back while he's mocking Dax's lack of resolve. Kang then thanks Dax for allowing him to strike the death blow.
- Vitriolic Best Buds: Koloth, towards Kor. On seeing him drunk in Odo's holding cell, his immediate response to give up and leave. Even his last words are him refusing to die before Kor.
- Would Hurt a Child: In the past The Albino avenged his ruined plans by infecting the firstborn sons of Kang, Koloth, and Kor with a fatal virus.
- Wrecked Weapon: Kang has an Oh, Crap! moment when his bat'leth shatters while fighting the Albino.
- You Can Keep Her!: Koloth goes to bail Kor out of Odo's cells, but is so disgusted by the drunken wretch he walks off and leaves him there. Fortunately Dax overhears Odo complaining about him and convinces Odo to release him into her custody.