"The House of Quark" is the 49th episode of the science fiction television series Star Trek: Deep Space Nine, the third episode of the third season.

Quark is assaulted in his bar by a drunk Klingon named Kozak, and in the scuffle Kozak accidentally stabs himself dead. Quark pretends to have slain Kozak in self-defense so as to attract more customers with his newfound notoriety. A Klingon named D'Ghor, claiming to be Kozak's brother, accosts Quark in private and extracts the truth, and intimidates Quark into maintaining his lie of self-defense because an accidental death would embarrass the family.

Kozak's widow, Grilka, visits Quark's bar and abducts him. Quark awakens on the Klingon homeworld of Kronos, in the home of Kozak's family. Quark sheepishly admits that Kozak's death was an accident. Grilka's advisor explains that Kozak was the head of his family and left no male heir, and had his death been ruled an accident his widow would have exceptionally been allowed to take over the family, but since Kozak's death was ruled honorable the House of Kozak is leaderless and defunct. D'Ghor is not Kozak's brother and is actually from a rival family to which the House of Kozak is heavily in debt. In desperation, Grilka forcibly marries Quark, making him the new head of Kozak's family, which legally prevents D'Ghor from seizing her property.

Quark inspects the family ledgers and discovers that D'Ghor has for years been using financial tricks to weaken the House of Kozak's assets à la in a makeshift Klingon Ponzi scheme. This is dishonorable conduct for a Klingon, and when Quark exposes D'Ghor's actions before Chancellor Gowron, D'Ghor in turn exposes Quark's lie regarding the circumstances of Kozak's death. D'Ghor challenges Quark to a duel to the death, and to everyone's astonishment Quark shows up for the fight. Quark throws his weapon to the ground, and denounces the duel as no better than an execution since Quark is no warrior. D'Ghor is happy to kill the unarmed Quark. Gowron, disgusted by D'Ghor's conduct, aborts the duel and dicommendates D'Ghor on the spot. Gowron, after complimenting Quark for showing extraordinary bravery, rules that there are enough "unusual circumstances" to grant Grilka special dispensation to lead her dead husband's family. Quark asks the grateful Grilka for a divorce, which she happily and immediately grants. However she kisses him afterwards, hinting she still has feelings of romance for him.

In this episode's subplot, Keiko O'Brien feels bored and useless since she closed her school due to lack of students. Her husband Miles convinces her to go on a botanical expedition to Bajor. She takes their daughter Molly with her, leaving Miles alone on the station.

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