Star Trek: Deep Space Nine Season 2 Episode 19 Blood Oath

When a trio of legendary Klingon warriors arrives on Deep Space Nine, Jadzia Dax is shocked to discover that Kor, Koloth and Kang have not only come to pay their respects to a fallen comrade, but also to ask Dax to fulfill a blood oath that they swore with her previous host, Curzon. In exchange for teaching Curzon the ways of a Klingon warrior, he swore to assist the trio in their quest for vengeance against a long-dead enemy of the Klingon Empire. Despite protests from Sisko and the rest of the crew, Dax decides to accompany the Klingons on their mission, forcing them to confront the bonds of brotherhood and the consequences of their actions. Meanwhile, Kira and O'Brien discover a secret holosuite program that Quark has been using to run an illegal gambling ring. As tensions between the Klingons and Dax mount, Sisko is faced with the difficult decision of whether or not to intervene, and how far he is willing to go to preserve the delicate balance of power on the station.