Worf gets an unexpected visit from his younger brother Kurn, who arrives on the station drunk and brandishing a knife. Kurn is released into Worf's care. When Kurn wakes in Worf's quarters he confronts Worf about the dishonor Worf has brought upon the House of Mogh after rejecting the Klingon Empire's war with the Cardassian Empire. Worf acknowledges what has happened but would debate it with Kurn. As a result of Worf's choices, his house has been disbanded, its land and ships all seized. Kurn was consequently ejected from the High Council and dishonored. Kurn has lost everything he cared about and has lost all honor and Worf has taken it away without suffering the consequences. Now he wants Worf to give him back his honor the only way he can, by having Worf ritually kill him. Worf begins the ceremony, but Jadzia Dax realizes what Worf is planning when she runs into Odo and finds out that the Klingon who came to see Worf was his brother as well as the incense that he purchased. She and Odo rush to interrupt the ceremony but Kurn has been stabbed, Dax quickly has herself and Kurn beamed to the Infirmary and Dr. Bashir manages to save him. Captain Sisko is furious and forbids that Worf complete the ceremony and reminds both Dax and Worf that he has given them both a lot of leeway with regard to Klingon ritual and says frankly that he has reached the limit of what he will allow.
Worf visits Kurn where Kurn tells Worf that he is not truly Klingon. Kurn points out that despite initiating the ceremony, Worf did not threaten and vigorously fight Dax and Odo to continue the ceremony, nor did he come ready to kill Kurn in the infirmary. Kurn, without an honorable life or death, places himself in Worf's hands. Dax visits Worf to apologize for stopping the ceremony and Worf says that she acted as she felt was right and that that was honorable. Worf asks Dax for advice about what to do next as Worf believes that Kurn will need something to do with his time. At Dax's suggestion, Worf asks Odo for a favor and gets Kurn a position with Odo's Bajoran security force. However Kurn loses his position when he allows himself to be shot without any attempt to defend himself.
A subplot throughout the episode is mysterious explosions accompanied by cloaked Klingon birds of prey near Bajoran space. One of the Klingon warbirds suffers severe damage and is forced to dock at Deep Space Nine. Eventually it is discovered that the explosions are due to malfunctioning mines, and that the Klingons are mining the space around Deep Space Nine in preparation for a future war. Worf proposes to Kurn that they go undercover to discover the mine locations and activation codes on the docked bird of prey. Worf appeals to Kurn's sense of family and the idea that this will discourage Gowron's ambitions (which Kurn agrees will ruin the empire). The mission is at first successful, and with Kurn's up-to-date knowledge of the Klingon military they are able to access the files, but they are interrupted by a Klingon officer. Worf pretends that he has a superior rank and seems to be able to send the officer away, but once Worf turns his back Kurn shoots the officer. Worf is shocked, but Kurn shows that the man was bringing a knife. Kurn's intense depression is enhanced by the fact he killed a man attacking in defense of the Empire. Worf gives the information to Sisko, but he is disillusioned by the fact that he was not able to realize the Klingon officer was going to kill him - feeling that a real Klingon would have. He comes to the conclusion that he is not of the Klingon or human world, but he only has his Federation rank, and Kurn has nothing at all. Worf has no idea what to do, since he no longer feels able to exercise Klingon honor and kill his brother, but Dax offers him a solution.
Worf finds Kurn drunk in his quarters contemplating suicide, a solution he would welcome were it not so dishonorable. Kurn reveals to Worf that while he never understood his brother, he always considered him honorable in his own way and that his greatest regret was that they were separated. At this point, Kurn is so drunk that he passes out. Meanwhile on the Defiant, Major Kira detonates the mines and flushes out the cloaked birds of prey. Worf talks to Dr. Bashir, revealing that they are wiping Kurn's memory and giving him a new identity. Julian warns Worf that Kurn will not remember him and will only have the most basic skills and knowledge to live among Klingons and that the process cannot be reversed. Kurn - now "Rodek" - is then entrusted to a family friend who agrees to take him in as a son. Kurn has lost all memory and accepts the situation. In the last scene he looks to Worf and asks him, "Are you my family too?", to which Worf replies: "I have no family."