K'Ehleyr travels to the Enterprise to inform Worf of two vital facts: that Klingon leader K'mpec has been poisoned by one of the two contenders for leadership of the Klingon Council, and that Worf is the father of her young son, Alexander, who has accompanied her to the ship. Before he dies, K'mpec asks Picard to arbitrate the power struggle between Gowron and Duras, the two Klingons vying to become his successor. K'Ehlyr learns that one of the two men has a duplicitous connection to the Romulans, but she's unable to identify the traitor until she learns the truth behind Worf's discommendation a year earlier- a delay that will imperil her life.
The starshipEnterprise is met by a KlingonVor'cha class battlecruiser, and Ambassador K'Ehleyr (Suzie Plakson) requests to speak to Captain Picard (Patrick Stewart) on an "urgent matter". When she beams aboard, she brings a young Klingon boy (Jon Paul Steuer); based on his previous romantic experience with K'Ehleyr, Lt. Worf (Michael Dorn) suspects the child is his son. K'Ehleyr warns the senior staff of a power struggle occurring within the Klingon Empire and implores Picard to meet Chancellor K'mpec (Charles Cooper) aboard the battlecruiser. On the Klingon ship, K'mpec acknowledges that he has been poisoned and is slowly dying, and insists that Picard become the Arbiter of Succession and identify his assassin. K'mpec dies shortly afterward. In a private moment, K'Ehleyr confirms to Worf that the Klingon boy is his son, Alexander, and she did not tell Worf for fear he would try to have a deeper relationship with her; Worf, already burdened by his discommendation, fears for Alexander's future, given the stigma of his family name.
The two challengers for leadership of the council, Gowron (Robert O'Reilly) and Duras (Patrick Massett), arrive for the Rites of Succession. Worf still harbors hatred for Duras, who had (falsely) revealed Worf's father, Mogh, as a traitor in the Khitomer massacre and stained Worf's family name. Both Gowron and Duras attempt to quickly end the proceeding, but a small explosion erupts in the assembly hall. Picard and K'Ehleyr are safe but decide to draw out the Rites using an archaic ceremony while the Enterprise crew perform a forensic analysis on the explosion. Though both resent the longer form, Gowron and Duras have little choice but to agree to continue the Rites.
The Enterprise crew discover that the explosion came from a Romulan bomb worn by one of Duras's guards. K'Ehleyr, aboard the Enterprise, has become intrigued and tries to find out why Worf was discommended. She accesses the Klingon records, and comes across evidence of Duras's father being the true traitor in the Khitomer massacre. Duras, notified of K'Ehleyr's access to the records, transports aboard the Enterprise and mortally wounds her. Worf soon discovers K'Ehleyr, dying, just in time for her to reveal that Duras is her killer; then she has Worf promise to look after Alexander. Returning to his quarters, Worf grabs a bat'leth, leaves his combadge behind, and transports to Duras's ship. There he challenges Duras to the Right of Vengeance, declaring that K'Ehleyr was his mate, and (since any Klingon, even one discommended like Worf, can claim vengeance), the two engage in a battle to the death. Worf gains the upper hand, but Duras taunts him - if Worf kills Duras, Worf can never regain his honor. Worf nonetheless strikes the killing blow. With Duras dead and no other challengers present, Gowron is named Chancellor of the Empire.
After the Klingons leave, Picard takes Worf to task for killing Duras. Though Worf defends his actions as valid under Klingon law, Picard reminds him he is first of all a Starfleet officer and places a formal reprimand on Worf's record. Worf and Alexander mourn their loss, and Worf places the boy in the care of his own adoptive parents, Sergey and Helena Rozhenko.