Dax's old Klingon friends call in a debt.
Three aging Klingons from Curzon Dax's past, Kor, Koloth and Kang, arrive at the station. Decades earlier a criminal known as the Albino killed their firstborn sons, including Kang's son, who was Curzon's godson, and they swore a blood oath with Curzon to kill him. Kang has found him at last, and Jadzia insists on honouring the oath.
Sisko does not approve but does not stop her. Dax learns that the Albino has offered Kang a glorious but hopeless last stand and comes up with a plan to disable the Albino's energy weapons. In the fight Koloth is killed, Kang is mortally wounded but kills the Albino before he dies, and Kor survives with Dax.