While hosting her first Trill initiate, Dax discovers a tiny, expanding protouniverse that threatens to destroy the entire Bajoran system.

Three legendary Klingon warriors reunite on DS9 seeking Curzon Dax, with whom they entered into a blood oath to one day exact revenge on their sworn enemy. Finding Jadzia to be as worthy a warrior as they felt Curzon to be, they invite her to join them on their crusade.