In "Prodigal Daughter", Ezri returns to her family home on the planet New Sydney, in the Sappora system, after Sisko asks her to investigate the disappearance of Chief Miles O'Brien ( Colm Meaney ). There she finds that her family are involved with the Orion Syndicate , and discovers that her brother Norvo ( Kevin Rahm ) murdered the person that O'Brien was searching for.  The Mirror Universe episode " The Emperor's New Cloak " showed an unjoined Ezri Tigan, who is in a relationship with both the alternative Kira Nerys (Nana Visitor) and Leeta ( Chase Masterson ). During the course of the episode, Tigan kills the mirror-Garak, in revenge for the death of Brunt ( Jeffrey Combs ).  The remaining episodes of the season are set in the main universe, with the following episode "Field of Fire" exploring Ezri's use of the memories of Joran Dax ( Leigh McCloskey ) — who had previously been revealed as a murderer in the third season episode " Equilibrium ".   She uses those memories to track down a Vulcan serial killer on the station.