The Looking Glass War Summary . A Bolian transport prepares to depart Deep Space 9 , when the wormhole flares open , and a severely - damaged emerges . Considering the ship is currently docked at DS9 , its appearance is met with shock by the senior staff . With the ship on the verge of a warp core breach , O ' Brien beams the sole occupant to the infirmary . Commander Sisko is shocked to discover that the pilot of the " Defiant " is none other than Curzon Dax , who died over four years earlier . Curzon reveals that he comes from a parallel dimension – and needs Odo ' s help to avert all - out war between the Federation and the Dominion . Curzon explains that negotiations had been set up between the two sides , after the Dominion made overtures of peace – Curzon had been sent as the Federation ' s chief negotiator . However , the talks soon broke down , and a force of Jem ' Hadar fighter s swarmed through the wormhole and attacked DS9 . Although eventually repelled by a Starfleet task force defending the station , heavy casualties were suffered , and that universe ' s versions of Sisko , Kira and Bashir taken captive . With another assault imminent , Curzon – assisted by that universe ' s O ' Brien – modified the " Defiant " to travel between dimensions via the wormhole . After encountering numerous universes – including the mirror universe – Curzon came across ours , the first in which existed the person he was looking for – Odo . In his universe , Odo had been murdered by persons unknown , causing the peace talks to collapse . Curzon needs Odo ' s help in impersonating his counterpart , in order to find the killer and prevent the invasion of the Alpha Quadrant . However , Sisko believes that any intervention would violate the Prime Directive , and forbids Odo to go . He orders Curzon confined to quarters until he can be returned to his own dimension . Curzon manages to gain access to the station ' s access tunnel s , incapacitate Odo , and steal this universe ' s " Defiant " , firing on DS9 in the process . Using the station ' s access codes against the crew , he escapes into the wormhole . Curzon emerges in his own dimension , with the now reconstituted Odo , who demands to be taken back . However , when Curzon tells him that is no longer possible , Odo agrees to go along with the subterfuge , appearing before a stunned Lt . Commander Eddington . Odo and Curzon begin investigating the murder , taking time to give Quark " the shock of his misspent life " . Examining the corridor where the alternate Odo was apparently slain , Odo notices an unusual residue pattern on the floor . In his quarters , he finds an identical smear on his bucket , which holds a Bajoran flame plant – a plant which , on first encounter , causes a painful rash to spread on the victim . Noone on the station has reported such a rash – a fact which doesn ' t surprise the Changeling . Having repaired Curzon ' s " Defiant " , the DS9 senior staff enter the wormhole and make the dimensional transit . Upon entering the other universe , they find their " Defiant " heading straight at them . As it cloaks , both ships emerge in the Gamma Quadrant , to face a large force of Jem ' Hadar ships . Sisko orders their cloak to be engaged , but a fluke hit causes them to reappear , allowing the Jem ' Hadar to tractor the ship in . O ' Brien and Jadzia are ordered below , so that it appears as if the other universe ' s captives have escape . The Jem ' Hadar , pursued by Odo and Curzon , take the " Defiant " to a cloaked base over Callinon VII . Odo disguises himself as a Jem ' Hadar , as the captured DS9 crew encounter the counterpart of the Jem ' Hadar they recovered earlier that year . The alternate " Defiant " crew , with the disguised Odo , beam onto the station , and encounter O ' Brien and Dax while taking control of a medical lab , the two almost killing Odo with a phaser blast . The two crews get to work on a chemical of unknown description – a plan independently devised by both Odo and Bashir . Meanwhile , Sisko , Kira and Bashir manage to overpower their guards during the attack , and free their counterparts . They reinforce the others at the lab , as Dax completes the chemical , a derivative of the isogenic enzyme found in ketracel - white , which incapacitates the station ' s crew . With both crews returned to their correct ships , and heading back to DS9 , Odo reveals who his counterpart ' s murderer was . To prevent Bajor from being overrun following the peace accord , Kira killed Odo in his quarters and transported the remains in his bucket to where they were found . Since Kira had been raised on Bajor , she would not have contracted the rash from the plant in the bucket . Kira seizes control of the other " Defiant " , and orders her crew into the ship ' s escape craft . The " Defiant " takes the escape craft in a tractor beam , and pulls it through the wormhole , activating their transdimensional drive only seconds before the self - destruct sequence destroys the other " Defiant " and that universe ' s wormhole . Memorable quotes . " " . . . treachery , like hope , springs eternal . Even as we offered the Dominion the hand of peace , their hands carried knives — to stab us in the back . " " " " Good evening , all . Try to hold the quadrant together without me . " " " " Oh , no . . . " " " " . . . two of them ! " "