Through the Looking Glass (Star Trek: Deep Space Nine)

Sisko is abducted and taken to the Mirror Universe, which Kira Nerys and Julian Bashir visited the year before, by Miles O'Brien's Mirror Universe counterpart. This O'Brien explains that Sisko's counterpart, the leader of the Terran (i.e., human) rebellion against the Klingon–Cardassian Alliance, has been killed. Jennifer Sisko, the Mirror counterpart of Sisko's late wife, is a scientist working for the Alliance, building a device that will allow the Alliance to discover the rebels' headquarters; Sisko must impersonate his counterpart and convince Jennifer to join the rebels, or the rebels will kill her. Unwilling to let Jennifer die again, Sisko agrees to intervene. He meets the rebels, including Mirror counterparts of Bashir, Rom, Jadzia Dax, and Tuvok.

Terok Nor, the Mirror Deep Space Nine, is a brutal Alliance mining station run on Terran slave labor, ruled by Intendant Kira. Jennifer Sisko, who despises her ex-husband, is working under Kira's supervision, believing that the bloodshed against the Terrans will end once her device is completed. Rom, seemingly betraying the rebellion, informs Kira that Benjamin Sisko is alive, enabling Alliance forces to capture him and O'Brien and take them to Terok Nor.

Kira sends O'Brien to ore processing with the slaves, and takes Sisko to her quarters. When Sisko meets Jennifer, he apologizes for his counterpart's past treatment of her, and tries to convince her that the Alliance is her real enemy. Sensing he may be winning her confidence, Sisko signals O'Brien using communicators concealed under their skin. In ore processing, O'Brien receives the signal and causes a malfunction that allows him and the Terran slaves to escape. Meanwhile, Jennifer agrees to leave with Sisko; they meet O'Brien and head for a waiting ship.

Before they can escape, however, they are cornered by Kira and her troops, who have killed Rom upon realizing that he was a double agent working for Sisko. Sisko and his group retreat to the ore processing center and seal themselves within. When Kira and her soldiers force their way in, Sisko tells her that he has activated the station's self-destruct sequence, which only he can stop. Kira reluctantly agrees to let Sisko, Jennifer, O'Brien, and the Terrans go free in order to halt the imminent destruction. Back at the rebel encampment, Jennifer admits to having realized that he's not really her husband. She kisses Sisko goodbye before he returns to his universe.

There were five Mirror Universe episodes of Star Trek: Deep Space Nine; "Crossover", "Through the Looking Glass", "Shattered Mirror", "Resurrection", and "The Emperor's New Cloak".[1]

This episode uses a Star Trek story element introduced in The Original Series episode "Mirror, Mirror"[2] which aired on October 6, 1967.

In 2017, SyFy ranked this the third best Mirror Universe episode of Star Trek, with Sisko being captured by people from the Mirror Universe.[3] This episode introduced Mirror Jennifer, who returns later in the series in the episode "Shattered Mirror" as well as Mirror Universe versions of various series' regulars.[4]

• "Shattered Mirror" (Continues the Mirror Universe narrative)

• "Through the Looking Glass" at IMDb

• Through the Looking Glass at Memory Alpha (a Star Trek wiki)

• Through the Looking Glass at StarTrek.com