"Crossover" is the 43rd episode of the science fiction television series Star Trek: Deep Space Nine, and the 23rd episode of the second season. This episode was written by Peter Allan Fields and Michael Pillar, and directed by David Livingston. It aired on broadcast television on May 16, 1994. Set in the 24th century, the series follows the adventures on Deep Space Nine, a space station located adjacent to a stable wormhole between the Alpha and Gamma quadrants of the Milky Way Galaxy, near the planet Bajor. In this episode, first officer Kira and Doctor Bashir have an adventure in Star Treks Mirror Universe, a parallel universe setting introduced in the episode "Mirror, Mirror" of the original Star Trek series. It is the first of five Deep Space Nine episodes to involve the Mirror Universe. Plot After experiencing operational difficulties while traveling through the wormhole, Major Kira and Dr. Bashir find themselves in an alternate universe populated by exact doubles of the people in their own universe. In this universe, the wormhole is unknown, and Terrans (i.e., humans) are slaves; Deep Space Nine is a mining station run by the Intendant, Kira's counterpart, with Garak as her second in command and Odo overseeing the Terran slaves. As Bashir is sent to work in ore-processing, the Intendant tells Kira about James Kirk's visit to this universe a century ago; that incident led to the formation of a powerful alliance between the Klingons, Cardassians, and Bajorans, and the eventual conquest of the Terrans. Bashir tries to talk Miles O'Brien, a fellow slave, into configuring the transporters to help Kira and Bashir return home, but the beaten, put-upon O'Brien is unwilling to risk the wrath of his superiors. Meanwhile, Kira almost succeeds in securing help from the bartender Quark, but he is arrested and executed by Garak for helping Terrans escape the station. Kira meets Benjamin Sisko's Mirror Universe counterpart, who receives better treatment than the other Terrans for carrying out piracy on behalf of the Klingon-Cardassian alliance. The Intendant assures Kira that she has nothing to fear, and suggests they should become closer. Later, Garak tells Kira that he intends to kill the Intendant, and that he will let Kira and Bashir escape if she impersonates the Intendant and yields power to Garak; Bashir will be killed if she does not comply. Kira tells Bashir they must find a way back to