DS9 Season 3 Episode 5 Second Skin

Plot

Major Kira is contacted by Alenis Grem, a Bajoran archivist who has discovered a computer record of Kira's time in a Cardassian prison camp; Kira is naturally skeptical, as she was never in Cardassian detention, but the records appear authentic. Kira arranges a meeting with Alenis to examine the files personally and leaves for Bajor, but Alenis soon contacts the station to report that Kira never arrived. Cardassian ex-spy Garak receives information that Kira is in the custody of the Obsidian Order, the feared Cardassian intelligence agency, and passes it on to Commander Sisko.
Awakening in a darkened room, Kira is warmly welcomed "home" by Entek, a Cardassian official. When she looks in a mirror, she is shocked to see that she has been surgically altered to appear Cardassian. She furiously rejects the idea that she is Cardassian, but is introduced to Legate Tekeny Ghemor, an officer of Cardassian Central Command, who claims that she is his daughter Iliana. Entek explains that she is a sleeper agent, altered to appear Bajoran and embedded in Bajor as part of a long-term covert operation.
Ghemor is upset that his "daughter" doesn't remember him, but is reassured by Entek that her memory will return, given time. Kira is upset and incredulous, especially when she is shown the preserved body of the "real" Kira Nerys. She declares the dead girl's body a fake, but begins to doubt her own memories, especially after viewing a video message recorded by Iliana before her mission.
After several escape attempts, she is interrogated by the Obsidian Order, but she refuses to provide them with information. Eventually, Ghemor, still believing her to be his daughter, offers to help her escape the harsher interrogation she will certainly suffer at the hands of the Order, revealing himself as a member of Cardassia's underground dissident movement. In a moment of insight, Kira realizes that the entire affair — her abduction, her "Cardassian" identity, her supposedly blocked memories — were all staged in an attempt to reveal Ghemor as a dissident.
Odo, Garak, and Sisko arrive in time to prevent the Order from taking Kira and Ghemor away for punishment. Garak shoots Entek, after remarking that "treason is in this eye of the beholder." Back at Deep Space Nine, tests reveal that Kira is definitely Bajoran. Ghemor understands that she is not really Iliana, but declares that he will never stop hoping that Iliana is alive and will return to him.