"The Darkness and the Light" is the 109th episode of the television series Star Trek: Deep Space Nine, the 11th episode of the fifth season. It premiered on January 6, 1997.

Kira is shocked and saddened when Latha Mabrin, a fellow member of the Shakaar Resistance Cell-turned Vedek, is murdered.

Kira's shock turns to fear, however, when she receives a recorded message moments after learning of the murder. Her message consists of a picture of Latha appearing on the computer screen, and a scrambled voice saying simply, "That's one." Odo is unable to trace the message, which Kira interprets as a threat to all the former members of the Shakaar Resistance Cell. Kira makes arrangements to transport resistance member Fala onto a runabout returning to the station. But something goes wrong during the transport, and Fala is killed.

After what's left of the dead woman's body is removed, an investigation of the transporter reveals that Fala was killed by a tiny detonator programmed to scramble the transporter beam. A message from the scrambled voice saying "That's two" is soon delivered on a PADD. Later, while working on the case in Odo's office, Kira receives a "That's three" message displaying the face of Mobara, another member of the Shakaar. Immediately, they begin efforts to contact him, hoping to stop his murder. Kira returns to her room in O'Brien's quarters to rest, but is jolted by a loud crash outside her door.

Phaser drawn, Kira creeps into the living room, ready to face the assassin. Instead, she comes face to face with Furel and Lupaza, two more members of the Shakaar who have come to help her. Thinking her bodyguard was the killer, they attacked him — causing the noise Kira heard. Furel and Lupaza volunteer to hunt down the assassin for Kira. She prefers to handle her problem within the boundaries of the law, but allows Furel and Lupaza to stay with her in the O'Brien quarters to "protect" her and the O'Briens' unborn child. Later, the grim, but not unexpected, news of Mobara's death arrives. During a staff meeting, Odo surmises that whoever is doing the killing most likely has a vendetta against Kira — and that she is also a likely target. Nog, Dax and Kira work with the scrambled voice, hoping it will provide a clue, but the voice used in the messages turns out to belong to Kira. Their work is interrupted by news that there has been an explosion in the O'Brien quarters. O'Brien was not home at the time, but Furel and Lupaza are dead.

...
Wikipedia