“The Darkness and the Light” is episode eleven of season five of Star Trek: Deep Space Nine.
At a Bajoran religious ceremony, one of the priests is killed by something that had been turned into a weapon. Odo informs Major Kira of this, because the dead man was a friend of hers and a member of the Shakaar resistance cell, of which Kira was a member. The dead man, before turning to religion, had not been a very nice person, and had made a lot of enemies. The murder is considered to be related to that – until Kira gets a message that just has his face whilst a distorted voice says ‘That’s one.’
Another friend of Kira’s contacts her, and Worf and Dax head to pick her up. The teleport goes wrong, and the woman – also a member of the same cell as Kira – dies. She had been implanted with a device intended to mess up transports. Another message is received, this time saying ‘That’s two.’ It seems someone is targeting the members of Kira’s cell, and rubbing it in her face. They would appear to be trying to make a point. Presumably, they will move onto Kira after all of her friends are killed.
As another member has gone missing, Odo contacts the Cardassians for information and Kira’s fellow cell members Furel and Lupaza – seen in “Shakaar” – come to the station to help. The attacks are presumably related to something the resistance cell did, and to an attack in which Kira was intimately involved.