Anton took care so that his daughter never learned of his past identity as Kodos. However, not only did Lenore learn the truth, but she also became determined to silence all those who could connect her father to his past life. Some time prior to 2266 Lenore began killing those who could identify her father, including Donovan Eames and possibly Eliana Moulton as well. (TOS episode: "The Conscience of the King")
In 2266, the Karidian Company visited Planet Q and while there, Lenore took the opportunity to assassinate Thomas Leighton, one of the last few people still alive who could identify her father as Kodos. However, before his death, Leighton had told his old friend, Federation Starfleet officer Captain James T. Kirk of the starship USS Enterprise of his suspicions that Anton Karidian was in fact Kodos the Executioner.
Although initially sceptical, Kirk did begin his own investigation upon Leighton's death and arranged to have Enterprise ferry the actors to their next destination, calling in a favor from his old friend Jon Daily, captain of the Astral Queen, the company's original transport, in the process. While aboard the Enterprise, Lenore tried, unsuccessfully, to assassinate another member of the crew, Lieutenant Kevin Riley, but his survival was kept a secret and when she tried to kill Kirk with a phaser, her father stepped in front of him at the last moment. The realization that she had killed the one man she had spent all her life trying to protect destroyed what remained of her mind; she was taken into medical custody. (TOS episode: "The Conscience of the King")
By 2288, Lenore had been rehabilitated and was part of a group of volunteers that was helping rebuild on the planets Pavak and Oyolo. However, she came under suspicion when two delegates were murdered with an overloaded phaser, much like she had once used against Kirk, and an overdose of zetaproprion, the medication that Lenore was using to maintain her sanity. However, despite the accusations of now-Ambassador Kevin Riley and Lenore's own concerns that she had suffered a psychotic break of some sort, Kirk eventually determined that the true killer was Colonel Demme Gast, a Pavakian who objected to the planned peace. Although Lenore nearly handed herself over to the planets' governments to save the conference in the belief that she had been responsible, the truth was explained to her in time for her to destroy a stolen protomatter warhead- Gast having sabotaged the Enterprise to prevent it doing so- while she herself was saved at the last minute by Spock and Scotty in a shuttle. (TOS novel: Foul Deeds Will Rise)