Lenore Karidian was born in 2247. Though Anton took care that his daughter never learned of the fact he had previously been a brutal executioner named Kodos, she not only did so, but also became determined to silence all those who could connect Karidian to that past, by murdering them. Lenore wanted to perform since the first time she saw her father act.
In 2266, shortly after Thomas Leighton began to suspect that Anton Karidian was the otherwise-believed-dead Kodos, Leighton – who was one of nine eyewitnesses to an order of execution given by Kodos when he had been governor of the Tarsus IV colony – was murdered while walking home from town. By that time, Lenore was being courted by the commanding officer of the USS Enterprise, Captain James T. Kirk, who found Leighton's body while with her. The recent murder deepened Kirk's suspicions to the point that he contrived that the company would be forced to rely on his starship for transportation, so that he could widen his investigation.
Indeed, Lenore beamed onboard the Enterprise and requested that Kirk provide transport to Benecia. As "payment" for passage, Lenore agreed that the company would perform Shakespeare's Hamlet for the crew. Captain Kirk remarked that having the acting troupe perform would be a welcome diversion for the crew. The captain, for his part, made a veiled remark about getting the chance to continue enjoying her beauty and charm. While the troupe was aboard, Lenore's romantic involvement with Kirk developed further, at one point likening herself to Cleopatra worshiping "a Caesar of the stars."
With Leighton's death, only two of the nine original eyewitnesses remained alive, and both of them served aboard the Enterprise. Lenore first attempted to poison Kevin Riley. She failed because Riley was speaking to someone at the time the poison took effect; help was promptly dispatched. She next hid an overloading phaser in Kirk's quarters, in an attempt to blow him up. This, too, failed; Kirk found the phaser and jettisoned it into space before it exploded.
During the Hamlet performance, Lenore played the role of Ophelia. Meanwhile, Kevin Riley sneaked backstage with the intent of murdering Kodos, the man who had murdered his family. Kirk was able to stop him, but Kodos overheard their sotto voce conversation. Backstage, Lenore discussed it with her father – revealing, to his horror, that she had been, over time, murdering all those who could recognize him, and planned to kill the last two after the performance. When Kirk confronted her, she snatched a phaser from a nearby guard and raced on-stage. Clearly insane, she attempted to kill Kirk, instead hitting and killing her father when he jumped in front of Kirk at the last second. This act destroyed what remained of her mind; she was taken into medical custody. (TOS: "The Conscience of the King")
Lenore Karidian was portrayed by Barbara Anderson. She shares the record (with Ricardo Montalban and Joan Collins) for the most costumes worn in a single TOS episode by a guest star (six). She wears a maroon-colored dress for her Lady Macbeth costume, a blue dress with a veil at the cocktail party thrown by the Leightons, a fur mini-skirt dress when arriving on the Enterprise, a greenish multicolored mantle on the observation deck, a black and red evening dress when Kirk visits the Karidians in their quarters, and, finally, a yellow and lavender Ophelia costume. It could even be argued that a veil she wears while walking with Kirk, just before discovering Tom Leighton's body, could be considered a seventh costume.
In the final revised draft script of "The Conscience of the King", Lenore was simply described thus; "She is beautiful." A later stage direction defined her as "wafting charm and perfume and graceful feminity."
In scripted but ultimately unused dialogue, Lenore said to Kirk, when he asked if she enjoyed her work, "I'm an actress... and I'm acting. But... to play the classics, in these times, when people prefer star-video... it isn't always as rewarding as it could be." In another line of scripted but ultimately dropped dialogue, Kirk secretly told Spock that Lenore, unlike her father, was to be granted the freedom to roam the Enterprise, as much as regulations allowed.
Lenore was also featured in a deleted scene from "The Conscience of the King", while she was on the Enterprise's observation deck with Kirk. In the scene, Lenore related to him that she suspected Yeoman Janice Rand didn't like her, believing Rand was likewise attracted to Kirk, something Lenore said she couldn't blame Rand for. Lenore meanwhile regarded Kirk as naive about women but "an exceptional man." After he complimented her in return by calling her "a very unusual woman," she replied, "Perhaps I am." Lenore then wondered if, with the advent of space travel, people still felt how they had done when they had only had one world, which Kirk confirmed. Lenore said she personally felt it was comforting to know people could still fall in love. She approached him and they shared a small kiss. Though he asked if that was meant as "a rehearsal," she stated, "A performance, dear captain," and they then embraced in a more passionate kiss. ("Swept Up: Snippets from the Cutting Room Floor", Star Trek: The Original Series - The Roddenberry Vault special features) In the final version of the episode, only the second of the two kisses is shown on-screen.
Lenore Karidian also featured in a full scene which was scripted but ultimately omitted, in which she comforted her father "almost maternally" in his quarters, where he had been anxiously pacing, waiting for her to return. She ignored him asking her where she had been, instead simply telling him she was there now. She gently eased him onto his bed, recommending he have a nap.
Lenore appeared again in the novel Foul Deeds Will Rise, when she encountered Kirk while the USS Enterprise-A was acting as the location of crucial peace talks between two planets on the verge of a major disarmament program. Although officially rehabilitated and now working as part of a group of volunteers helping the planet to rebuild, Lenore came under suspicion when two of the delegates – one from each side – were killed in a manner that implicated her; one was killed by the exploding phaser technique that she had attempted to use against Kirk and another suffered an overdose of zetaproprion (β), 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 one of the delegates attempting to use Lenore as a convenient scapegoat. Although she briefly attempted to hand herself over to the planets' governments to save the conference, Lenore later, once the truth was revealed, redeemed herself of her past crimes by risking her life to destroy a stolen protomatter warhead after the killer attempted to sabotage the Enterprise to prevent it doing so.