"The Conscience of the King" is the 13th episode of the first season of the American science fiction television series Star Trek. Written by Barry Trivers and directed by Gerd Oswald, it was first aired on December 8, 1966. The episode takes its title from the concluding lines of Act II of Hamlet: "The play's the thing/Wherein I'll catch the conscience of the king." In the episode, Captain Kirk crosses paths with an actor suspected of having been a mass-murdering dictator 20 years earlier. Plot The USS Enterprise is called to Planet Q by Dr. Thomas Leighton, a friend of Captain Kirk's, ostensibly to investigate a possible new synthetic food source. Leighton's true motivation, however, is his suspicion that Anton Karidian, the leader of a Shakespearean acting troupe currently on the planet, is in fact Kodos the Executioner, former governor of the Earth colony of Tarsus IV. Kodos had ordered that half the population of 8000 be put to death during a food shortage (supply ships were late and it was believed the full population would not survive until they arrived). Both Leighton and Kirk were eyewitnesses. Kirk insists Kodos is dead, but reconsiders after researching Karidian's background. Hoping to meet Karidian at a party at Leighton's home, Kirk meets his daughter Lenore. During a walk outside, the two find Leighton dead. Kirk arranges for the Enterprise to ferry the acting troupe to its next destination. He transfers Lt. Kevin Riley to Engineering, after discovering that he, too, was a witness to the Tarsus IV massacre. These actions arouse the curiosity of First Officer Spock who, after an investigation of his own, learns the history of the massacre, Kirk and Riley's connection to it, and that seven of the nine witnesses to the massacre have died, in each case when Karidian's troupe was somewhere nearby. Riley is poisoned, and a phaser set on overload is left in Kirk's quarters. Kirk confronts Karidian with his suspicions. Karidian does not admit to being Kodos, but argues in defense of Kodos's actions, and when asked to read a transcript of Kodos's execution order, does so with barely a glance at the paper. A computer analysis of his voice results in a near-perfect match with Kodos, but Kirk still hesitates to accuse Karidian. Lt. Riley, recovering in sickbay, overhears Dr. McCoy's log entry and learns that Karidian is suspected of being Kodos. Riley heads