The Conscience of the King (Episode)
Kirk suspects a Shakespearean actor is a mass murderer.
Captain Kirk receives a message summoning the Enterprise to the home of Dr. Thomas Leighton, a brilliant research scientist whom Kirk knew many years before. The summons is a trick to lure the captain to Planet Q so that he could see and meet actor Anton Karidian. Leighton believes that Karidian is actually Kodos, the ex-governor of Tarsus IV, who oversaw a massacre that killed the doctor's entire family and part of Kirk's as well. When Leighton is killed, Kirk investigates and decides to transport the Karidian troupe on the Enterprise so that he can study the enigmatic actor. In an effort to discover the truth, Kirk romances Karidian's daughter, Lenore. During the voyage, Lieutenant Kevin Riley, another survivor of the massacre, is poisoned and nearly dies. A phaser explodes, almost killing Kirk and Spock. Riley recognizes Karidian as Kodos, but a shocked Kirk discovers the insane murderer of the survivors is Lenore—who accidentally kills her father.