Kirk is contacted by Dr. Leighton, a friend from the Tarsus IV colony years ago, who believes that Kodos the Executioner — the militant dictator who executed half of the people on the colony — is at large once more in the guise of touring Shakespearean actor Karidian.

Arnold Moss (Anton Karidian)
Barbara Anderson (Lenore Karidian)
DeForest Kelley (Dr. Leonard H. McCoy)
Grace Lee Whitney (Yeoman Janice Rand)
Nichelle Nichols (Lt. Uhura)
William Sargent (Dr. Thomas Leighton)
Natalie Norwick (Martha Leighton)
David Troy (Lt. Larry Matson)
Karl Bruck (King Duncan)
Marc Adams (Hamlet)
Bruce Hyde (Lt. Kevin T. Riley)

• Leighton, Kirk and Riley are the only remaining three (of only nine people) who actually saw Kodos. Spock discovers the other six all died when the Karidian Players were somewhere near. Riley's parents were killed on Tarsus IV by Kodos.
  
• Lenore is actually the killer. She killed Leighton, then tried to kill Riley.
  
• When Lenore tries to kill Kirk with a phaser, Anton moves to protect him and she kills her father.
  
• In the rec room, Uhura plays Spock's lute and sings a song to Riley, who is bored and alone in the engine room.