Episode Title: "LET THAT BE YOUR LAST BATTLEFIELD"
Production Number: 70
Original Air Date: 01-10-69
Stardates: 5730.2, 5730.7, 5730.6
The planet Ariannus, a vital transfer point on space commercial lanes, has been attacked by a deadly bacterial invasion. The U.S.S. Enterprise is en route to decontaminate the planet, when it encounters a stolen Starfleet shuttle piloted by an alien who is white on his right side and black on the left. The alien, named Lokai, is from Cheron, an uncharted planet in the southern-most part of the Galaxy. An alien ship with an invisibility sheath intercepts the Enterprise and Bele -- chief officer of the Commission on Political Traitors on the planet Cheron -- boards the ship, claiming that Lokai was convicted of treason and escaped.
Commissioner Bele's people on Cheron are white on the left side and black on the right, and were the master race who once oppressed Lokai's people, who have the opposite pigmentation. Bele takes control of the Enterprise in order to return Lokai to Cheron, but Captain Kirk threatens to destroy the ship, and the course to Ariannus resumes; after decontaminating the planet, Kirk plans to turn Lokai over to Starfleet at Starbase Four for stealing the shuttle, but Commissioner Bele uses his power to change course for Cheron again.
When they arrive at Cheron, they find the planet in ruins and the entire population dead; in the thousands of years that Commissioner Bele has been pursuing Lokai, their peoples have destroyed themselves. Lokai and Bele beam down to their dead world to continue their pursuit and ancient hatred of one another.
Factoid: The Enterprise is part of the United Federation of Planets, under Starfleet Command.
Factoid: Cheron is near the dark Coalsack area of the southern Galaxy.
Guest Characters: Nurse Christine Chapel
Alien Races: *Cherons
KEY: [brackets]=illusions *star=first appearance