Kirk, Spock, and McCoy have to try to escape from a planet where (almost) everyone has the power of mental domination and uses it at will and with total disregard for the dominated.
One of the best third-season episodes. Also features the Kirk/Uhura kiss.
Highlights:
Alexander
the mood
interesting/disturbing scenes
Spock’s musings/reckonings
Lowlights:
some silliness
Spockism: “Whose harmony? Yours? Plato wanted truth and beauty, and above all, justice.”