The Enterprise travels to the planet Elba II, home of the last asylum for the criminally insane, to deliver a serum that should cure all of its remaining inmates. Kirk and Spock beam down to the planet's surface where all seems in order, but they soon find the inmates now run the asylum, led by Garth (at one time a starship Captain, whose exploits were required reading at the Academy). Garth, who's learned how to shape-shift, can take on the appearance of anyone, including Kirk or Spock. In the process of learning this ability, he lost his sanity. Garth plans to pose as the Captain, beam up to the Enterprise and take over the ship, but Kirk has a roadblock set up to overcome. Written by
Did You Know?
Leonard Nimoy complained to the producers that the story's climax was unbelievable that Spock would have had so much difficulty who the real James Kirk is. For instance, Spock is a close friend of the Captain and could have easily posed personal trick questions that only the real Kirk could have answered properly. See more
During the seduction scene between Marta and Kirk, Kirk is alternately lying down or sitting halfway up. See more
How could you, a starship fleet captain, believe that a Federation crew would blindly obey your order to destroy the entire Antos race, a people famous for their benevolence and peaceful pursuits?
That was my only miscalculation.