When a crewman from a landing party investigating the latest planet visited by the Enterprise returns under some form of exterior control and then dies, Kirk decides to beam down and see for himself what caused the death. What Kirk, Spock and McCoy find on the surface is a house of horrors right out of ancient Earth mythology, right down to three hideous witches delivering a prophecy of doom for the crew. Two aliens are found to be at the heart of the evil activities, and they have no intention of letting Kirk or the Enterprise leave their world.
