Originally aired October 27, 1967. When Kirk and his landing party arrive on the planet below, they are met by eerie mists, a dark castle, witches, goblins and a black cat. They soon learn that they are under the influence of a wizard, Korob, who tries to bend them to his will. They also soon learn that the black cat they saw is more than she appears and is in fact a powerful witch in her right. It is left to Kirk and Spock to find a means to escape their grasp.
View the full episode here on YouTube.