Plot summary
Captain Kirk orders shore leave for the Enterprise crew on a seemingly uninhabited planet in the Omicron Delta system. The landing parties begin to see strange sights, such as a White Rabbit a la " Alice in Wonderland ", Don Juan, and a sword-wielding samurai. Also, Kirk sees (and fights) an image of Finnegan, a rival from his Starfleet Academy days. Spock discovers that the planet seems to be drawing a large amount of energy from the ship's engines, placing the Enterprise in danger.
Credits
Adapted from Wikipedia contributors, Star Trek: The Original Series season 1. HTML formatting and reference markers removed.