The Reality of Illusion-Star Trek Original Series Adventure

Kirk's present mission is to investigate the disappearance of a Vulcan Science team. However, the mission takes a backseat as Kirk begins to fear an evil presence is stalking him. As Kirk's mental stability becomes worse he finally goes to see Dr. McCoy. However, before the results are back from Kirk's exam the Enterprise is forced into orbit around the planet where the Vulcans vanished. Kirk and the away team beam down, yet there is no sign of life, only a barren planet, which terrifies Kirk. Back on the Enterprise Kirk's brain scans reveal that he is going insane, but before the information reaches the landing party, Kirk vanishes leaving no clues behind.