Episode Title: "CATSPAW"
Production Number: 30
Original Air Date: 10-27-67
After a landing party is late checking in while exploring Pyrus Seven, an uninhabited planet, Lt. Jackson beams up to the ship and immediately dies, with Lt. Sulu and Lt. Commander Scott still missing on the planet. An alien voice warns Captain Kirk that there is a curse on his ship, and that the Enterprise must leave.
Leaving Assistant Chief Engineer DeSalle in command, Captain Kirk, Commander Spock, and Dr. McCoy beam down to the planet to search for Scott and Sulu. They encounter three witches and find an old castle, surrounded by fog, where they detect life-form readings. Inside, they encounter a black cat and cobwebs. After falling through a hole in the floor, the landing party finds itself chained up in a dungeon with a skeleton. Scott and Sulu appear, but they are under alien control.
Two humanoids named Korob and Sylvia tell the landing party to leave the planet, but Captain Kirk wants to investigate further, despite the aliens' warnings. Spock speculates that the aliens created the frightening environment by reading the landing party's subconscious minds, but are unable to read their conscious thoughts.
Korob and Sylvia come from a world without sensation in another galaxy, and they are disoriented by their new humanoid bodies and feelings. They want Kirk's knowledge of humanoid life in this Galaxy, but Kirk refuses to cooperate. He destroys the transmuter, the source of the aliens' power, and their illusions vanish; their humanoid forms are replaced by their true fragile forms, which quickly die, leaving the landing party free of their control.
Factoid: Trick-or-treat is an old Halloween custom on Earth.
Dr. McCoy: "The man is dead."
Guest Characters: Lt. DeSalle, Lt. Kyle, Lt. Leslie
KEY: [brackets]=illusions *star=first appearance