STAR TREK: #5 The Enemy Within, 1966

Writer: Richard Matheson
Dir.: Leo Pen
Music: Sol Kaplan

Captain Kirk: William Shatner
Science Officer, First Officer, Cmdr. Spock: Leonard Nimoy
Dr. Leonard "Bones" Mc Coy: DeForest Kelly
Lt. Sulu: George Takei
Lieutenant Commander Montgomery Scott: James Doohan
Lieutenant Uhura: Nichelle Nichols
Yeoman Rand: Grace Lee Witney

Lt. John Ferrell: Jim Goodwin
Technician Fisher: Edward Madden
Technician Wilson: Garland Thompson
Kirk II: Don Eitner

Stardate: 1672:1

  Kirk, Sulu, Technician Fisher and others are on Alpha 177 while the Enterprise is in orbit. As Technician Fisher is beamed on borad some of the magnetic ore he brought along causes the transmitter to malfunction. The chief engeneer, Scotty, tests the transmitter and does not find anything wrong. He now beams the captain on borad. Soon after the two have left the transmitter room, the captain materializes again ... An animal is beamed up next. This time the crew realizes that two identical looking specimens came out from one beamed animal and they detect a difference between them: One is calm and frienldy while the other is aggressive and hostile. 

After Yeoman Rand accused the captain of having assaulted her and Spock notices a change in the captain's behavior, he knows that the same has happened to Captain Kirk. They look for the other one, who has got a scar over his face after the encounter with Yeoman Rand. As are the animals are the two Kirks. One Kirk is weak, soft, friendly, compassionate, intelligent and kind, but unable to make decisions. One Kirk is agressive, amoral, violent, egoistic and strong, but unable to behave socially. Spock suggests not to use the transmitter until all is safe and finds a captain who considers the uncoming night down there on the side of the planet where the landing party is. The night - and the cold. Without the sun, the surface becomes as cold as ice, degrees well below zero ... and the captain cannot decide what to do. 

Helpless he listens to Sulu who informs him about the decreasing temperature down there.  His other part visits Dr. McCoy, who, as he knows, has got "a supply of Saurian Brandy for medical reasons" and demands it from him. The doctor talks with Spock who shares with him: "Being split in two halves is no theory with me, Doctor. I have a human half, you see, as well as an alien half, submerged, constantly at war with each other. Personal experience, Doctor. I survive because my intelligence wins out over both, makes them live together." When the other Kirk is found, Spock does not knock him down, but uses the gentle Vulcan neck pinch to render him unconscious. 

 The time pressure is on Spock and Scotty to repair the transmitter before the landing party dies of the cold. While both sides of Kirk are dying on their own, Scotty manages to run the transmitter on impulse engines. Spock suggests to beam down both and beam them up as one again. They try with the two animals. Kirk in waiting for the result, stands by. Back comes one. McCoy says: "He's dead, Jim," and finds out that it has died of the shock and not of the transmission. Spock surmises that Kirk, being able to understand what is happening to him, should be able to survive. Now both Kirks are beamed down and up again, the captain materializes as one and orders the landing party to be rescued. McCoy: "God forbid, I should have to agree with Spock, but he was right. Without the negative side you wouldn't be the Captain, you couldn't be."