“The Alternative Factor”
Written by Don Ingalls
Directed by Gerd Oswald
Season 1, Episodes 20
Production episode 6149-20
Original air date: March 30, 1967
Captain’s log. The Enterprise is finishing up an orbital survey of an uninhabited planet, when they’re buffeted by some kind of force. According to Spock, for an instant the magnetic field of the solar system disappeared and the planet below had no mass—it was as if reality winked out of existence for a second. As soon as the phenomenon abated, a humanoid life sign reading appeared on the planet out of nowhere.
Kirk, Spock, and a four-person security detail beam down to investigate. They find a small, one-person ship—which, weirdly, Spock’s sensors did not pick up—and its pilot, who is ranting and raving and then faints.