A woman's image kills crew members as the Enterprise is flung beyond known space.
Kirk, McCoy, Sulu and a geologist beam down to a strange planet, and moments later the Enterprise is hurled almost a thousand light years away. On the surface, a woman named Losira appears and kills with a touch, singling out her victims one at a time.
Aboard the ship, Spock takes command while Scotty fights sabotage that threatens to overload the engines after Losira's image kills a crewman in engineering. The landing party learns that Losira is a projection of an automated defence system left by her long-dead people, the Kalandans, who were wiped out by disease. Destroying the computer ends the threat.