The infamous words that Spock
spoke to Captain Kirk
in the Star Trek
episode The City on the Edge of Forever
. Has gone on to become a metaphor for one single tangible injustice righting many intangible ones. The subject of obscure references in many places, including country songs, and at least one episode of FreakyLinks
In the episode, Kirk and Spock find themselves in New York City, searching for Doctor McCoy in 1930. While lying low, Captain Kirk falls in love with the social worker Edith Keeler. Spock discovers that the timeline has been altered, and that Edith Keeler is the cause. In the original timeline, she was killed in a traffic accident. But in the bad timeline, she goes on to found a pacifist movement, meeting with FDR, and delaying the United States's entrance into World War Two. Because of that, Germany won the war because they developed atomic bombs first, and conquered the world.
So when Spock tells Captain Kirk of this, he ends with, "Jim... Edith Keeler must die."
Kirk wrestles with this, and in the end, throws himself in front of McCoy when he tries to save Keeler from an oncoming car.
The moment was one of the most dramatic in Star Trek history, one of the defining moments of Kirk's character, and is said to be the moment at which many people stopped thinking of Star Trek as just a kids' show.