The City on the Edge of Forever
Summary
After accidentally overdosing on a powerful stimulant, Dr. McCoy becomes unbalanced and disappears through the Guardian of Forever, a newly discovered time portal on a remote planet. Kirk and Spock follow after learning that McCoy somehow changed history, removing everything they once knew, including the Enterprise. Arriving in the 1930s, the duo meets Edith Keeler, a New York social worker, who gives them a place to stay. As the days pass, and McCoy is nowhere to be seen, Kirk finds himself falling in love with Keeler, but Spock discovers that Keeler must die to restore the timeline. In 1997, TV Guide ranked this "Hugo Award"-winning episode number 92 on its list of the 100 Greatest Episodes. In 2009, it moved to #80.
Summary from Wikipedia, CC BY-SA 4.0.
Find out more
These links open the services in a new tab with the question pre-filled; the AI assistants may ask you to sign in. Their answers can contain errors.