The crash of the survey ship SS Columbia on Talos IV in 2236, which left Vina as the only survivor in the care of the Talosians.
The loss of the Columbia is the background to The Cage and The Menagerie. The survey ship came down on Talos IV eighteen years before the Enterprise's visit in 2254. The Talosians found one person alive, a woman named Vina, who was terribly injured. They repaired her body without knowing what a human should look like.
When Pike's Enterprise picks up a distress signal, a landing party finds a camp of elderly scientists and a beautiful young woman. All of it is illusion, staged to lure a healthy human male as a mate for Vina.
Pike is seized and tested with fantasies. In the end Vina shows him her true appearance and explains why she cannot leave. Discovery returns to her in If Memory Serves, and Pike rejoins her at the close of The Menagerie.