Star Trek The Original Series - 36 - Strangers from the Sky

In the twenty-first centruy humanity has united after countless years of warfare, and turns toward the stars. But when an alien spacecraft crashlands in the South Pacific bearing visitors from another world, the Vulcans, Earth must decide whether to extend the hand of friendship, or the fist of war.

In the distant future, horrible dreams torment Admiral James T. Kirk, dreams prompted by his reading of Strangers From the Sky, a book about that historic first contact. He dreams of an alternate reality where he somehow changed the course of history, and destroyed the Federation before it began.