1-25: The Devil in the Dark
The Enterprise encounters a silicone-based life-form who is attacking pergium miners.
1-28: The City on the Edge of Forever
After following a delusional McCoy into 1930s Earth, Kirk must make a heart-wrenching choice to save the future.
1-26: Errand of Mercy
Kirk and Spock try to protect a seemingly primitive species from a Klingon invasion.