1-25: The Devil in the Dark

An incident on the edge of the galaxy transforms two crew members, one of whom is a long-time friend of Captain Kirk.

The Enterprise encounters a silicone-based life-form who is attacking pergium miners.

Enterprise awakens a dangerous group from suspended animation.

On a planet resembling 1960s Earth, all of the adults have perished from a deadly disease.

Kirk and Spock try to protect a seemingly primitive species from a Klingon invasion.