2-01: Amok Time
When Spock exhibits irrational behavior from pon farr, The Enterprise heads to Vulcan for help.
2-06: The Doomsday Machine
Dispatched to investigate the destruction of several planets, the Enterprise encounters the badly damaged U.S.S. Constellation.
2-05: The Apple
In paradise-like surroundings, a landing party encounters a primitive race controlled by Vaal - a machine revered as a God.