2-26: Assignment: Earth
After traveling back to 1960s Earth, the Enterprise accidentally beams aboard a time-traveling secret agent.
2-01: Amok Time
When Spock exhibits irrational behavior from pon farr, The Enterprise heads to Vulcan for help.
2-16: The Gamesters of Triskelion
Kirk, Uhura, and Chekhov are abducted and forced into combat games with other captives.