Star Trek TOS Season 3

 

The Tholian Web Season 3, Episode 9

IMDB: "While Capt. Kirk and the derelict USS Defiant apparently lost, the Enterprise grapples with an insanity causing plague and an attack by the Tholians." (more)

All Our Yesterdays Season 3, Episode 23

IMDB: "When Kirk, Spock, and McCoy investigate the disappearance of a doomed planet's population, they find themselves trapped in different periods of that world's past.". (more)