To solve the utmost mystery, the Enterprise must return to where Kirk's five-year mission began.

FAN NOTE: This is a follow up episode to "Where No Man Has Gone Before" (s1e03), the second pilot for the original series. This episode has characters called "espers". In the original series pilot, Mitchell said, "Man cannot survive if a race of true espers is born."

FAN NOTE: The Romulan Commander character was introduced in the original series episode "The Enterprise Incident" (s3e02). The actress who played that role in the original series is the mother of the actress playing the Romulan Commander in this episode.